CREDITS
micro
5
biology 2013 BATCH
C R
BHAGATH M S
O
M E
P V
L I
E
T E
E W
RAJEEV BISWAS
Contents Sl no 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32
Chapters Preface (Introduction) Morphology and Structure of Bacteria Physiology of Bacteria Disinfection and Sterilization Bacterial Genetics and Variation Bacterial Infection and Immunity Principles of Diagnosis and Prevention of Bacterial Infection Coccus Enteric Bacilli Vibrio Campylobacter Jejuni and Helicobacter Pylori deleted Anaerobic Bacteria Corynebacterium Mycobacteria Parvobacillus Zoonotic Bacteria Other Bacteria Actinomyces and Nocardia Spirochetes Chlamydie Mycoplasmas Rickettsia General Properties of Viruses Multiplication and variation of viruses Viral infection and immunity Diagnosis of viral infection Prevention and treatment of viral infection Hepatitis viruses Respiratory viruses Enteroviruses GASTROENTERITIS-RELATED VIRUSES Herpesviruses Retroviruses and Cancer Associated Viruses Encephalitis Viruses Hemorrhagic Fever Viruses Other Important Viruses General Properties of Fungi Pathogenic Fungi PAGE 1
6. Preface (Introduction to Microbiology) REVIEW QUESTIONS 1. What is the difference between Prokaryotes and Eukaryotes? PROKARYOTES
NO Nuclear membrane NO Histones NO membrane-enclosed organelles Divide by BINARY FISSION
EUKARYOTES
Nuclear membrane Histones Organelles Divide by MITOSIS
2. What is the Koch’s postulates? Koch’s postulates are :: 1. The microbe must be found in the body in all cases of the disease. 2. It must be isolated from a case and grown in a series of pre culture in vitro. 3. It reproduces the disease on the inoculation of a late pure culture into a susceptible animal. 4. The microbe must be isolated again into pure culture from such experimentally caused infection.
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7. Bacteria morphology and Structure REVIEW QUESTIONS 1. What is the difference between Gram+ bacteria and Gram- bacteria cell wall ? 2. What is the difference between Gram+ bacteria and Gram- bacteria peptidoglycan? 3. What are the specific structures of bacteria? and their functions? 1. WHAT IS THE DIFFERENCE BETWEEN GRAM+ BACTERIA AND GRAM- BACTERIA CELL WALL ? GRAM + BACTERIA GRAM - BACTERIA 1) single membrane 1) Double membrane (Inner and outer) 2) Multiple layers of peptidoglycans 2) Single layer of peptidoglycan 3) Techoic & lipoteichoic acids 3) Lipoproteins 4) Polyribitol & Glycerol phosphate 4) Lipopolysaccharide 5) Antigenic determinant 5) Porins Actinomyces, Bacillus, Corynebacterium, Campylobacter, Chlamydia, Enterobacter, Clostridium, Enterococcus etc Escherichia, Helicobacter, etc
2. WHAT IS THE DIFFERENCE BETWEEN GRAM+ BACTERIA AND GRAM- BACTERIA PEPTIDOGLYCAN? GRAM + BACTERIA GRAM – BACTERIA COMMON Multiple Single PEPTIDOGLYCAN LAYER BACKBONE N-acetyl glucosamine and NN-acetyl glucosamine and Nacetylmuramic acetylmuramic acid SIDE CHAIN A set of tetrapeptide side chain A set of tetrapeptide side chain CROSS BRIDGE A set of pentapeptide cross ---------------bridges STRUCTURE 3- diamensions stereo structure 2-diamensions plane structure STONG/ PUFF STRONG , 15 – 50 layers PUFF , 1 – 2 layers
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3. WHAT ARE THE SPECIFIC STRUCTURES OF BACTERIA? AND THEIR FUNCTIONS? Specific Structure of Bacteria capsule flagella pili spore CAPSULE a condensed，well-defined layer closely surrounding the cell，it is called the capsule. Its component is polysaccharide or polypeptide. The capsules are hard to stain directly，are demonstrated by the negative staining procedure. FUNCTIONS protect the encapsulated cells from phagocytosis. act as a barrier to antimicrobial substances in the blood，body fluids. promote adherence FLAGELLA Bacterial flagella are thread-like appendages composed entirely of protein.
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They are the organs of locomotion and provide motility for bacteria allow the cell to swim toward food and away from poisons. The types of flagella arrangement : MONOTRICHOUS :: single polar flagellum LOPHOTRICHOUS :: multiple polar flagella PERITRICHOUS :: flagella distributed over the entire cell FUNCTIONS Identification of Bacteria Pathogenesis Motility of bacteria They are highly antigenic (H antigens) PILLI Pili are hair-like projections of the cell , They are known to be receptors for certain bacterial viruses. Chemical nature is pilin Classification and FUNCTION Common pili or fimbriae: fine , rigid numerous, related to bacterial adhesion Sex pili: longer and coarser, only 1-4, related to bacterial conjugation SPORES (ENDOSPORES)
Under conditions ，some gram-positive bacteria can convert from a vegetative state to a dormant state， and form a single internal spore.
The spore looks bright ，often ovoid in the microscope.
Identification of Bacteria It is highly resistant to environment factors，such as desiccation，heat，radiation and chemical agents. A temperature of 121℃ for 15 minutes kill spores.
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ď‚Ą sterilization with autoclaves or pressure cookers are used for this purpose.
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8. Physiology of Bacteria REVIEW QUESTIONS 1.What way do Bacteria reproduce by? 2. What is Nutrient requirements of bacterial growth? 3. How many phases are there about the growth curve? 4. What are Environmental factors affecting growth of bacteria? 5.What kinds of bacteria are according to their gas requirements? 6.What are IMViC? 7. How many are bacteria anabolic products? What? 8. What kinds of mediums are Classified according to purpose ? 9. How much are Phenomena of bacterial growth In liquid medium ? 10.What is colony? What way to describe colony?
1.WHAT WAY DO BACTERIA REPRODUCE BY? most common means of bacterial reproduction forming two equal size progeny genetically identical offspring cells divide in a geometric progression doubling cell number o BACTERIA REPRODUCE BY BINARY FISSION.
Culture Increase in the population of cells
Generation time the time it takes to divide into double cell
2. WHAT IS NUTRIENT REQUIREMENTS OF BACTERIAL GROWTH? Basic bacterial requirements water carbon nitrogen other WATER Used to dissolve materials to be transported across the cytoplasmic membrane CARBON required for the construction of all organic molecules
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autotrophs use inorganic carbon (CO2) as their carbon source heterotrophs use organic carbon NITROGEN Obtained from inorganic source e.g. Nitrogen gas (N2), Nitrate (NO3), Nitrite(NO2), and Ammonia (NH3) organic source e.g. Proteins, broken down to amino acids Many organisms use nitrogen gas by nitrogen fixation to produce ammonia OTHER NUTRIENTS Required in small amounts are Iron Sulfur Phosphorus
3. HOW MANY PHASES ARE THERE ABOUT THE GROWTH CURVE? Growth of culture goes through four phases with time 1) Lag phase 2) Log or Logarithmic phase 3) Stationary phase 4) Death or Decline phase LAG PHASE Organisms are adjusting to adapt for the environment little or no division synthesizing DNA, ribosomes and enzymes in order to breakdown nutrients, and to be used for growth
Exponential growth = balanced growth
LOG PHASE ENDING LOG OR LOGARITHMIC PHASE Division is at a constant rate Cells are most susceptible to inhibitors Bacterial shape is typical.
•
due to exhaustion of nutrients
•
accumulation of toxic metabolic products
STATIONARY PHASE Dying and dividing organisms are at an equilibrium Death is due to reduced nutrients, pH changes, toxic waste and reduced oxygen
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DEATH PHASE The population is dying in a geometric fashion so there are more deaths than new cells Deaths are due to 1) factors in stationary phase 2) lytic enzymes that are released when bacteria lyse
4. WHAT ARE ENVIRONMENTAL FACTORS AFFECTING GROWTH OF BACTERIA? 1) Nutrition 2) Temperature 3) Oxygen 4) Salinity 5) pH 6) Pressure 7) Radiation NUTRIENTS Basic bacterial requirements water carbon nitrogen Other TEMPERATURE One of the most important factors optimal growth temperature???? for human pathogens Microorganisms can be categorized based on their optimal temperature requirements PSYCHROPHILE 0 - 20 ºC •
Some will exist below 0 • oC if liquid water is available • • Example :: Ocean, Refrigerators, Freezers. Is capable of growth in in food stored at refrigeration temperatures (0-8 ℃)
MESOPHILE 20 - 40 ºC Most human flora and pathogens at 37 0C But, leprosy bacillus prefer lower Temp.
THERMOPHILE 40 - 90 ºC • • • •
Hot springs Effluent from laundromat Deep ocean thermal vents Taq polymerase, the key enzyme used in the polymerase chain reaction (PCR)
Most bacteria are mesophiles especially pathogens that require 37 ºc
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OXYGEN Required for aerobic respiration and energy production Organisms are classified according to their gaseous requirements Obligate aerobes Facultative anaerobes • Halophiles growing Obligate anaerobes within salt lakes often Microaerophilic bacterium turn the water pink • this sometimes occurs SALINITY in Great Salt Lake, Utah Halophiles • Staphylococcus are salt bacteria that specifically require NaCl for growth tolerant up to Moderate tolerants concentrations of 10% grow best at 3% NaCl solution NaCl • grow on surface of skin many ocean dwelling bacteria Extreme tolerants grow well at NaCl concentrations of greater than 15% salt lakes, pickle barrels pH microbes have different optimum pH requirements ACIDOPHILES some bacteria can grow in acid substrates NEUTROPHILES most microbes prefer a pH near neutrality ALKALINOPHILES microbes which can grow in very alkaline substrate. 5. WHAT KINDS OF BACTERIA ARE ACCORDING TO THEIR GAS REQUIREMENTS? Organisms are classified according to their gaseous requirements OBLIGATE AEROBES grow only when oxygen is available FACULTATIVE ANAEROBES grow in the absence of oxygen OBLIGATE ANAEROBES require oxygen but exhibit maximal growth rates at reduced oxygen Concentrations MICROAEROPHILIC BACTERIUM The microbe require oxygen, but a level about 5%-6%, if >10% inhibit the bacterium.
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Terms used to describe O2 Relations of Microorganisms Environment Group
Aerobic
Anaerobic
O2 Effect
Obligate Aerobe
Growth
No growth
Required (utilized for aerobic respiration)
Microaerophile
Growth if level not too high
No growth
Required but at levels below 0.2 atm
Obligate Anaerobe
No growth
Growth Toxic
Facultative Anaerobe (Facultative Aerobe)
Growth
Growth
Not required for growth but utilized when available
6. WHAT ARE IMVIC ? METHYL TEST INDOL TEST
VP TEST
CITRATE UTILIZATION TEST
I M Vi C Test I
M
Vi
C
E.coli
+
+
—
—
E.aerogebes
—
—
+
+
INDOL TEST Some bacteria produce tryptophanase, which can hydrolyze the tryptophan into indole. Indole is colorless and invisible, but may reacts with dimethyl aminobenzaldehyde to form rose indole. METHYL TEST Some bacteria ferment glucose producing enough acid to effect pH change from 6.0 to 4.4. Methyl red is red. VP TEST Voges-Proskauer (VP) Test Some bacteria produce acelyl-methyl-carbiol by the fermentation of glucose in the media. A red color is developed (positive). CITRATE UTILIZATION TEST Some bacteria can utilize citrate as their carbon. The end production is NH3, which Makes the culture medium’s pH>7.
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The indicator BTB ( bromothymol blue) change color from green to blue.
7. HOW MANY ARE THERE IN BACTERIA ANABOLIC PRODUCTS? WHAT ARE THEY ? 1 pigment : Water-soluble pigment: that diffuse into the media. Lipid soluble pigment: that confined to the colonies. 2.PYROGEN This is a fever-producing substance synthesized by bacteria. 3.TOXINS AND INVASIVE ENZYMES Exotoxin: Excreted by living cell Endotoxin: Integral part of the cell wall of gram-negative bacteria. Released on bacterial death.
4. ANTIBIOTIC (BACTERIUM, FUNGUS, ACTINOMYCES) Some microorganism produce a kind of materials that can restrain or kill other microorganism. 5. BACTERIOCIN: some bacterial strains produce a kind of protein that kill the relative bacteria. 6. VITAMIN
8. WHAT KINDS OF MEDIUMS ARE CLASSIFIED ACCORDING TO ARTIFICIAL CULTIVATION OF BACTERIA ? Medium is the material prepared artificially in which or on which the bacteria are grown. Classification according to the purpose a. Essential medium Essential media: were used to culture most bacteria. b. Enrichment medium
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Growth of some pathogens was found to be dependent on such supplements, Such as blood or serum was added Essential medium. c. Selective medium Selective medium limits the growth of unwanted microbes or allows growth of desired ones. d. Differential medium Differential medium contain chemicals which permit the observer to differentiate the bacteria.
9. HOW MUCH ARE PHENOMENA OF BACTERIAL GROWTH IN LIQUID MEDIUM ? In liquid medium
sediment
turbid
Bacterial Membrane
10.WHAT IS COLONY? WHAT WAY TO DESCRIBE COLONY? Colony is made up of millions of bacterial cells derived from a single bacterium. The colonies of different types of bacteria show different characteristics. Colony observation 1.size: small、medium、large
2.Form: circular or irregular 3.Edge: entire or irregular 4.Surface: convex, flat, smooth, rough, dry or moist 5.Transparency: transparent or opaque 6.Colour: Water-soluble pigment and Lipid soluble pigment
on the Petri dish
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9. Disinfection and Sterilization REVIEW QUESTIONS 1. What are differences among Sterilization and Disinfection, Antisepsis? Sterilization Disinfection Sterilization is the process of destroying all microbial forms.
A sterile object is one free of all microbial forms, including bacterial spores.
Antisepsis
Disinfection: The reduction Antisepsis: Use of or elimination of pathogenic chemical agents on skin microorganisms in or on or other living tissue to materials. inhibit growth of microbes. Disinfectant: Products used to kill microorganisms, but Antiseptic： Products are not necessarily used to inhibit sporicidal. microorganisms
2. What kinds of Physical Agents are used to eliminate Microorganisms? I. HIGH TEMPERATURE o Dry heat o Moist heat II. RADIATION o Ultraviolet Radiation (UV) o Ionizing Radiation III. FILTRATION o Air filtration IV.LOW TEMPERATURE o Refrigerator temp (4-7oC) o Deep-freeze (-20oC to -40oC); liquid nitrogen (-196oC) V. DESICCATION o Lyophilization (desiccation in low temperature)
3. What is the most useful method to kill vegetative organisms and spores? Aldehydes is the most useful method to kill vegetative organism o denature microbial proteins Formalin (37% solution of formaldehyde gas) glutaraldehyde: kill vegetative bacteria in 10-30 minutes and endospores in about 4 hours OR
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Moist heat sterilization: 1. Autoclaving: Use steam at 121 C, for 15-20 min. It is used for killing both vegetative organisms and spores. 2. Boiling water: vegetative organisms 100 C, 2-3 min. spores at 100 C, for 5.5 hours. 3. Pasteurization: 60 C – 65 C for 30 min, for beverages such as wine, beer and milk.
4. What kinds of solutions are sterilized by Filter? The filters contain pores small enough to prevent the passage of bacteria . Liquid filtration is a process in which a membrane filter is used membrane filter contains 0.22/0.45 mm pores small enough to prevent the passage of bacteria. To sterilize solutions that may be damaged or denatured by high temperatures or chemical agents such as VACCINES, ANTIBIOTIC SOLUTIONS, ANIMAL SERA, ENZYME SOLUTIONS, VITAMIN SOLUTIONS, & so 5. Please say three kinds of methods for moist heat to sterilize bacteria (or dry heat)? Moist heat： 1) Autoclaving: steam,121℃,15-20min kill for both vegetative organisms and spores 2) Boiling water: vegetative organisms : 100 ℃, 2-3min Spores: 100°C, 5.5 hours 3) Pasteurization: 60 ℃- 65℃ 30min, food such as wine ,beer, milk 6. Please say six kinds of disinfectants. 1) PHENOL & PHENOLICS Carbolic Acid 2) ALCOHOLS 3) HALOGENS (Iodine) Tincture Aldehydes Heavy metals Acids and alkalies Salts of organic acids Undecylenic acid
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7. What factors affect disinfectant? Affecting factors for disinfectant potency are :: 1. AGENT Kinds Concentration Action time 2. BACTERIA Strain Numbers 3. CIRCUMSTANCES pH Tm Organics Affecting factors are as follows :: The concentration and kind of a agent used; The temperature and pH at which the agent is used; The number of microorganisms present; The species or strain of microorganism; The nature of the material bearing the microorganism; The presence of organic or other interfering substances.
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10. Bacterial Genetics and Variation REVIEW QUESTIONS Basic terms: I. GENE a segment of DNA (or chromosome), the fundamental unit of information in a cell II. PLASMID o Plasmids are extrachromosomal genetic elements capable of autonomous replication. o Plasmids are circular double stranded DNA carrying genetic information. III. IS o Insertion Sequences o IS: The simplest transposable elements are called IS. o IS contains the information necessary for their migration from one genetic locus. IV. Tn o Transposons are transposable genetic elements that carry Resistance genes in addition to IS o Lytic or virulent phages V. LYTIC OR VIRULENT PHAGES The phages can multiply on bacteria and kill the cell by lysis. VI. LYSOGENIC OR TEMPERATE PHAGE o They are able to enter a nonlytic prophage state in which replication of their nucleic acid is linked to replication of the host cell DNA . o bacteria carrying prophages are termed as lysogenic beacause a physiologic signal can trigger a lytic cycle resulting in death of the host cell and liberation of many copies of the phage VII. PROPHAGE o the phage DNA actually integrates into the host chromosome and is replicated along with the host chromosome and passed on to the daughter cells.
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VIII. LYSOGENIC BACTERIUM o The cell harboring a prophage is termed as lysogenic bacterium IX. TRANSDUCTION o Transduction is mediated by a bacteriophage, which pick up fragments of DNA from a donor bacteria and package them into bacteriophage particles. o The DNA is delivered to infected bacteria and becomes incorporated into the bacterial genomes. X. TRANSFORMATION o Transformation is gene transfer resulting from the uptake by a recipient cell of naked DNA from a donor cell. o the DNA that is taken up can be incorporated into the recipient's chromosome. XI. CONJUGATION o Transfer of DNA from a donor to a recipient by sex pilus contact between the cells. XII. LYSOGENIC CONVERSION o The prophage DNA as a gene recombined with chromosome of host cell
1) HOW MUCH KINDS OF BACTERIAL MATERIAL IS RELATED TO GENETICS AND VARIATION? A) Chromosomes: o Genetic information is sorted as sequence of DNA. o Most DNA molecules are double stranded. o Bacterial chromosomes usually contain 400 pairs of gene and every bacteria has only one copy of DNA. B) Plasmid: o Extra-chromosomal genetic element capable of autonomous replication. o Plasmids are irregular double stranded DNA. o The genetic information on plasmids is not essential. C) Transposable Elements: o They are mobile genetic elements that can move from one position to another in the genome or between different molecules of DNA.
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2) WHAT LIFE CYCLE ARE LYTIC PHAGE AND LYSOGENIC PHAGE RESPECTIVELY? A. Lytic life cycle of bacteriophage consists of 5 stages: 1. Adsorption: Attachment sites on the phage adsorb to receptor sites on the host bacterium. Usually they absorb pilli or flagella for attachment. 2. Penetration: A phage enzyme (drills) a hole in the bacterial wall and the phage injects its genome into the bacterial cytoplasm. 3. Biological synthesis: The phage replicates its genome and uses the bacterium’s metabolic machinery to synthesize phage enzymes and phage structural components. 4. Maturation and release: The phage part assembles around the genomes. Then, a phage-coded lysozyme breakdown the bacterial peptidoglycan causing osmotic lysis and release of the intact phages. 5. Re-infection: The newly released phages will attack other bacterium and will continue lytic cycle. B. Lysogenic life cycle consists of both lytic and lysogenic life cycle. It usually has 4 stages: 1) Adsorption: Attachment sites on the phage adsorb to receptor sites on the host bacterium. Usually they absorb pilli and flagella for attachment. 2) Penetration: A phage enzyme “drills” a hole in the bacterial wall, and phage injects it’s genome into the bacterial cytoplasm. 3) Prophage formation: The phage DNA integrates into the host chromosome, thus forming a prophage, and replicated along with the host chromosome and passed on to the daughter cells. 4) Induction: Anytime a lysogenic bacterium (the bacterium harboring a prophage) is exposed to chemicals, the lysogenic state can be terminated and lytic multiplication begins. 3) HOW MANY ARE MECHANISM OF GENE TRANSFER AND RECOMBINATION ? The mechanism of gene transfer and recombination are :: I. TRANSFORMATION II. CONJUGATION III. TRANSDUCTION IV. LYSOGENIC CONVERSION TRANSFORMATION Transformation is gene transfer resulting from the uptake by a recipient cell of naked DNA from a donor cell.
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the DNA that is taken up can be incorporated into the recipient's chromosome.
CONJUCTION Transfer of DNA from a donor to a recipient by sex pilus contact between the cells. TRANSDUCTION o Transduction is mediated by a bacteriophage, which pick up fragments of DNA from a donor bacteria and package them into bacteriophage particles. o The DNA is delivered to infected bacteria and becomes incorporated into the bacterial genomes. o Transduction :: Generalized Transduction Specialized Transduction
LYSOGENIC CONVERSION The prophage DNA as a gene recombined with chromosome of host cell.
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11. Bacterial infection and immunity REFERENCE Biological activities of endotoxins Pyrogenicity Lethal action Activation of complement Intravascular coagulation Leucocytosis Inhibition of glucose and glycogen synthesis in the liver Macrophage inhibitation Interferon release
Depression of blood pressure Leucopenia Stimulation of B lymphocytes
Induction of prostaglandin synthesis Clotting of limulus lysate (lysate of amebocytes from horseshoe crab, Limulus Polyphemus, used as a test for detected of endotoxins.)
Immunity against infectious diseases is of different types I. INNATE (NATIVE) IMMUNITY II. ACQUIRED (ADAPTIVE) IMMUNITY
Non specific
Specific
Species Racial Individual Species Racial Individual
Active
Passive
Natural Artificial
Natural Artificial
Normal bacterial flora Body Sites SKIN
NASOPHARYNX
Normal bacterial flora Staphylococcus epidermidis Staphylococcus aureus (in small number) Micrococcus species Non pathogenic Neisseria species Alpha-hemolytic and non hemolytic streptococci Diphtheroids Propionibacterium species Peptostreptococcus species Small number of other organism (candida species, Acinetobacter species) Diphtheroids Non pathogenic Neisseria species α-hemolytic streptococci S epidermidis Non hemolytic streptococci Anaerobes
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GASTROINTESTINAL TRACT & RECTUM
GENITIALIS
Yeast Haemophilus species Pneumococci S aureus Gram negative rods Neisseria meningitides Various Enterobacteriaceae except Salmonella Shigella Yersinia Vibrio and Campylobacter species Non dextrose fermenting gram negative rods Enterococci Alpha- hemolytic and non hemolytic streptococci Diptheroids S.aureus in small number Yeasts in small numbers Anaerobes in large numbers Corynebacterium species Lactobacillus species α-hemolytic and non hemolytic streptococci non- pathogenic Neisseria species enterococci enterobacteriaceae and other gram negative rods S.epidermidis Candida albicans and other yeast Anarobes
Microbial loads on “External” surface Large intestine (1014) > Skin (1012) > Vagina, Mouth, Nose, Throat (1010) Anaerobic Normal Flora (RATIO OF ANAEROBES : AEROBES) SKIN 1 : 1 LARGE INTESTINE 1000 : 1 VAGINA 10 : 1 Components of Innate and Adaptive Immunity Innate Immunity Adaptive Immunity Physical barriers Skin, gut villi, lung cilia None Soluble factors Many protein & non-protein secretions Immunoglobulins (antibody) Cells Phagocytes, NK cell, eosinophils, K cells T and B lymphocytes
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Routes of Infection o Respiratory o Gastro enteric o Genito urinary tract o Close contact
o o o o
Insect bitting Blood transfusion Parenteral route Mucous membrane
REVIEW QUESTIONS Basic terms: NORMAL MICROBIAL FLORA o There are the definite kinds and quantities of Microorganism populations . o They inhabit the body skin and the mucous membranes of the cavity that is interlinked outside. o They are favourable and harmless for person. o They are Bacteria, Fungi, Protozoa o Seen in External surface and the cavity interlinked outside. OPPORTUNISTIC PATHOGEN Opportunist an organism that can cause infection in individuals with abnormal host defences. Commensals may be opportunistic pathogens. DYSBACTERIOSIS o If flora disequilibrium occurs, some pathogenic microbes may produce diseases. o This diseases is called dysbacreriosis. EXOTOXIN The proteins are excreted by both G+ and G- bacteria, mainly G+ bacteria. ENDOTOXIN The Lipopolysaccharides complexes are a part of the cell wall of G- bacteria, released on bacteria death. TOXOID o It is a physically or chemically inactivated exotoxin by formalin, acid, heat, etc. o Toxoids are used to immunize. TOXEMIA It is the presence of exotoxins in the blood where there are no bacteria.
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ENDOTOXEMIA It is the presence of endotoxins in the blood. BACTEREMIA It is an invasion of the bloodstream by bacteria,not reproduction in bloodstream. SEPTICEMIA illness that occurs when poisonous substances (toxins) produced by certain bacteria enter the bloodstream.
PYEMIA It is caused by pyogenic microorganisms in the blood. 1. What are Beneficial effects of the Normal Flora? Normal flora may aid the host in several ways: Aid in digestion of food Help the development of mucosa immunity Protect the host from colonization with pathogenic microbes.
2. What are the conditions of Opportunistic pathogen? 1) HOST DEFENSES ARE IMPAIRED i. Immuno-suppression (AIDS & SCID) ii. Radiation therapy & Chemotherapy iii. Perforated mucous membranes iv. Rheumatic heart disease…etc. 2) If normal flora is forcefully removed from the restrictions and introduced into foreign locations, e.g., the blood stream, the free peritoneal cavity 3) Microbial flora is altered by : broad-spectrum antibiotics diet 3. What factors involve bacterial Pathogenesis ? o virulence factors o the number of microbes in invasion o pathway to invade the host Characteristics 1. Transmissibility 2. Adherence to host cells 3. Invasion of host cells and tissue • invasion of the host immune system • Toxigenicity
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4.How many substances are Bacterial Virulence factors? i. Swim ii. Stick iii. Bacterial Biofilm iv. Antiphagocytic substance v. Scavenge Nutrients vi. Stealth vii. Subvert 5.What differences are between Exotoxin and Endotoxin? PROPERTY ENDOTOXIN CHEMICAL NATURE
EXOTOXIN
Lipopolysaccharide (mw = 10kDa)
Protein (mw = 50 – 1000kDa)
Part of outer membrane
Extracellular, diffusible
No
Usually
Yes
Yes
No
Yes
Relatively low (>100ug)
Relatively high (1 ug)
Low degree
High degree
ENZYMATIC ACTIVITY
No
Usually
PROGENICITY
Yes
Occasionally
RELATIONSHIP TO CELL DENATURED BY BOILING ANTIGENIC FORM TOXOID POTENCY SPECIFICITY
OR
EXOTOXINS
ENDOTOXIN
Proteins Heat labile
Lipopolysaccharides Heat stable
Actively secreted by cells; diffuse into surrounding medium
Form part of cell wall; do not diffuse into surrounding medium
Readily separable from cultures by physical means such as filtration Action often enzymic Specific pharmacological effect for each exotoxin Specific tissue affinities Active in very minute dose Highly antigenic
Obtained only by cell lysis
No enzymic action Effect non-specific; action common to all endotoxins No specific tissue affinity Active only in very large dose Weakly antigenic
Action specifically neutralized by antibody
Neutralization by antibody ineffective
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6. What differences are between Innate and Adaptive Immunity? INNATE IMMUNITY ADAPTIVE IMMUNITY Antigen Independent ANTIGEN DEPENDENT No time lag A LAG PERIOD Not antigen specific ANTIGEN SPECIFIC No immunologic memory DEVELOPMENT OF MEMORY
7.What kinds of Generalized infection are? TOXEMIA :: : is the presence of exotoxins in the blood where there are no bacteria. ENDOTOXEMIA :: is the presence of endotoxins in the blood. BACTEREMIA :: is an invasion of the bloodstream by bacteria,not reproduction in bloodstream. SEPTICEMIA :: illness that occurs when poisonous substances (toxins) produced by certain bacteria enter the bloodstream PYEMIA :: is caused by pyogenic microorganisms in the blood.
LOCAL INFECTION
APPARENT INFECTION
GENERALIZED OR SYSTEMIC INFECTION
Toxemia Endotoxemia Bacteremia Septicemia Pyemia
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14. Coccus
REFERENCE
STAPHYLOCOCCUS
Section 1
Name :: Staphylococcus aureus Disease caused ::
FOOD POSOINING
Abscesses of many organs, endocarditis, osteomyelitis, septic arthritis,and impetigo.
Also hospital-acquired pneumonia, surgical wound infections, and sepsis. Also exotoxin-mediated diseases such as gastroenteritis (food poisoning), toxic shock syndrome, and scalded skin syndrome.
It is one of the most common causes of human infections.
Atopic Dermatitis
Type :: GRAM + POSITIVE(Coagulase-positive. Catalasepositive. Most isolates produce β-lactamase.) (young cocci strongly shows Gram+ ; on aging it becomes Gram-) Appearance :: spherical Arrangement :: Cluster. GRAPE-LIKE IRREGULAR CLUSTERS (single coccus, pairs, tetrads, chain) Growth :: rapidly in 37◦C but pigment best at room temperature (20-25◦C)
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Habitat :: THE HUMAN NOSE; found on Human Skin Special characteristics :: Colonies
On solid media ; Round, Smooth, Raised, Glistening
Forms gray to deep golden yellow colonies
Exceptional case::
Peptostreptococcus species, which are anaerobic cocci, often resemble staphylococci in morphology. The staphylococci produce catalase, which differentiates them from the streptococci
Transmission :: Via Hands Pathogenesis and Symptomatology :: A. Pathogenic Substances 1. Coagulase and Clumping Factor 2. Exotoxins (1) Leukocidins (2) Exfoliative Toxins (3) Toxic Shock Syndrome Toxin (4) Enterotoxins B. Clinical Findings 1. Invasive and Pyogenic Infection 2. Toxin-Mediated diseases (1) Scalded Skin Syndrome (2) Toxic Shock Syndrome 3. Staphylococcal Food Poisoning Pathogenesis ::
Abscess containing pus is the most common lesion.
Three exotoxins are also made.
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Toxic shock syndrome toxin is a superantigen and causes toxic shock syndrome by stimulating many helper T cells to release large amounts of lymphokines, especially IL-2. Enterotoxin, which causes food poisoning, is also a superantigen.
Food poisoning has a short incubation period because it is preformed in food. Scalded skin syndrome toxin is a protease that cleaves desmoglein in tight junctions in the skin.
Protein A is an important virulence factor because it binds to the heavy chain of IgG and prevents the activation of complement.
Predisposing factors to infection include breaks in the skin, foreign bodies such as sutures, neutrophil levels below 500/μL, intravenous drug use (predisposes to right-sided endocarditis), and tampon use (predisposes to toxic shock syndrome).
STAPHYLOCOCCAL DISEASE
Skin and soft tissue :: Folliculitis, furuncle (boil), abscess (particularly breast abscess), wound infection, carbuncle[cluster of boils draining puss into the cell], impetigo, paronychia[nail disease], less often cellulitis[infection in the inner layer of the skin].
Musculoskeletal :: Osteomyelitis[infection and imflammation of bone and bone marrow], arthritis, burstitis[imflamation of bursa], pyomyositis[acute bacterial infection on skeletal muscles]
Respiratory :: Tonsillitis, pharyngitits, sinusitis, otitis [inflammation of ears], bronchopneumonia[lung inflammation], lung abcess[collection of puss in the lung], empyema[pleural effusion containing pus], rarely pneumonia
Central nervous system :: Abscess, meningitis, intracranial thrombophlebitis
Endovascular :: Bacteremia, septicemia, pyemia, endocarditis
Urinary :: Staphylococci are uncommon in routine urinary tract infection, though they do cause infection in local instrumentation, implants or diabetes. Bacteremia may occur when there is low colony counts in urinary isolates of staphylococci.
Laboratory diagnosis ::
Gram-stained smear and culture. Yellow or gold colonies on blood agar; colonies often βhemolytic.
Staphylococcus aureus is coagulase positive;
Staphylococcus epidermidis is coagulase-negative.
Serologic tests not useful.
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Identification:: Staphylococci grow overnight on blood agar incubated aerobically. Catalase and coagulase test perform directly from the colonies.
Antibiotic susceptibility tests are indicated because of the emerging resistance of S.aureus to multiple antimicrobics, particularly METHICILLIN and VANCOMYCIN.
Blood cultures are usually positive in conditions such as acute staphylococcal arthritis, osteomyelitis and endocarditis but less often in localized infection such as deep abscesses.
Treatment ::
Penicillin G for sensitive isolates; β-lactamase–resistant penicillins such as nafcillin for resistant isolates; vancomycin for isolates resistant to nafcillin.
About 85% are resistant to penicillin G. Plasmid-encoded β-lactamase mediates most resistance.
Resistance to nafcillin is caused by changes in binding proteins.
Some isolates are tolerant to penicillin. Rare vancomycin-resistant strains have emerged.
Prevention ::
Cefazolin is used to prevent surgical wound infections. No vaccine is available.
Handwashing reduces spread.
Name :: Staphylococcus epidermidis Disease caused :: Endocarditis on prosthetic heart valves, prosthetic hip infection, intravascular catheter infection, cerebrospinal fluid shunt infection, neonatal sepsis. Type :: GRAM + POSITIVE(Coagulase-> negative-; Catalase-> positive+) Appearance :: Spherical Arrangement :: Clusters. Habitat :: Normal flora of the human skin and mucous membranes. Transmission :: Its probably the patient’s own strains that cause infection, but transmission from person to person via hands may occur
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Pathogenesis ::
Glycocalyx-producing strains adhere well to foreign bodies such as prosthetic implants and catheters.
It is a low-virulence organism that causes disease primarily in immunocompromised patients and in those with implants.
It is a major cause of hospital-acquired infections.
Unlike S. aureus, no exotoxins have been identified.
Laboratory diagnosis ::
Gram-stained smear and culture. Whitish, nonhemolytic colonies on blood agar. It is coagulase-negative.
S. epidermidis is sensitive to novobiocin, whereas the other coagulase-negative staphylococcus Staphylococcus saprophyticus, is resistant.
Serologic tests are not useful.
Treatment :: Vancomycin plus either rifampin or an aminoglycoside. It produces β- lactamases and is resistant to many antibiotics. Prevention :: There is no drug or vaccine.
STREPTOCOCCUS PNEUMONIAE
Section 3
Name :: Streptococcus pneumoniae (Pneumococcus) Disease caused :: The most common diseases are •
pneumonia
•
meningitis in adults
•
otitis media and sinusitis in children.
Type :: GRAM +positive (Calatase-> negative-) Appearance :: Lancet shaped Arrangement :: Cocci in pairs (diplococci) or short chains Habitat :: HUMAN UPPER RESPIRATORY TRACT Special characteristics :: Growth is inhibited by optochin in contrast to viridans streptococci, which are resistant. Colonies are bilesoluble. Prominent polysaccharide capsule. Eighty-five
PAGE 32
serotypes based on antigenicity of polysaccharide capsule. [One of the three classical encapsulated pyogenic bacteria (Neisseria meningitidis and Haemophilus influenzae are the other two).]
Transmission :: Via Respiratory droplets. Pathogenesis :: •
Induces inflammatory response. No known exotoxins.
•
Polysaccharide capsule retards phagocytosis. Antipolysaccharide antibody opsonizes the organism and provides type-specific immunity.
•
IgA protease degrades secretory IgA on respiratory mucosa, allowing colonization.
•
Viral respiratory infection predisposes to pneumococcal pneumonia by damaging mucociliary elevator; splenectomy predisposes to sepsis.
•
Skull fracture with spinal fluid leakage from nose predisposes to meningitis.
Laboratory diagnosis :: •
Gram-stained smear and culture. α-Hemolytic colonies on blood agar.
•
Growth inhibited by bile and optochin. Quellung reaction occurs (swelling of capsule with type-specific antiserum).
•
Serologic tests for antibody not useful. Tests for capsular antigen in spinal fluid and C polysaccharide in urine can be diagnostic.
Treatment :: •
Penicillin G. Low-level and high-level resistance to penicillin is caused by alterations in penicillin-binding proteins.
•
No β-lactamase is made.
Prevention :: •
Two vaccines are available. o The one used in adults contains capsular polysaccharide of the 23 serotypes that cause bacteremia most frequently. o The other, which is used primarily in children under the age of 2 years, contains capsular polysaccharide of 13 serotypes coupled to carrier protein (diphtheria toxoid).
•
Oral penicillin is used in immunocompromised children.
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REVIEW QUESTIONS TERMS 1. SPA > staphylococcus protein A (SPA) > A surface protein of S.aureus. > SPA binds Fc portion of IgG molecules nonspecifically . The Fab portion of IgG bound to protein A is free to combine with a specific antigen
2. COAGULASE Staphylococcus only show coagulase reaction. So it gives coagulase test. BOUND COAGULASE FREE COAGULASE Bound coagulase fibrinogen Clump of the bacterial
fibrin
Free coagulase coagulase-reacting factor
thrombinlike factor fibrinogen
fibrin
Achieve the same purpose This factor catalyzes the conversion of fibrinogen to insoluble fibrin. 3. WHAT ARE THE BIOLOGICAL EFFECTS OF SPA ? Binds to the Fc portion of IgG at the complement-binding site Prevent the activation of complement 4.WHAT IS THE PRINCIPLE OF COAGGLUTINATION TEST. Protein A with attached IgG molecules directed against a specific antigen will agglutinate the bacteria that have the antigen. 5. WHAT ARE THE VIRULENCE FACTORS PRODUCED BY S.AUREUS. The Virulence factors produced by S. aureus are :: i. STRUCTURAL COMPONENTS ii. INVASIVE ENZYME iii. TOXIN
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Staphylococci cause diseases both through their ability to multiply ang spread widely in tissues and through the virulence factors 6 WRITE THE DISEASE CAUSED BY S.AUREUS The clinical manifestation of S.aureus can be divided into two forms :: INVASIVE DISEASE abscess formation Localized infections: skin infections, pneumonia, empyema, etc. S. aureus disseminates (bacteremia ensues): endocarditis, acute hematogenous osteomyelitis, septic arthritis, meningitis, or pulmonary infections occur. TOXIGENIC DISEASE They are caused by the extracellular toxins produced by S.aureus They involve a variety of syndromes STAPHYLOCOCCAL FOOD POISONING • The result of ingestion of enterotoxin • Most patients are fully recovered in 24 to 48 hours (Self-limited disease ). STAPHYLOCOCCAL ENTEROCOLITIS • Imbalance of the normal flora • The abuse of oral antibiotics STAPHYLOCOCCAL SCALDED SKIN SYNDROME • Infants and young children • Communicable TOXIC SHOCK SYNDROME (TSS) • It’s a multisystem, febrile illness • Start abruptly and include fever, hypotension, vomiting, diarrhea. 7. HOW TO SELECTIVELY ISOLATE AND DIFFERENTIATE S. AUREUS FROM CLINICAL SPECIMENS? SPECIMENT pus (localized skin infection) sputum (low respiratory tract infection) blood (septic shock, osteomyelitis, endocarditis) food/feces or vomit (food poisoning) LABORATORY DIAGNOSIS
directly smear for gram stain isolation and identification: blood agar coagulase test enterotoxin test and animal test mannitol fermentation
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ITS DIFFERENTIATED FROM MANNITOL FERMENTATION If there is a mixture of organisms in the specimen, S. aureus can be selectively isolated on mannitol salt agar (MSA), which is supplemented with 7.5 % sodium chloride inhibiting the growth of most other organisms, and mannitol fermented by S. aureus but not most other staphylococci.
Selective medium
8. WRITE THE CHARACTERISTICS OF SKIN INFECTIONS CAUSED BY S. AUREUS AND STREPTOCOCCI PYOGENES? EXPLAIN WHY. S. AUREUS Example :: Folliculitis and Furuncles (Boils) Skin infections caused by S. aureus are usually localized. The focus of infection has clear boundaries with the surrounding tissue; feel hard Pus is thick, sticky, and yellow. S. PYOGENES Pyogenic diseases are those in which pus is formed. Such as pharyngitis, impetigo and cellulitis. Pharyngitis Impetigo Cellulitis Skin infections caused by Streptococcus pyogenes are usually diffused. The focus of infection has no clear boundaries with the surrounding tissue; feel soft pus is thin, watery, and bloody . 9. Write five differential characteristics of S. aureus > Usually produces GOLDEN YELLOW PIGMENT > On blood agar, colonies are usually surrounded by a zone of complete hemolysis (βhemolysis) > Staphylococci are salt-tolerate and can be isolated from materials such as feces in media containing 7-10 % sodium chloride (Selective medium). > Staphylococci catalase (+) catalyze the formation of oxygen and water of hydrogen peroxide > Carbohydrates; lactic acid + > S aureus mannitol (differential characteristics)
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10. Write classification of the streptococci according to two different criterions. The two criterion are :: Hemolysis o α (alpha) - partial hemolysis - green color o β (beta) - complete clearing o γ (gamma) - no lysis Group-specific substance o They placed them into serological groups A-H and K-V on the basis of C substance. o More than 90% of streptococcal disease in humans is caused by group A bhemolytic streptococci such as S.pyogenes. 11. Write the differences between hemolysin O and hemolysin S produced by Group A streptococcus. Group A streptococcus liberates two kinds of hemolysins streptolysins O (SLO); streptolysins S (SLS). STREPTOLYSIN O (SLO)
STREPTOLYSIN S (SLS)
Oxygen Labile
Oxygen Stable
Hemolytically active - - - - inactived
Hemolytically active
Lyse animal erythrocytes and leukocytes in-vovo A factor in the pathogenesis of rheumatic fever.
Accounts for zone of βhemolysis
Immunogenic - - - - ASO (anti-streptolysin O)
Non-immunogenic
12. Write the diseases caused by Streptococcus pyogenes. Streptococcal disease is divided into three categories: ①pyogenic diseases such as pharyngitis and cellulitis, ②toxigenic diseases such as scarlet fever and toxic shock syndrome. ③immunological diseases such as rheumatic fever and acute glomerulonephritis. Pyogenic diseases are those in which pus is formed. Such as pharyngitis, impetigo and cellulitis. Pharyngitis Impetigo Cellulitis
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13. Write the names of invasive enzymes produced by Streptococci and their effects. Hyaluronidase (spreading factor): Splits hyaluronic acids bacteria spread Streptokinase (SK): Lyse fibrin, prevent plasma clotting bacteria spread Streptodornase (SD): Resolve DNA bacteria spread 14. What virulence factors produced by Streptococci. pyogenes facilitate spread of the organisms
15. How to differentiate Streptococcus pneumoniae from a-haemolytic streptococci Once cultured, the pneumococci can be differentiated from a-hemolytic streptococci by the following tests: OPTOCHIN SUSCEPTIBILITY TEST Optochin is an antimicrobial drug derived from quinine. When disks containing the drug are placed on blood agar previously seeded with pneumococci, zones of inhibition can be observed around the optochin. BILE SOLUBILITY TEST. The pneumococci produce an enzyme that cleaves specific covalent bonds in the peptidoglycan layer. This enzyme is activated by bile or bile salts. When a few drops of bile salts are added to a broth culture of pneumococci, the cells are rapidly lysed. ABILITY TO FERMENT INULIN OR
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Hemolysis
Optochin sensitivity
Bile solubility
Inulin Fermentation
S. pneumoniae
Sensitive (≥ 14 mm)
Soluble
Not ferment
Viridans strep
Resistant
Insoluble
Ferment
(≤13 mm)
NEISSERIA NEISSERIA GONORRHOEAE Name :: Neisseria gonorrhoeae (Gonococcus) Disease caused :: GONORRHEA, neonatal conjunctivitis and pelvic inflammatory disease. Type :: GRAM –negative (oxidase-> positive+ ) Appearance :: spherical Arrangement :: “kidney-bean” diplococci Habitat :: THE HUMAN GENITAL TRACT Special characteristics :: Insignificant capsule Transmission :: •
In adults by sexual contact
•
Transmission to neonates during birth
Pathogenesis :: •
Organism invades mucous membranes and causes inflammation.
•
Endotoxin present but weaker than that of meningococcus, so less severe disease when bacteremia occurs.
•
No exotoxins identified.
•
IgA protease and pili are virulence factors.
Laboratory diagnosis :: •
Gram-stained smear and culture.
•
Organism visible intracellularly within neutrophils in urethral exudate.
•
Oxidase-positive colonies on Thayer-Martin medium.
•
Gonococci do not ferment maltose, whereas meningococci do.
•
Serologic tests not useful. Nucleic acid amplification tests (NAAT) are used as a screening test in urogenital infections.
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Treatment :: •
Ceftriaxone for uncomplicated cases.
•
Azithromycin or doxycycline added for urethritis caused by Chlamydia trachomatis.
•
High-level resistance to penicillin is caused by plasmid-encoded penicillinase.
•
Low-level resistance to penicillin is caused by reduced permeability and altered binding proteins.
Prevention :: •
No drug or vaccine.
•
Condoms offer protection.
•
Trace contacts and treat to interrupt transmission.
•
Treat eyes of newborns with erythromycin ointment or silver nitrate to prevent conjunctivitis.
NEISSERIA MENINGITIDIS Name :: Neisseria meningitides (Meningococcus) Disease caused :: MENINGITIS and MENINGOCOCCEMIA Type :: GRAM –negative (Oxidase-> positive+) Appearance :: kidney bean Arrangement :: diplococci Habitat :: THE HUMAN UPPER RESPIRATORY TRACT Special characteristics :: Large polysaccharide capsule. One of the three classic encapsulated pyogenic bacteria (Streptococcus pneumoniae and Haemophilus influenzae are the other two). Transmission :: Via Respiratory droplets. Pathogenesis :: •
After colonizing the upper respiratory tract, the organism reaches the meninges via the bloodstream.
•
Endotoxin in cell wall causes symptoms of septic shock seen in meningococcemia.
•
No known exotoxins; IgA protease produced.
•
Capsule is antiphagocytic.
•
Deficiency in late complement components predisposes to recurrent meningococcal infections.
Laboratory diagnosis ::
PAGE 40
•
Gram-stained smear and culture. Oxidase-positive colonies on chocolate agar.
•
Ferments maltose in contrast to gonococci, which do not.
•
Serologic tests not useful.
Treatment ::
Penicillin G (no significant resistance)
Prevention :: •
Vaccine contains capsular polysaccharide of strains A, C, Y, and W-135.
•
One form of the vaccine contains the polysaccharides coupled to a carrier protein (diphtheria toxoid), and one contains only the polysaccharides.
•
Rifampin or ciprofloxacin given to close contacts to decrease oropharyngeal carriage.
REVIEW QUESTIONS 1. Write the virulence factors produced by N. gonorrhoeae and how to prevent ophthalmia neonatorum. The virulence factor of N.gonorrhoeae are :: Pili o The process of infection of gonococci: o Gonococci attach to mucosal cells, penetrate into the cells and multiply, and then pass through the cells into the subepithelial space, where infection is established. Outer membrane proteins (OMP) o They are believed to protect the phagocytosed bacteria from intracellular killing by inhibiting phagolysosome fusion. IgA protease o It splits and inactivates sIgA. PREVENTION OF OPTHALMIA NEONATORUM o Ocular infections occur most commonly in newborns who are exposed to infected secretions in the birth canal. o It may be prevented in areas of high prevalence by the instillation of 1% aqueous sliver nitrate in the eyes of newborn babies. 2. Write the virulence factors produced by N.meningitidis and why the child are susceptible to N.meningitidis infection. PATHOGENICITY Human is the only natural host for pathogenic meningococci. Child: susceptible; adult: through inapparent infections
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VIRULENCE FACTORS: *PILI–attach to nasopharyngeal mucosa o Experiments with nasopharyngeal tissue cultures have shown that meningococci attach selectively to specific receptors on nonciliated columnar cells of the nasopharynx with the aid of pili. Meningococci without pili are less able to attach to these cells. *CAPSULE–antiphagocytosis o Polysaccharide capsule: the antiphagocytic properties of polysaccharide capsule enable N. meningitidis to resist phagocytosis. *ENDOTOXIN–main pathogenic substance o is present in the outer membrane, is also responsible for many of the toxic effects such as fever, shock, and other pathophysiologic changes. *IgA PROTEASE- cleave secretory IgA o can cleave secretory IgA and help the bacteria to attach to the membranes of the upper respiratory tract. THE CHILD ARE SUSCEPTIBLE TO N.MENINGITIDIS INFECTION. o DUE TO LACK OF SPECIFIC ANTI-BODIES o It carries a high mortality rate if untreated but is a vaccine-preventable disease. o Children 2–10 years of age who are at high risk for meningococcal disease such as certain chronic medical conditions and travel to or reside in countries with hyperendemic or epidemic meningococcal disease should receive primary immunization. o Although safety and efficacy of the vaccine have not been established in children younger than 2 years of age and under outbreak control, the unconjugated vaccine can be considered.
3. How to collect the clinical specimens of patients suspected of gonorrheal infection. o SPECIMEN: purulent secretion of genitourinary tract. o ISOLATION AND IDENTIFICATION: direct smear, gram stain,and culture, as well as biochemical tests. o The finding of intracellular G- diplococci in smears of urethral pus by light microscopy is viewed as presumptive evidence of gonorrheal infection in men. OR Specimens collected: A) In men: a) Acute infection- Urethral discharge b) Chronic infectioni) Morning drop PAGE 42
ii) Discharge collected after prostatic massage iii) Centrifuged deposit of urine B) In women: i) Urethral discharge ii) Cervical swabs C) In both the sexes: Blood, CSF, synovial fluid, throat swab, rectal swab & material from skin rashes. Transport: If there is delay in processing than the specimens should be sent in “ Stuart’s medium”.
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15. Enteric Bacilli REFERENCE ESCHERICHIA Name :: Escherichia coli Disease caused :: URINARY TRACT INFECTION (UTI), SEPSIS, NEONATAL MENINGITIS, AND “TRAVELER’S DIARRHEA” Type :: facultative GRAM – negative rods Habitat :: THE HUMAN COLON Special characteristics :: Ferment lactose Transmission :: •
It colonizes the vagina and urethra. From the urethra, it ascends and causes UTI.
•
Acquired during birth in neonatal meningitis and by the fecal–oral route in diarrhea.
Pathogenesis :: • Endotoxin in cell wall causes septic shock. • Two enterotoxins are produced by enterotoxigenic E.coli (ETEC) strains. • The heat-labile toxin (LT) stimulates adenylate cyclase by ADP-ribosylation. • Increased cyclic AMP causes outflow of chloride ions and water, resulting in diarrhea. • The heat-stable toxin (ST) causes diarrhea, perhaps by stimulating guanylate cyclase. • Virulence factors include pili for attachment to mucosal surfaces and a capsule that impedes phagocytosis. • Shiga toxin (verotoxin) is an enterotoxin produced by E. coli strains (STEC) with the O157:H7 serotype. • It causes bloody diarrhea and hemolytic-uremic syndrome associated with eating undercooked meat. • Shiga toxin (verotoxin) inhibits protein synthesis by removing adenine from the 28S rRNA of human ribosomes.
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• Predisposing factors to UTI in women include the proximity of the anus to the vagina and urethra, as well as a short urethra. This leads to colonization of the urethra and vagina by the fecal flora. • Abnormalities (e.g., strictures, valves, and stones) predispose as well. • Indwelling urinary catheters and intravenous lines predispose to UTI and sepsis, respectively. • Colonization of the vagina leads to neonatal meningitis acquired during birth. • The main virulence factor for neonatal meningitis is the K1 capsular polysaccharide. Laboratory diagnosis :: •
Gram-stained smear and culture. Lactose-fermenting colonies on eosin–methylene blue (EMB) or MacConkey’s agar.
•
Green sheen on EMB agar.
•
Triple sugar iron (TSI) agar shows acid slant and acid butt with gas but no H2S.
•
Differentiate from other lactose-positive organisms by biochemical reactions.
•
For epidemiologic studies, type organism by O and H antigens by using known antisera.
•
Serologic tests for antibodies in patient’s serum not useful.
Treatment :: •
Ampicillin or sulfonamides for UTIs. Third-generation cephalosporins for meningitis and sepsis. Rehydration is effective in traveler’s diarrhea; trimethoprim-sulfamethoxazole may shorten duration of symptoms.
•
Antibiotic resistance mediated by plasmid-encoded enzymes (e.g., β-lactamase and aminoglycoside-modifying enzymes).
Prevention :: •
Prevention of UTI involves limiting the frequency and duration of urinary catheterization.
•
Prevention of sepsis involves promptly removing or switching sites of intravenous lines.
•
Traveler’s diarrhea is prevented by eating only cooked food and drinking boiled water in certain countries.
•
Prophylactic doxycycline or Pepto-Bismol may prevent traveler’s diarrhea.
•
There is no vaccine that prevents any of the diseases caused by E. coli.
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SHIGELLA Name :: Shigella species (eg: Shigella dysenteriae, Shigella sonnei) Disease caused :: ENTROCOLTIS (Dysentery) Type :: facultative GRAM –negative rod Habitat :: THE HUMAN COLON; unlike Salmonella enterica, there are no animal carriers for Shigella Special characteristics :: Non-lactose fermenting. Nonmotile, in contrast to Salmonella. Transmission :: by Fecal-oral route Pathogenesis :: • Invades the mucosa of the ileum and colon but does not penetrate farther; therefore, sepsis is rare. • Endotoxin in cell wall. • Infectious dose is much lower (1–10 organisms) than that of Salmonella. The infectious dose of Shigella is low because it is resistant to stomach acid. • Children in mental institutions and day care centers experience outbreaks of shigellosis. • No chronic carrier state. Laboratory diagnosis :: • Gram-stained smear and culture. Non–lactose-fermenting colonies on EMB or MacConkey’s agar. TSI agar shows an alkaline slant with an acid butt and no gas or H2S. • Identified by biochemical reactions or by serology with anti-O antibody in agglutination test. • Serologic tests for antibodies in the patient’s serum are not done. Treatment :: • In most cases, fluid and electrolyte replacement only. In severe cases, ciprofloxacin. • Resistance is mediated by plasmid-encoded enzymes (e.g., β-lactamase, which degrades ampicillin, and a mutant pteroate synthetase, which reduces sensitivity to sulfonamides). Prevention :: • Public health measures (e.g., sewage disposal, chlorination of the water supply, stool cultures for food handlers, and handwashing prior to food handling). • Prophylactic drugs not used. No vaccine is available.
SALMONELLA TYPHI Name :: Salmonella typhi Disease caused :: TYPHOID FEVER Type :: facultative GRAM – negative rods. Habitat :: THE HUMAN COLON, in contrast to other salmonellae which are found in colon of animals as well.
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Special characteristics :: Non lactose fermenting. Produces H2S Transmission :: By Fecal-oral route Pathogenesis :: • Infects the cells of the reticuloendothelial system, especially in the liver and spleen. • Endotoxin in cell wall causes fever. • Capsule (Vi antigen) is a virulence factor. • No exotoxins known. • Decreased stomach acid resulting from ingestion of antacids or gastrectomy predisposes to Salmonella infections. • Chronic carrier state established in gallbladder. • Organism excreted in bile results in fecal– oral spread to others. Laboratory diagnosis :: • Gram-stained smear and culture. • Non–lactose-fermenting colonies on EMB or MacConkey’s agar. • TSI agar shows alkaline slant and acid butt, with no gas and a small amount of H2S. • Biochemical and serologic reactions used to identify species. • Identity can be determined by using known antisera against O, H, and Vi antigens in agglutination test. • WIDAL TEST detects agglutinating antibodies to O and H antigens in patient’s serum, but its use is limited. Treatment :: • Most effective drug is ceftriaxone. • Ampicillin and trimethoprimsulfamethoxazole can be used in patients who are not severely ill. • Resistance to chloramphenicol and ampicillin is mediated by plasmid-encoded acetylating enzymes and β-lactamase, respectively. Prevention :: • Public health measures (e.g., sewage disposal, chlorination of the water supply, stool cultures for food handlers, and handwashing prior to food handling). • Two vaccines are in common use; one vaccine contains purified Vi polysaccharide capsule as the immunogen and the other contains live, attenuated S. typhi as the immunogen.
o Clinical disease induced by salmonellae Enteric fever
Septicemias
Gastroenterocolitis
7 – 20 days
Variable
8 – 48 hours
Onset
Insidious
Abrupt
Abrupt
Fever
Gradual, then high plateau, with “typhoidal” state
Rapid rise, then spiking “septic” temperature
Usually low
Incubation period
PAGE 47
Duration of disease
Several weeks
Variable
2 – 5 days
Gastrointestinal symptoms
Often early constipation; later, bloody diarrhea
Often none
Nausea, vomiting, diarrhea at onset
Blood cultures
Positive in first to second weeks of disease
Positive during high fever
Negative
Stool cultures
Positive from 2nd week on; negative earlier in disease
Infrequently positive
Positive soon after onset
KLEBSIELLA AND PROTEUS KLEBSIELLA Name :: Klebsiella pneumoniae Disease caused :: PNEUMONIA, UTI and SEPSIS Type :: facultative GRAM – negative rods with large polysaccharide capsule. Habitat :: HUMAN UPPER RESPIRATORY and ENTERIC TRACTS Transmission :: Organism is transmitted to the lungs by aspiration from upper respiratory tract and by inhalation of respiratory droplets. It is transmitted to the urinary tract by ascending spread of fecal flora. Pathogenesis :: Endotoxin causes fever and shock associated with sepsis. No exotoxin known. Organism has large capsule, which impedes phagocytosis. Chronic pulmonary disease predisposes to pneumonia; catheterization predisposes to UTI. Laboratory diagnosis :: Gram-stained smear and culture. Characteristic mucoid colonies are a consequence of the organism’s abundant polysaccharide capsule. Lactose-fermenting colonies on MacConkey’s agar. Differentiated from Enterobacter and Serratia by biochemical reactions. Treatment :: Cephalosporins alone or with aminoglycosides, but antibiotic sensitivity testing must be done. Resistance is mediated by plasmid-encoded enzymes, especially β-lactamase. Prevention :: No vaccine or drug is available. Urinary and intravenous catheters should be removed promptly
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PROTEUS Name :: Proteus species (e.g., Proteus vulgaris, Proteus mirabilis) Disease caused :: UTI and sepsis. Type :: facultative GRAM – negative rods. Habitat :: THE HUMAN COLON and the environment (soil and water) Special characteristics :: Non–lactose-fermenting. Highly motile. Produce urease, as do Morganella and Providencia species.Antigens of OX strains of P. vulgaris cross-react with many rickettsiae. Transmission :: Transmission to urinary tract is by ascending spread of fecal flora.
Pathogenesis :: Endotoxin causes fever and shock associated with sepsis. No exotoxins known. Urease is a virulence factor because it degrades urea to produce ammonia, which raises the pH. This leads to “struvite” stones, which can obstruct urine flow, damage urinary epithelium, and serve as a nidus for recurrent infection by trapping bacteria within the stone. Organism is highly motile, which may facilitate entry into the bladder. Predisposing factors are colonization of the vagina, urinary catheters, and abnormalities of the urinary tract such as strictures, valves, and stones. Laboratory diagnosis :: Gram-stained smear and culture. “Swarming” (spreading) effect over blood agar plate as a consequence of the organism’s active motility. Non–lactose-fermenting colonies on EMB or MacConkey’s agar. TSI agar shows an alkaline slant and acid butt with H2S. Organism produces urease, whereas Salmonella, which can appear similar on TSI agar, does not. Serologic tests not useful. P. mirabilis is indole-negative, whereas P. vulgaris, M. morganii, and Providencia species are indole-positive Treatment :: Trimethoprim-sulfamethoxazole or ampicillin is often used for uncomplicated UTIs, but a third-generation cephalosporin should be used for serious infections. The indole-negative species P. mirabilis is more likely to be sensitive to antibiotics such as ampicillin than are the indole-positive species.
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Antibiotic sensitivities should be tested. Resistance is mediated by plasmid-encoded enzymes. Prevention :: No vaccine or drug is available. Prompt removal of urinary catheters helps prevent UTIs.
REVIEW QUESTIONS TERMS 1. WIDAL TEST > A tube test for determining the quantity of agglutinating antibodies in the serum of a patient suspected of typhoid fever. > Direct diagnosis: stain, isolation and culture. Ag, DNA > Indirect diagnosis: Ab OR > It is a presumptive serological test forenteric fever or undulant fever whereby bacteria causing typhoid fever are mixed with a serum containing specific antibodies obtained from an infected individual. > In cases of Salmonella infection, it is a demonstration of the presence of O-soma falsepositive result. 2. SHIGA TOXIN o Accordingly to the virulence factor of Shigella, Shiga toxin is exotoxin. o Subunit A, subunit B. The toxin inhibits protein synthesis. o Neurotoxic, enterotoxic OR o Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, expressed by genes considered to be part of the genome of lambdoid prophages. o The toxins are named for Kiyoshi Shiga, who first described the bacterial origin of dysentery caused by Shigella dysenteriae. o The most common sources for Shiga toxin are the bacteria S. dysenteriae and the shigatoxigenic group of Escherichia coli(STEC) 3. WRITE FIVE CLASSES OF E.COLI THAT CAUSE GASTROENTERITIS AND THEIR PATHOGENESIS. Some strains of E.coli cause diarrhea i. ENTEROTOXIGENIC E. coli (ETEC), is associated with travellers diarrhea and diarrhea in children in developing countries. Transmission is via contaminated food or water. This disease is caused by LT, ST.
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ii. • •
ENTEROINVASIVE E. coli (EIEC), also called as Shigella-like E coli strains. There will be dysentery-like diarrhea in elder children and adult include fever,severe abdominal cramps, malaise, and watery diarrhea followed by scanty stools containing blood, mucus, and pus.
iii. • • • • •
iv.
ENTEROHEMORRHAGIC E. coli (EHEC), produces verotoxin moderately invasive O157:H7 Diarrhea; hemorrhagic colitis; hemolytic uremic syndrome [HUS]. Clinical manifestation includes :: copious(വളരെയേരെ) bloody discharge, intense inflammatory response, pediatric diarrhea (caused by this strain can be fatal due to acute kidney failure) ENTEROPATHOGENIC E. coli (EPEC),
• Does not produce LT or ST; Moderately invasive • BUNDLE-FORMING PILI are involved in attachment to the intestinal mucosa and destruction of the microvilli • Symptom includes: malaise and low grade fever, diarrhea, vomiting, nausea, non- bloody stools v.
ENTEROAGGREGATIVE E. coli (EAggEC).
• The organisms are characterized by their distinct pattern of adherence to human cells. • Produce Enteroaggregative heat-stable toxin (EAST) • Symptoms include watery diarrhea, vomiting, and occasional abdominal pain. OR Name
Host
Description
Enterotoxigenic E.coli (ETEC)
Causative agent of diarrhea Uses fimbrial adhesions to bind (without fever) in human enterocyte cells in small intestine.
Enteropathogenic E.coli (EPEC)
Causative agent of diarrhea Lack fimbriae, ST and LT toxins but in humans they use an adhesion known as initimin to bind host intestinal cells.
Enteroinvasive E.coli (EIEC)
Found only in humans
Infection causes a syndrome that is identical to shigellosis, with profuse diarrhea and high fever
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Enterohemorrhagic E.coli (EHEC)
Found in humans
Causes bloody diarrhea and no fever. Also hemolytic-uremic syndrome and sudden kidney failure.
Enteroaggregative E.coli (EAEC)
Found only in humans
EAEC bind to the intestinal mucosa to cause watery diarrhea without fever.
4. DESCRIBE THE CLINICAL MANIFESTATIONS OF SHIGELLOSIS AND THE VIRULENCE FACTORS PRODUCED BY SHIGELLA. (Shigellosis, also known as bacillary dysentery or Marlow Syndrome, in its most severe manifestation, is a foodborne illness caused by infection by bacteria of the genus Shigella.) CLINICAL SIGNIFICANCE • bloody feces, intestinal pain, pus • Fecal-oral route causes Dehydration, Vomiting, Diarrhea, Dysenetry, Tenesmus, Colitis • The infective dose required to cause infection is very low. • Incubation period; symptoms of bacterial dysentery • The severity of the disease depends upon the species one is infected with. S. dysenteria is the most pathogenic followed by S. flexneri, S. boydii and S. sonnei. VIRULENCE FACTORS 1. INVASIVENESS (E.coli) o Within 2-3 days o Epithelial cell damage
Shigella attachment & penetration
2. ENDOTOXIN o This endotoxin damages the mucous of large intestine and terminal ileum o makes microabscessses in the wall and leads to necrosis of the mucous membrane, superficial ulceration, bleeding, and formation of abundant pus and blood in the stool. o The endotoxin contribute to the irritation of the intestine wall and the cause of abdominal cramps and tenesmus. 3. EXOTOXIN (Shiga toxin) o Subunit A, subunit B o The toxin inhibits protein synthesis. o Neurotoxic, enterotoxic
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5. DESCRIBE THE CLINICAL MANIFESTATION OF SALMONELLA INFECTION AND THE VIRULENCE FACTORS PRODUCED BY SALMONELLA. CLINICAL MANIFESTATION 1) Gastroenteritis --- food poisoning (enterotoxin) • • •
It is the most common manifestation of salmonella infection. Except for diarrhea, nausea, vomiting, abdominal cramps, headache, fever (38oC to 39oC) and chills are common. The duration of fever and diarrhea is usually 2 to 7 days.
2) Septicemia •
More common in children and immunocompromised people.
3) Enteric fevers ---- typhoid • •
S. typhi produce a febrile illness called typhoid fever. A mild form of this disease: paratyphoid fever.
Symptoms of enteric fevers are nonspecific VIRULENCE FACTORS PRODUCED BY SALMONELLA • The ability to invade and replicate in the cells • Endotoxin (LPS) • Exotoxin---Some species of Salmonella produce exotoxins which like ETEC's. 6. HOW TO COLLECT THE CLINICAL SPECIMENS OF PATIENTS SUSPECTED OF ENTERIC FEVER FOR MICROBE ISOLATION AND IDENTIFICATION. > The bacilli are most commonly present in the gallbladder > Spread to the environment by the stool DIAGNOSIS Specimens a) Enteric fever: blood, bone marrow, stool, urine. b) Food poisoning: stool, vomitus, suspected food. c) Septicemia: blood. Culture and identification • BLOOD CULTURES (must be taken at proper time) often positive in the first week of the typhoid fever. • BONE MARROW CULTURES yield positive results from the first to third week of the typhoid fever.
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• STOOL AND URINE CULTURE may be positive after the second week in typhoid fever. In enterocolitis, stool cultures are positive during the first week. • •
The specimens like stool and urine plated on salmonella-shigella (SS) agar directly, and blood, bone marrow need enrichment culture. After 24 hours' culture, colorless (lactose-negative) colonies are inoculated into bisugar iron agar.
WIDAL TEST 7. WHAT IS WIDAL TEST ? HOW TO INTERPRET THE RESULTS OF WIDAL TEST. WIDAL TEST A tube test for determining the quantity of agglutinating antibodies in the serum of a patient suspected of typhoid fever. > Direct diagnosis: stain, isolation and culture. Ag, DNA > Indirect diagnosis: Ab WIDAL TEST LAB DIAGNOSIS 1. Array 24 test tubes into 4 rows, 6 tubes per row. 2. Dilute the patient serum to various concentrations. 3. A.Add 0.5ml O-Ag of S.typhi to each tube of the first row. B.Add 0.5ml H-Ag of S.typhi to each tube of the second row. C.Add 0.5ml H-Ag of S.paratyphi A to each tube of the third row. D.Add 0.5ml H-Ag of S.paratyphi B to each tube of the fourth row. 3. After incubation, they are examined to note the degree of agglutination that has occurred. 4. The reciprocal of the highest dilution at which agglutination is seen is designated as the antibody titer of patient’s serum.
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BEFORE INTERPRETING THE RESULTS OF WIDAL TEST • The level of antibodies in the healthy population must be known (threshold). • Previous inoculation with TAB (typhoid, paratyphoid A, paratyphoid B) vaccine can give relatively high titers of H antibodies, as can previous infection. • Cross-reacting antibodies from previous exposure to other salmonellae sometimes give relatively high titres of O antibodies. THE RESULTS ARE INTERPRETED AS FOLLOWS : • High or rising titer of O (≥ 1: 80) and H (≥ 1: 160) suggests that active infection is present. • High titer of H (≥1: 160), but normal level for O suggests past immunization or past infection. • High or rising titer of O (≥1: 80), but normal level for H suggests early infection or cross-reaction with other bacteria. Results of serologic tests for salmonella infection must be interpreted cautiously
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16. Vibrio REFERENCE VIBRIO CHOLERA Name :: Vibrio cholera Disease caused :: CHOLERA Type :: GRAM – NEGATIVE (Oxidase-positive, which distinguishes them from enterobacteriaceae) Appearance :: COMMA SHAPED Habitat :: THE HUMAN COLON & SHELL-FISH Transmission :: By fecal-oral route Pathogenesis :: Massive, watery diarrhea caused by enterotoxin that activates adenylate cyclase by adding ADP-ribose to the stimulatory G protein. Increase in cyclic AMP causes outflow of chloride ions and water. Toxin has two components: o subunit A, which has the ADP-ribosylating activity; o subunit B, which binds the toxin to cell surface receptors. Organism produces mucinase, which enhances attachment to the intestinal mucosa. Role of endotoxin is unclear. Infectious dose is high (>107 organisms). Carrier state rare. Laboratory diagnosis :: Gram-stained smear and culture. (During epidemics,cultures not necessary.) Agglutination of the isolate with known antisera confirms the identification. Treatment :: Treatment of choice is fluid and electrolyte replacement. Tetracycline is not necessary but shortens duration and reduces carriage. Prevention :: Public health measures (e.g., sewage disposal, chlorination of the water supply, stool cultures for food handlers, and handwashing prior to food handling). Vaccine containing killed cells has limited effectiveness. Tetracycline used for close contacts.
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VIBRIO PARAHAEMOLYTICUS Name :: Vibrio parahaemolyticus Disease caused :: watery Diarrhea Type :: GRAM - negative Habitat :: found in warm sea water Transmission :: Eating contaminated raw seafood Pathogenesis :: ï‚· Diarrhea is mediated by enterotoxin similar to cholera toxin REVIEW QUESTIONS 1. DESCRIBE THE CLINCAL MANIFESTATIONS OF CHOLERA AND THE VIRULENCE FACTORS PRODUCED BY VIVRIO CHOLERAE. CLINICAL MANIFESTATION o HYPOVOLEMIC SHOCK :: Infection with V. cholerae O1 ranges from asymptomatic colonization or mild diarrheal disease to severe, rapidly fatal diarrhea. o ACIDOSIS o VOMITING o DIARRHEA o MUSCLE CRAMPS VIRULENCE FACTORS PRODUCED BY VIBRIO CHOLERAE. Liberate cholera toxin and perhaps mucinases and endotoxin Or VIRULENCE FACTOR
BIOLOGICAL EFFECT
CHOLERA TOXIN
Hypersecretion of electrolytes and water
COREGULATED PILUS
Adherence to mucosal cells adhesion
ACCESSORY COLONIZATION FACTOR
Adhesion
HEMAGGLUTINATION PROTEASE
Release bacteria from mucosal cells
ZONA OCCLUDENS
Exotoxin
ACCESSORY CHOLERA ENTEROTOXIN
Exotoxin
FLAGELLUM
Mobility
SIDEROPHORES
Iron sequestration
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17. Campylobacter Jejuni and Helicobacter Pylori REFERENCE CAMPYLOBACTER JEJUNI Name :: Campylobacter jejuni Disease caused :: ENTEROCOLITIS Type :: GRAM – negative (microaerophilic; grows at 42◦C) Habitat :: HUMAN AND ANIMAL FECES Special characteristics :: Flagella for movement Transmission :: FECAL-ORAL ROUTE Pathogenesis :: Invades mucosa of the colon but does not penetrate; therefore,sepsis rarely occurs.
No enterotoxin known.
Laboratory diagnosis :: Gram-stained smear plus culture on special agar (e.g.,Skirrow’s agar) at 42°C in high-CO2, low-O2 atmosphere.
Serologic tests not useful.
Treatment :: Usually symptomatic treatment only; erythromycin for severe disease. Prevention :: Public health measures (e.g., sewage disposal, chlorination of the water supply, stool cultures for food handlers, and handwashing prior to food handling). No preventive vaccine or drug is available.
HELICOBACTER PYLORI Name :: Helicobacter pylori Disease caused :: GASTRITIS & PEPTIC ULCER. Risk factor for gastric carcinoma Type :: GRAM – negative Appearance :: Curved Habitat :: THE HUMAN STOMACH Transmission :: BY INGESTION Pathogenesis :: Organisms synthesize urease, which produces ammonia that damages gastric mucosa. Ammonia also neutralizes acid pH in stomach, which allows the organism to live in gastric mucosa. Laboratory diagnosis :: Gram stain and culture. Urease – positive
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Serological tests for antibody “Urea breath” test Treatment :: Amoxicillin Metronidazole Bismuth (Pepto-Bismol) Prevention :: No vaccine or drug is available. REVIEW QUESTIONS 1.What kinds of diseases does Helicobacter pylori cause? 2.How do Helicobacter pylori cause diseases ? 1.What kinds of diseases does Helicobacter pylori cause? Helicobacter pylori is associated with duodenal ulcer gastric ulcers gastric carcinoma gastric lymphoma.
2.How do Helicobacter pylori cause diseases ? Flagellum --Motility –H. pylori moves into the mucus adhesin-- adhesion on gastric epithelial cells produced by H. pylori Urease production, breaks down the urea to ammonia which buffers the pH around the bacterium. Urease– ammonia—neutralization of gastric acid vacA (vacuolating associated cytotoxin A):induce epithelial cell damage and stimulate the inflammatory response. Cag A(cytotoxin associated gene A): contribute to ulcer formation Toxins and LPS may damage the mucosal cells. NH3 produced by the urease activity may also damage the cells.
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18. Anaerobic Bacteria REFERENCE SPORE-FORMING ANAEROBES Clostridia Type :: GRAM + POSITIVE Habitat :: Soil, Rust, Intestine of humans and animals Appearance :: Spore-forming rods Classification :: C. tetani -> tetanus, C.perfringens -> gas gangrene, C.botulinum -> botulism C. TETANI Name :: Clostridium tetani Disease caused :: TETANUS Type :: GRAM + POSITIVE Appearance ::Spore forming rods, Spore is at one end (“terminal spore”) so organism looks like a tennis racket. Growth :: Anarobic Habitat :: SOIL Transmission :: Enters through traumatic breaks in the skin. Pathogenesis :: Spores germinate under anaerobic conditions in the wound. Organism produces exotoxin, which blocks release of inhibitory neurotransmitters (glycine and γ-aminobutyric acid [GABA]) from spinal neurons. Excitatory neurons are unopposed, and extreme muscle spasm (tetanus, spastic paralysis) results. “LOCK-JAW” and “RISUS SARDONICUS” are two examples of the muscle spasms. Tetanus toxin (tetanospasmin) is a protease that cleaves proteins involved in the release of neurotransmitters. Laboratory diagnosis :: Primarily a clinical diagnosis. Organism is rarely i0solated. Serologic tests not useful Treatment :: Hyperimmune human globulin to neutralize toxin. Also penicillin G and spasmolytic drugs (e.g., Valium). No significant resistance to penicillin.
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Prevention ::
Toxoid vaccine (toxoid is formaldehyde-treated toxin). Usually given to children in combination with diphtheria toxoid and acellular pertussis vaccine (DTaP). If patient is injured and has not been immunized, give hyperimmune globulin plus toxoid (passive–active immunization). Debride wound. Give tetanus toxoid booster every 10 years.
C. PERFRINGES Name :: Clostridium perfringes Disease caused :: Gas gangrene (myonecrosis) and food poisoning. Type :: GRAM + POSITIVE Appearance :: Spore-forming rods Growth :: Anaerobic Habitat :: Soil and human colon. Transmission :: Myonecrosis results from contamination of wound with soil or feces. Food poisoning is transmitted by ingestion of contaminated food. Pathogenesis :: Gas gangrene in wounds is caused by germination of spores under anaerobic conditions and the production of several cytotoxic factors, especially alpha toxin, a lecithinase that cleaves cell membranes. Gas in tissue (CO2 and H2) is produced by organism’s anaerobic metabolism. Food poisoning is caused by production of enterotoxin within the gut. Enterotoxin acts as a superantigen, similar to that of S. aureus. Laboratory diagnosis :: Gram-stained smear plus anaerobic culture. Spores not usually seen in clinical specimens; the organism is growing, and nutrients are not restricted. Production of lecithinase is detected on egg yolk agar and identified by enzyme inhibition with specific antiserum. Serologic tests not useful.
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Treatment :: Penicillin G plus debridement of the wound in gas gangrene (no significant resistance to penicillin). Only symptomatic treatment needed in FOOD POISONING. Prevention :: Extensive debridement of the wound plus administration of penicillin decreases probability of gas gangrene. There is no vaccine.
C. BOTULINUM Name :: Clostridium botulinum Disease caused :: BOTULISM Type :: GRAM + POSITIVE Appearance :: Spore-forming rods Growth :: Anaerobic Habitat :: SOIL Transmission :: Organism and botulism toxin transmitted in improperly preserved food. Pathogenesis :: Botulinum toxin is a protease that cleaves proteins involved in the release of acetylcholine at the myoneural junction, causing flaccid paralysis. Failure to sterilize food during preservation allows spores to survive. Spores germinate in anaerobic environment and produce toxin. The toxin is heat-labile; therefore, foods eaten without proper cooking are usually implicated. Laboratory diagnosis :: Presence of toxin in patient’s serum or stool or in food. Detection of toxin involves either antitoxin in serologic tests or production of the disease in mice. Serologic tests for antibody in the patient are not useful. Treatment :: Antitoxin to types A, B, and E made in horses. Respiratory support may be required. Prevention :: Observing proper food preservation techniques, cooking all homecanned food, and discarding bulging cans. Objectives :: To eliminate the source of the toxin To eliminate any unabsorbed toxin To neutralize any unbound toxin with specific antitoxin To provide general supportive care.
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NON SPORE-FORMING ANAEROBES Non-spore-forming anaerobes are members of the indigenous flora in humans and animals, including G+ and G- cocci and rods. Anaerobes are present in the intestine, the mouth, the upper respiratory, and the genitourinary tract. REVIEW QUESTIONS TERMS 1. STORMY FERMENTATION In Clostridium perfringens In anaerobically-grown Litmus Milk cultures, enzymes of C. perfringens will attack the proteins and carbohydrates of the milk producing a "stormy fermentation" with clotting and a large amount of gas formation. 2. HOW DOES THE CLOSTRIDIUM TETANI CAUSE TATANUS.
OR
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Entry of C.tetani into the body usually involves implantaion of spores into a wound.
After gaining entry, C,tetani spores can persist in the body for months, waiting for the proper low oxygen growth conditions to develop
C.tetani spores enter the body, they are again in an oxygen free environment where the can germinate. (The spores usually enter the body through a deep structure wound or cut, but animal bites or even a splinter also can allow spore entry).
The bacteria then produce tetanus toxins, which circulate in the body.
One of the toxins blocks nerve impulses that allow muscles to relax
The toxin is responsible for causing generalized tetanus, the most common form of the disease
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19. Corynebacterium REFERENCE Name :: Corynebacterium diphtheriae Disease caused :: DIPHTHERIA Type :: GRAM + (Aerobic; Non-spore forming organism) Appearance :: CLUB SHAPED Arrangement :: V or L shape Habitat :: HUMAN RESPIRATORY TRACT (In human throat) Special characteristics :: METACHROMATIC GRANULES Transmission :: via respiratory droplet Pathogenesis :: Organism secretes an exotoxin that inhibits protein synthesis by adding ADP-ribose to elongation factor-2 (EF-2). Toxin has two components: o subunit A, which has the ADP-ribosylating activity, o subunit B, which binds the toxin to cell surface receptors. Pseudomembrane in throat caused by death of mucosal epithelial cells. Laboratory diagnosis :: Swab from nose, throat and other suspected lesion must be obtain before anti-microbial drugs are administrated. Gram-stained smear and culture. Black colonies on tellurite plate. Document toxin production with precipitin test or by disease produced in laboratory animals. Serologic tests not useful. Treatment :: PENICILIN, ERYTHROMYCIN Antitoxin made in horses neutralizes the toxin. Penicillin G kills the organism. No significant resistance to penicillin. Prevention :: Toxoid vaccine (toxoid is formaldehyde-treated toxin), usually given to children in combination with tetanus toxoid and acellular pertussis vaccine(DTaP). REVIEW QUESTIONS 1. What difference is between C. diphtheriae and the other Corynebacterium? 2. What pathogenesis are C. diphtheriae for Children? 3. What mean Schick test and Elek test, respectively? 4. The mechanisms of C. diphtheriae infection. 5. Why could diphtheria toxin be used for therapy of tumors?
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1. What difference is between C. diphtheriae and the other Corynebacterium? Normally most Corynebacteria are members of the normal flora of skin and mucous membranes of human beings But in Corynebacterium diphtheria, most pathogenic bacterim is in human respiratory tract. 2. What pathogenesis are C. diphtheriae for Children? When some nontoxigenic Diphtheria organisms are infected certain bacteriophage ,the organisms get toxigenicity. Lysogenic conversion: The prophage DNA as a gene are recombined with chromosome of host cell. C. Diphtheriae occur in the respiratory tract, in wound, or on the skin. C. Diphtheriae grow on mucous membranes or in skin abrasion and produce toxin (toxemia). Toxin diffuses throughout body via blood. 3. What mean Schick test and Elek test, respectively? SCHICK TEST This test involves the injection of a minute amount of the diphtheria toxin under the skin. The absence of a reaction indicates immunity, as there are anti-toxins to neutralize diphtheria toxin . A reaction indicates no immunity. ELEK TEST
The immuno diffusion technique. It is an in vitro virulence test performed upon Corynebacterium diphtheriae. It is used to test for toxigenicity of C. diphtheriae.
-filter paper saturated with antitoxin is placed on agar plate with 20% horse serum -bacterial culture streaked at right angles to filter paper
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4. mechanisms of C. diphtheriae infection. ď Ž Cleaved to yield A/B fragment, - A (on protein elongation factor 2, inhibit protein synthesis ) -B (transmembrane and receptor binding domains) ď Ž Receptor: - rich on cardiac cells and nerve cells
5. Why could diphtheria toxin be used for therapy of tumors? Diptheria toxin is an AB exotoxins that ribosylate and inactive elongation factor 2. This inhibits protein synthesis and ultimately leads to cell death
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20. Mycobacteria REFERENCE MYCOBACTERIUM TUBERCULOSIS Name :: Mycobacterium tuberculosis Disease caused :: TUBERCULOSIS Type :: ACID FAST ROD Appearance :: Rod Growth :: Aerobic Habitat :: THE HUMAN LUNGS Special characteristics :: High lipid content of cell wall, which prevents dyes used in Gram stain from staining organism. Lipids include mycolic acids and waxD Transmission :: Via RESPIRATORY DROPLETS PRODUCED BY COUGHING. Pathogenesis :: Granulomas and caseation mediated by cellular immunity (i.e., macrophages and CD4positive T cells [delayed hypersensitivity]). Cord factor (trehalose mycolate) correlates with virulence. No exotoxins or endotoxin. Suppression of cell-mediated immunity increases risk of reactivation and dissemination. Laboratory diagnosis :: Acid-fast rods seen with Ziehl-Neelsen (or Kinyoun) stain. Slow-growing (3–6 weeks) colony on Löwenstein-Jensen medium. Organisms produce niacin and are catalase-positive. Serologic tests for antibody in patient’s serum not useful. Skin Test— o Purified protein derivative (PPD) skin test is positive if induration measuring 10 mm or more appears 48 hours after inoculation. o Induration is caused by a delayed hypersensitivity response. o Positive skin test indicates that the person has been infected but not necessarily that the person has the disease tuberculosis. Treatment :: Long-term therapy (6–9 months) with three drugs, isoniazid, rifampin,and pyrazinamide. A fourth drug, ethambutol, is used in severe cases (e.g., meningitis), in immunocompromised patients (e.g., those with AIDS), and where the chance of isoniazid-resistant organisms is high, as in Southeast Asians. Most patients become noninfectious within 2 weeks of adequate therapy. Treatment of latent (asymptomatic) infections consists of isoniazid taken for 6 to 9 months or isoniazid plus rifapentine for 3 months. Multidrug-resistant (MDR) strains have emerged and require other drug combinations. Prevention :: Bacillus Calmette-Guérin (BCG) vaccine containing live, attenuated Mycobacterium bovis organisms may prevent or limit extent of disease but does not prevent infection with M. tuberculosis. Vaccine used rarely in the United States but widely used in parts of Europe & Asia.
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REVIEW QUESTIONS 1) Describe the steps of Acid Fastness Stain. 2) What is BCG? 3) Describe the biologic characteristics of M. tuberculosis? 4) Describe the virulent factors of M. tuberculosis? 5) What is OT Test? Please explain OT result.
1) DESCRIBE THE STEPS OF ACID FASTNESS STAIN. Mycobacterium is an acid –fast rods (doesn’t stain readily, once stained they resist decolourization by acid or alcohol). It stains RED and the other bacteria are blue. ACID FAST STAIN (Ziehl-Neelsen Stain) 1) flood the slide with basic fuchsin (a red dye) in 5% phenol as a mordant. 2) heat gently for few minutes to melt the wax. 3) wash with 3% HCl in ethanol. 4) counter-stain with methylene blue.
2) WHAT IS BCG? o BCG (Bacillus Calmette-Guerin): Calmette-Guerin have cultured M. bovis into avirulent bacilli on L-J medium for 13 years. o BCG is given to children for prevention of tubercle bacilli. o It is the vaccination against TUBERCULOSIS and the treatment of some bladder cancers. o Live bacteria is used.
3) DESCRIBE THE BIOLOGIC CHARACTERISTICS OF M. TUBERCULOSIS? Biological Characteristics of M.Tuberculosis It grows very slow with a generation time of 12-15 hours. On solid media (Lowenstein-Jensen ,L-J), the colonies are raised and rough with a wrinkled surface. M. tuberculosis grow either as discrete rods or as aggregates. Virulent strains tend to grow as an aggregated long arrangement called serpentine cord.
4) DESCRIBE THE VIRULENT FACTORS OF M. TUBERCULOSIS ? Virulence factors (constituents of cell wall) o No spore, no flagellum, no exotoxin, no endotoxin, o no invasive enzyme, but special cell wall o Lipid: closely related to virulence
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a. PHOSPHOLIPID monocytes proliferate, cause tubercles b. WAX D adjuvant (not only to TB), delayed-type hypersensitivity c. SULFATIDE suppress phagosome combine with lysosome d. CORD FACTOR destroy mitochondria, cause chronic granulomatosis, suppress WBC wandering polysaccharide: Capsule; protein: antigenicity, old tuberculin; associate with wax D can cause hypersensitivity and form tubercle.
5) WHAT IS OT TEST ? PLEASE EXPLAIN OT RESULT. o OT: old tuberculin is a concentrated filtrate of broth in which tubercle bacilli have grown for 6 weeks. o PPD: purified protein derivatives from TB bacilli. o OT Test: Method: intracutaneous injection o Mean: immunity to disease or active disease Theory: delayed type hypersensitivity Positive reaction: reddening and thickening (> 5mm) at the site of injection after 2-3 days ,indicates cellular immunity to tubercle bacilli. After BCG vaccination ,a positive test may last for 3-7 years. • negative reaction: • (<5mm) at the site of injection after 2-3 days means: no infection or with AIDS, immunosuppressive agents, endocrine disease, etc. • Intense positive reaction: • (>15mm ) Induration ,edema, erythema in 1-2 days means: active disease >=5 mm is classified as positive in HIV-positive persons Recent contacts of TB case Persons with fibrotic changes on chest radiograph consistent with old healed TB Patients with organ transplants and other immunosuppressed patients
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21. Parvobacillus (related to respiratory tract) REFERENCE THE HEMOPHILIC SPECIES
Section 1
Name :: Haemophilus influenza Disease caused :: Sinusitis, otitis media, and pneumonia are common. Epiglottitis is uncommon, but H. influenzae is the most important cause. H. influenzae used to be a leading cause of meningitis, but the vaccine has greatly reduced the number of cases. Type :: small GRAM – NEGATIVE rods Habitat :: UPPER RESPIRATORY TRACT Transmission :: Via Respiratory droplets. Pathogenesis :: Polysaccharide capsule is the most important determinant of virulence. Unencapsulated (“untypeable”) strains cause mucosal infections but not invasive infections. IgA protease is produced. Most cases of meningitis occur in children younger than 2 years of age, because maternal antibody has waned and the immune response of the child to capsular polysaccharides can be inadequate. No exotoxins identified. Laboratory diagnosis :: Gram-stained smear plus culture on chocolate agar. Growth requires both factors X and V. Determine serotype by using antiserum in various tests (e.g., latex agglutination). Capsular antigen can be detected in serum or cerebrospinal fluid. Serologic test for antibodies in patient’s serum not useful. Treatment :: Ceftriaxone is the treatment of choice for meningitis. Approximately 25% of strains produce β-lactamase Prevention :: Vaccine containing the type b capsular polysaccharide conjugated to diphtheria toxoid or other protein is given between 2 and 18 months of age. Rifampin can prevent meningitis in close contacts.
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BORDETELLAE
Section 2
Name :: Bordetella pertussis Disease caused :: WHOOPING COUGH (pertussis) Type :: small GRAM- NEGATIVE rods Habitat :: THE HUMAN RESPIRATORY TRACT Transmission :: Via Respiratory Droplets Pathogenesis :: Pertussis toxin stimulates adenylate cyclase by adding ADP-ribose onto the inhibitory G protein. Toxin has two components: subunit A, which has the ADP-ribosylating activity, and subunit B, which binds the toxin to cell surface receptors. Pertussis toxin causes lymphocytosis in the blood by inhibiting chemokine receptors. Inhibition of these receptors prevents lymphocytes from entering tissue, resulting in large numbers being retained in the blood. Inhibition of chemokine receptors occurs because pertussis toxin ADP-ribosylates the inhibitory G protein which prevents signal transduction within the cell. In addition, extracellular adenylate cyclase is produced, which can inhibit killing by phagocytes. Tracheal cytotoxin damages ciliated epithelium of respiratory tract. Laboratory diagnosis :: Gram-stained smear plus culture on Bordet-Gengou agar. Identified by biochemical reactions and slide agglutination with known antisera. PCR tests, if available, are both sensitive and specific. Serologic tests for antibody in patient’s serum not useful. Treatment :: Azithromycin Prevention :: The acellular vaccine containing pertussis toxoid and four other purified proteins is recommended rather than the killed vaccine, which contains whole organisms. Usually given to children in combination with diphtheria and tetanus toxoids (DTaP). Azithromycin is useful in unimmunized people who are known to be exposed.
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LEGIONELLA
Section 3
Name :: Legionella pneumophila Disease caused :: Legionnaires’ disease (‘atypical’ pneumonia) Type :: GRAM – NEGATIVE rods, but stain poorly with standard Gram stain. Required increased iron and cysterine for growth in culture. 16 serogroups; most cases caused by serogroup 1. Appearance :: * Arrangement :: * Habitat :: ENVIRONMETAL WATER SOURCES Special characteristics :: * Transmission :: Via aerosol from the water source. Person to person transmission do not occur. Pathogenesis :: Aside from endotoxin, no toxins, enzymes, or virulence factors are known. Predisposing factors include being older than 55 years of age, smoking, and having a high alcohol intake. Immunosuppressed patients (e.g., renal transplant recipients) are highly susceptible. The organism replicates intracellularly; therefore, cell-mediated immunity is an important host defense. Smoking damages alveolar macrophages, which explains why it predisposes to pneumonia. Laboratory diagnosis :: Microscopy with silver impregnation stain or fluorescent antibody. Culture on charcoal yeast extract agar containing increased amounts of iron and cysteine. Urinary antigen provides rapid diagnosis for serogroup 1 bacteria only. Diagnosis can be made serologically by detecting rise in antibody titer in patient’s serum Treatment :: Azithromycin or erythromycin. Rifampin can be added in severe cases Prevention :: No vaccine or prophylactic drug is available.
REVIEW QUESTIONS 1. What factors does H.influenza require for growth? What is satellite phenomenon? 2. Pertussis can be divided into three stages. What are they? In addition, describe the characteristics of each stage. 3. Where could we find Legionellae in nature? 4. Cell-mediated immune response but not humoral immunity plays an important role in fighting against Legionellae infection. Why?
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1. What factors does H.influenza require for growth? What is satellite phenomenon? The factors required for growth of H.influenza are :: X-factor Act physiological as heme V-factor Coenzyme I or II Satellite phenomenon On blood agar，around staphylococcal colonies，the colonies of H.influenza grow much larger。 This is satellite phenomenon.
2. Pertussis can be divided into three stages. What are they? In addition, describe the characteristics of each stage. 1. “CATARRHAL STAGE” with mild coughing and sneezing, after a starting period of about 2 weeks. The patient is highly infectious, but not very ill. 2. “PAROXYSMAL STAGE " the cough develops its explosive character and the characteristic "whoop” upon inhalation. This leads to rapid exhaustion and may be associated with vomiting，cyanosis，and convulsion 3. “recovery stage "
3. Where could we find Legionellae in nature? The natural habitats for legonellae are lakes，streams，rivers，and especially thermally heated bodies of water and soil.
4. Cell-mediated immune response but not humoral immunity plays an important role in fighting against Legionellae infection. Why? Legionellae are facultative intracellular parasites that can multiply in alveolar macrophages and monocytes. Immunity to disease is primarily cell-mediated, with humoral immunity playing a minor role.
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22. Zoonotic Bacteria REFERENCE Disease
ANTHRAX
BOVINE TUBERCULOSIS BRUCELLOSIS
CAMPYLOBACTER INFECTION
Etiologic Agent
Usual Reservoir
Usual mode of transmission to human
Bacillus anthracis
Cattle, sheep, goats
Infected animals or products
No
Mycobacterium bovis
Cattle
Milk
No
Brucella spp
Cattle, swine, goats
Milk, infected carcasses
No
Wild Contaminated mammals, food and cattle, water sheep, pets
Yes
C. jejuni
Transmission Special between Characteristics Human
LEPTOSPIROSIS
Leprospira spp
Cattle, rodents
Water contaminated with urine
No
LYME DISEASE
Borrelia burgdoferi
Deer, rodents
Ticks;
No
Pasteurella multocida
Animal oral cavities
Bites, scratches
No
PLAGUE
Yersinia pestis
Rodents
Fleas
Yes
OTHER YERSINIA INFECTION
Y. enterocolitica,
Fecal-oral
Yes
PASTEURELLOSIS
Wild Y. mammals, pseudotuberculosis pigs, cattle, pets
transplacentally
RELAPSING FEVER
Borrelia spp
Rodents, ticks
Ticks
Yes
SALMONELLOSIS
Salmonella serotypes
Poultary, livestocks
Contaminated food
Yes
RICKETTSIAL SPOTTED FEVER
R. rickettsii
Rodents, ticks, mites
Ticks, mites
No
MURINE TYPHUS
Rickettsia typhi
Rodents
Fleas
No
Resistant spores
Relapsing disease
Great epidemic potential
Epidemic potential
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Q FEVER
Coxiella burnetti
Cattle, sheep, goats
Contaminated dust and aerosols
No
BACILLUS ANTHRACIS
Section 1
Name :: Bacillus anthracis Disease caused :: ANTHRAX Type :: GRAM + POSITIVE Growth :: Aerobic Habitat :: SOIL Special characteristics :: Capsule composed of poly-D-glutamate. B. anthracis is the only medically important organism that has a capsule composed of amino acids rather than polysaccharides Transmission :: By contact with infected animals or inhalation of spores from animal hair and wool. Pathogenesis :: Anthrax toxin consists of three proteins: edema factor, which is an adenylate cyclase; lethal factor, which kills cells by inhibiting a signal transduction protein involved in cell division; and protective antigen, which mediates the entry of the other two components into the cell. The capsule is antiphagocytic. Laboratory diagnosis :: Gram-stained smear plus aerobic culture on blood agar. B.anthracis is nonmotile, in contrast to other Bacillus species. Rise in antibody titer in indirect hemagglutination test is diagnostic. Treatment :: Penicillin G (no significant resistance) Prevention :: Vaccine consisting of protective antigen is given to individuals in high-risk occupations.
BRUCELLA
Section 2
Name :: Brucella species (eg: Brucella abortus, Brucella suis, Brucella melitensis) Disease caused :: BRUCELLOSIS (undulant fever) Type :: small GRAM – NEGETIVE rods. Habitat :: Reserviour is domestic livestock Transmission :: Via unpasteurized milk and cheese or direct contact with the infected animal. Pathogenesis :: Organisms localize in reticuloendothelial cells, especially the liver and spleen.
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Able to survive and replicate intracellularly. No exotoxins. Predisposing factors include consuming unpasteurized dairy products and working in an abattoir. Laboratory diagnosis :: Gram-stained smear plus culture on blood agar plate. Identified by biochemical reactions and by agglutination with known antiserum. Diagnosis may be made serologically by detecting antibodies in patient’s serum. Treatment :: Tetracycline plus rifampin Prevention :: Pasteurize milk; vaccinate cattle. No human vaccine is available. YERSINA
Section 3
Name :: Yersinia pestis Disease caused :: BUBONIC and PNEUMONIC PLAGUE Type :: small GRAM – NEGATIVE rods with bipolar (“safety pin”) staining. One of the most virulent organisms (ie, very low ID50). Habitat :: Reservoir is wild rodents (eg: rats, prairie dogs, squirrels). Transmission is by flea bite. Pathogenesis :: Virulence factors include endotoxin, an exotoxin, two antigens (V and W), and an envelope (capsular) antigen that protects against phagocytosis. V and W proteins allow organism to grow within cells. Bubo is a swollen inflamed lymph node, usually located in the region of the flea bite. Laboratory diagnosis :: Gram-stained smear. Other stains (e.g., Wayson’s) show typical “safety-pin” appearance more clearly. Cultures are hazardous and should be done only in specially equipped laboratories. Organism is identified by immunofluorescence. Diagnosis can be made by serologic tests that detect antibody in patient’s serum. Treatment :: Streptomycin either alone or in combination with doxycycline. Strict quarantine for 72 hours. Prevention :: Control rodent population and avoid contact with dead rodents. Killed vaccine is available for persons in high-risk occupations. Close contacts should be given tetracycline.
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FRANCISELLA TULARENSIS
Section 4
Name :: Francisella tularensis Disease caused :: TULAREMIA Type :: small GRAM – NEGATIVE rods Habitat :: Reservoir is many species of wild animals, especially rabbits, deer and rodents. Transmission :: By ticks (eg: Dermacentor), aerosols, contact and ingestion. Pathogenesis :: Organisms localized in reticuloendothelial cells. No exotoxins Laboratory diagnosis :: Culture is rarely done because special media are required and there is a high risk of infection of laboratory personnel. Diagnosis is usually made by serologic tests that detect antibodies in patient’s serum. Treatment :: Streptomycin Prevention :: Live, attenuated vaccine for persons in high-risk occupations. Protect against tick bites REVIEW QUESTIONS 1) 2) 3) 4) 5)
Zoonosis. Please list three kinds of bacteria related with zoonosis. Describe the component of anthrax toxin. How dose the anthrax toxin work? Classification of anthrax according to the route of entry Please describe three kinds of Yersinia that may cause human diseases. Please describe antigens related to pathogenesis in Y. pestis, and the corresponding function of each antigen. 6) Please describe three kinds of plagues induced by Y. pestis infection. 1. ZOONOSIS. PLEASE LIST THREE KINDS OF BACTERIA RELATED WITH ZOONOSIS. ZOONOSIS o Zoonosis are human diseases caused by organisms that are acquired from animals. o Some zoonotic organisms are acquired directly from the animal reservoir, whereas others are transmitted by vectors, such as mosquitoes, fleas, or ticks. THREE KINDS OF BACTERIA RELATED WITH ZOONOSIS ARE :: o BACILLUS o BRUCELLA o YERSINIA
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2. DESCRIBE THE COMPONENT OF ANTHRAX TOXIN. HOW DOSE THE ANTHRAX TOXIN WORK? Anthrax toxin: the complex (PA+LF+EF) Protective Antigen (PA) Lethal Factor (LF) Edema Factor (EF) The complex (PA+LF or PA+EF) is internalized by endocytosis acidification of the endosome the LF or EF cross the membrane into the cytosol via PA-mediated ion-conductive channels WORKING OF ANTHRAX TOXIN 1. Effects of anthrax exotoxins on macrophages Edema toxin is a calmodulin dependent adenylate cyclase increases intracellular levels of cyclic AMP (cAMP) on entry types of cell This is believed to alter water homeostasis
that into most
resulting in massive edema 2. Effects of anthrax exotoxins on macrophages Lethal toxin is a zinc metallo-protease that causes a hyperinflammatory condition in macrophages responsible for shock and death.
MAPKK denotes mitogen-activated protein kinase • •
Endospores are phagocytosed by macrophages and germinate Macrophages containing bacilli detach and migrate to the regional lymph node.
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3. CLASSIFICATION OF ANTHRAX ACCORDING TO THE ROUTE OF ENTRY GASTROINTESTINAL ANTHRAX o The ingestion of poorly cooked meat or milk from infected animals. o Initial signs of nausea, loss of appetite, vomit, and fever are followed by abdominal pain, vomit of blood, and severe diarrhea. PULMONARY ANTHRAX o Inhalation of spore-containing dust where animal hair or hides are being handled . o Begins abruptly with high fever and chest pain, progresses rapidly to a systemic hemorrhagic pathology . Gastrointestinal and pulmonary anthrax are more dangerous than the cutaneous form because they are usually identified too late for treatment to be effective
4. PLEASE DESCRIBE THREE KINDS OF YERSINIA THAT MAY CAUSE HUMAN DISEASES. Genus YERSINIA Y. pestis Y. enterocolitica Y. pseudotuberculosis
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5. PLEASE DESCRIBE ANTIGENS RELATED TO PATHOGENESIS IN Y. PESTIS, AND THE CORRESPONDING FUNCTION OF EACH ANTIGEN. PATHOGENSIS
ANTIGEN STRUCTURE o F1 Antigen: ANTI-PHAGOCYTOSIS o V,W Antigen: ANTI-PHAGOCYTOSIS o Yersinia Outer membrane Protein (Yop): play an important ROLE IN DESTROYING HOST DEFENSE SYSTEM. o Murine Toxin (MT): DO DAMAGE TO CARDIOVASCULAR SYSTEM, LEADING TO SEPTIC SHOCK. 0.3%-0.4% formaldehyde Toxoid o Endotoxin (LPS): INDUCE INFLAMMATION, LEADING TO SEPTIC SHOCK, DIC, etc.
6. PLEASE DESCRIBE THREE KINDS OF PLAGUES INDUCED BY Y. PESTIS INFECTION. Three kinds of plagues induced by Y.pestis infection BUBONIC PLAGUE: High fever, Swelling, Bleeding, Necrosis of lymph nodes PNEUMONIC PLAGUE: Chills, cough, respiratory failure, circulatory collapse ——Black Death SEPTICEMIC PLAGUE: Fever (39-40 ˚C) , Shock , DIC
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23. Other Bacteria REFERENCE PSEUDOMONAS Name :: Pseudomonas aeruginosa Disease caused :: Wound infection, UTI, pneumonia, and sepsis. One of the most important causes of nosocomial infections, especially in burn patients and those with cystic fibrosis. Causes endocarditis in intravenous drug users. Type :: GRAM negative rods Growth :: Anerobic Habitat :: Environmental water sources (eg: In hospital respirators and humidifiers). Also inhabits the skin, upper respiratory tract, and colon of about 10% people. Special characteristics :: Non–lactose-fermenting. Pyocyanin (bluegreen) pigment produced. Oxidase-positive, which distinguishes it from members of the Enterobacteriaceae family Transmission :: Via water aerosols, aspiration, fecal contamination Pathogenesis :: Endotoxin is responsible for fever and shock associated with sepsis. Produces exotoxin A, which acts like diphtheria toxin (inactivates EF-2). Pili and capsule are virulence factors that mediate attachment and inhibit phagocytosis. Glycocalyx-producing strains predominate in chronic infections in cystic fibrosis patients. Strains with type III secretion systems are more virulent than those without. Severe burns and neutropenia are important predisposing factors. Laboratory diagnosis :: Gram-stained smear and culture. Non–lactose-fermenting colonies on EMB or MacConkey’s agar. TSI agar shows an alkaline slant and an alkaline butt because the sugars are not fermented. Oxidase-positive. Serologic tests not useful Treatment ::
Antibiotics must be chosen on the basis of antibiotic sensitivities because resistance is common. Anti-pseudomonal penicillin and aminoglycoside are often used. Resistance is mediated by a variety of plasmid-encoded enzymes (e.g., β- lactamases and acetylating enzymes).
Prevention :: Disinfection of water-related equipment in the hospital, handwashing, and prompt removal of urinary and intravenous catheters. There is no vaccine. REVIEW QUESTION What kind of bacteria is the most primary nosocomial pathogen ? P.aeruginosa is most widely distributed in nature and is commonly present in hospitals in moist environments. It can colonize normal human It causes disease in human with abnormal host defenses.It is most primarily a nosocomial pathogen
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24. Actinomyces and Nocardia REFERENCE Features of Actinomycetes Genus
Morphology
Acid Fastness
Growth
Source
Disease
Actinomyces
Branching bacilli
None
Anaerobic
Oral, intestinal Endogenous flora
Chronic cellulitis, draining sinuses
Nocardia
Branching bacilli
Weaka,b
Aerobic
Soil
Pneumonia, skin pustules, brain abscess
Rhodococcus
Cocci to bacilli
Variable (weaka)
Aerobic
Soil, horsesc
Pneumonia
Streptomyces
Branching bacilli
None
Aerobic
Soil
Extremely rared
a – Modified strain, fast only to weak decolorizer (1% H2SO4) b – N.asteroides and N.brasiliensis; other species variable c – R. equi. d – Non pathogen but important producer of antibiotcs.
ACTINOMYCES
Section 1
Name :: Actinomyces israelii Disease caused :: ACTINOMYCOSIS (abscesses with draining sinus tracts) Type :: GRAM + POSITIVE filamentous Appearance :: Branching rods Growth :: Anaerobic Habitat :: THE HUMAN MOUTH, especially anaerobic crevices around the teeth. Transmission :: Into tissues occurs during dental disease or trauma. Organism also aspirated into lungs, causing thoracic actinomycosis. Retained intrauterine device (IUD) predisposes to pelvic actinomycosis. Pathogenesis :: No toxins or virulence factors known. Organism forms sinus tracts that open onto skin and contain “sulfur granules,” which are mats of intertwined filaments of bacteria. Laboratory diagnosis :: Gram-stained smear plus anaerobic culture on blood agar plate. “Sulfur granules” visible in the pus. No serologic tests. Treatment :: Penicillin G and surgical drainage. Prevention :: No vaccine or drug is available.
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NOCARDIA
Section 2
Name :: Nocardia asteroides Disease caused :: Nocardiosis (especially lung and brain abscesses) Type :: GRAM + POSITIVE filamentous ; weakly Acid-fast Appearance :: Branching rods Growth :: Aerobic Habitat :: SOIL Transmission :: Via Airborne particles, which are inhaled into the lungs. Pathogenesis :: No toxins or virulence factors known. Immunosuppression and cancer predispose to infection. Laboratory diagnosis :: Gram-stained smear and modified Ziehl-Neelsen stain. Aerobic culture on blood agar plate. No serologic tests. Treatment :: SULFONAMIDES Prevention :: No vaccine or drug is available. REVIEW QUESTIONS Sulfur granule Mycetoma Compare the characteristics of Actinomyces and Norcadia. SULFUR GRANULE yellow orange granule, named for its gross resemblance to a grain of sulfur . It is solidified with elements of tissue exudate. It is a small Actinomyces colony of intertwined branching filaments.
MYCETOMA 1. chronic inflammation of the tissues caused by infection with a fungus or with certain bacteria.
COMPARE THE CHARACTERISTICS OF ACTINOMYCES AND NORCARDIA Common: gram positive, branching bacillus, opportunists Actinomyces: No acid fastness, anaerobic growth Nocardia: Weak acid fastness, aerobic growth
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25. Spirochetes REFERENCE o The order spirochaetales is subdivided into two families and eight genera, of which three are responsible for human disease. o Treponema (8-14 regular spirals) o Borrelia (5-10 irregular spirals) o Leptospira (>14 spirals)
TREPONEMA PALLIDUM Name :: Treponema Pallidum Disease caused :: SYPHILIS Type :: SPIROCHETES. Not seen on Gram-stained smear because organism is too thin. Not cultures in vitro. Habitat :: THE HUMAN GENITIAL TRACT Special characteristics :: 8-14 small, regular spirals; actively motile. In tissues stained by a silver impregnation method. The spirals are not readily seen unless immunofluorescent stain or dark field illumination is employed. Transmission ::
ACQUIRED SYPHILIS :: By sexual contact CONGENITAL SYPHILIS :: From mother to fetus across the placenta
Pathogenesis :: Organism multiplies at site of inoculation and then spreads widely via the bloodstream. Many features of syphilis are attributed to blood vessel involvement causing vasculitis. Primary (chancre) and secondary lesions heal spontaneously. Tertiary lesions consist of gummas (granulomas in bone, muscle, and skin), aortitis, or central nervous system inflammation. No toxins or virulence factors known. Laboratory diagnosis :: Seen by dark field microscopy or immunofluorescence. Serologic tests important: VDRL and RPR are nontreponemal (nonspecific) tests used for screening; FTA-ABS is the most widely used specific test for Treponema pallidum. Antigen in VDRLand RPR is beef heart cardiolipin; antigen in FTA-ABS is killed T. pallidum. VDRL declines with treatment, whereas FTA-ABS remains positive for life.
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Treatment :: Penicillin is effective in the treatment of all stages of syphilis. In primary and secondary syphilis, use benzathine penicillin G (a depot preparation) because T. pallidum grows slowly, so drug must be present for a long time. There is no resistance. Prevention :: Benzathine penicillin given to contacts. No vaccine is available. BORRELIA BURGDORFERI Name :: Borrelia burgdorferi Disease caused :: LYME DISEASE Type :: SPIROCHETES. Gram-stained not useful. Can be cultured in vitro, but not usually done. Habitat :: Main reservoir is WHITE-FOOTED MOUSE Transmission :: By the bite of IXODID TICKS. Very small nymph stage of ixodid tick (deer tick) is most common vector. Tick must feed for at least 24 hours to deliver an infectious dose of B.burgdorferi Pathogenesis :: Organism invades skin, causing a rash called erythema migrans. It then spreads via the bloodstream to involve primarily the heart, joints, and central nervous system. No toxins or virulence factors identified. Laboratory diagnosis :: Diagnosis usually made serologically (i.e., by detecting IgM antibody). Confirm positive serologic test with Western blot assay. Treatment :: Doxycycline for early stages; Penicillin G for late stages Prevention :: Vaccine containing outer membrane protein of the organism was available but has been withdrawn. Avoid tick bite. Can give doxycycline or amoxicillin to people who are bitten by a tick in endemic areas.
LEPROSPIRA INTERROGANS Name :: Leprospira interrogans Disease caused :: LEPROSPIROSIS Type :: Spirochetes that can be seen on dark field microscopy but not light microscopy. Can be cultured in vitro. Habitat :: WILD AND DOMESTIC ANIMALS Transmission :: Via Animal urine
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Pathogenesis :: Two phases: o an initial bacteremic phase o a subsequent immunopathologic phase with meningitis. No toxins or virulence factors known. Laboratory diagnosis :: Dark field microscopy and culture in vitro are available but not usually done. Diagnosis usually made by serologic testing for antibodies in patient’s serum. Treatment :: Penicillin G. There is no significant antibiotic resistance. Prevention ::
Doxycycline effective for short term exposure. Vaccination domestic livestock and pets. Rat control
REVIEW QUESTIONS
Describe the stages of syphilis and the main characteristics of each stage. Reagin What two kinds of syphilis are there? Please say three kinds of human diseases related to SPSPIROCHETES infection.
DESCRIBE THE STAGES OF SYPHILIS AND THE MAIN CHARACTERISTICS OF EACH STAGE. Acquire Syphilis are classified into :: 1) PRIMARY STAGE Period :: 10 to 60 days Primary lesion – chancre Area of ulceration / inflammation Many organism Rich in TP A predominance of lymphocytes and plasma cells Hard chancre Highly Infectious Heal spontaneously Appears up to 3 weeks post exposure Heals in 2 to 6 weeks If untreated, 40% of patients go on to develop secondary syphilis 2) SECONDARY STAGE Period :: 2 to 10 weeks after primary stage o Systemic spread o Flu-like symptoms o Skin, particularly o Many organism
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Rich in TP Red maculopapular rash anywhere on the body Infectious highly Subside spontaneously 2º syphilis develops 2-6 weeks after appearance of a chancre Rashes on palms/soles Lymphadenopathy, flu-like symptoms If still untreated, 2º syphilis may be followed by tertiary syphilis. 3) TERTIARY STAGE Period :: Several years later. 3- 5 years after infection Skin, central nervous system Delayed hypersensitivity Few organisms Control by immune response Few TP Granulomatous lesions in skin, bone and liver Degenerative changes in central nervous Cardiovascular lesion Tertiary syphilis develops 4 or more years after untreated primary syphilis Tertiary syphilis (late syphilis) may affect many parts of the body
REAGIN T. pallidum also cause the development of a distinct antibody-like substance, reagin. Reagin gives positive reaction with cardiolipin extracted from normal mammalian tissues.
WHAT ARE THE TWO KINDS OF SYPHILIS ? ACQUIRED SYPHILIS transmitted by intimate contact（sexual contact） CONGENITAL SYPHILIS transmitted from pregnant women to their fetuses.
PLEASE SAY THREE KINDS OF HUMAN DISEASES RELATED TO SPIROCHETES INFEECTION. The three kinds of Spirochetes that are responsible for Human disease are as follows :: 1. Treponema SYPHILIS 2. Borrelia LYME DISEASE 3. Leptospira LEPROSPIROSIS
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26. Chlamydiae .REFERENCE CHLAMYDIA TRACHOMATIS Name :: Chlamydia trachomatis Disease caused :: Nongonococcal urethritis, cervicitis, inclusion conjunctivitis,lymphogranuloma venereum, and trachoma. Pneumonia in infants. Type :: OBLIGATE INTRACELLULAR PARASITES. Not seen in Gramstained smear. Exists as inactive elementary body extracellular and as metabolically active, dividing reticulate body intracellularly. Habitat :: THE HUMAN GENITIAL TRACTS and EYES. Transmission :: By sexual contact and during passing of neonate through birth canal. Transmission in trachoma is chiefly by hand-to-eye contact. Pathogenesis :: No toxins or virulence factors known Laboratory diagnosis :: Nucleic acid amplification test (NAAT) using the patient’s urine is used to diagnose chlamydial sexually transmitted disease. Cytoplasmic inclusions seen on Giemsa-stained or fluorescent antibody–stained smear of exudate. PCR-based assay is available. Organism grows in cell culture and embryonated eggs, but these are not often used. Treatment :: A tetracycline (e.g., doxycycline) or a macrolide (e.g., azithromycin). Prevention :: Erythromycin effective in infected mother to prevent neonatal disease. No vaccine is available.
CHLAMYDIA PNEUMONIAE Name :: Chlamydia pneumoniae Disease caused :: A TYPICAL PNEUMONIA Type :: OBLIGATE INTRACELLULAR PARASITES. Not seen in Gram-stained smear. Exists as inactive elementary body extracellular and as metabolically active, dividing reticulate body intracellularly. Habitat :: THE HUMAN RESPIRATORY TRACT. Transmission :: By respiratory aerosol Pathogenesis :: No toxins or virulence factors known. Laboratory diagnosis :: Serologic tests for antibody inpatient’s serum. Treatment :: A tetracycline, such as doxycycline. Prevention :: No vaccine or drug is available.
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REVIEW QUESTIONS 1. What are chlamydiae, the reticulate body, the elementary body ? 2. What is the developmental cycle of chlamydiae? 3. List 3 bacterial diseases transmitted by sexual intercourse
WHAT ARE CHLAMYDIAE, THE RETICULATE BODY, THE ELEMENTARY BODY ? CHLAMYDIAE The chlamydiae are small and are obligate intracellular parasites of eukaryotic cells. They are round shaped and gram-negative, they possess a distinctive developmental cycle. RETICULATE BODY (RB) a large intracytoplasmic replicating form and devoid of an electron-dense nucleoid. ELEMENTARY BODY (EB) a small nonreplicating, infectious particle with an electron-dense nucleoid.
WHAT IS THE DEVELOPMENTAL CYCLE OF CHLAMYDIAE ? EBs attach to the susceptive cells. Penetration into the host cell via endocytosis forming phagosomes. EBs reorganize into the metabolically active RBs. RBs replicate by binary fission and inclusion body. RBs begin reorganizing into EBs. Cell ruptures and releases the infective EBs. The developmental cycle takes 24～ 48 hours.
LIST 3 BACTERIAL DISEASES TRANSMTTED BY SEXUAL INTERCOURSE. 1. CHLAMYDIAE 2. LYMPHOGRANULOMA VENEREUM 3. TRACHOMA
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27. Mycoplasmas REFERENCE MYCOPLASMA Name :: Mycoplasma pneumoniae Disease caused :: “Atypical” pneumonia Habitat :: THE HUMAN RESPIRATORY TRACT Special characteristics :: Smallest free-living organisms. Not seen on Gram-stained smear because they have no cell wall, so dyes are not retained. Penicillins and cephalosporins are not effective because there is no cell wall (peptidoglycan). The only bacteria with cholesterol in cell membrane. Can be cultured in vitro. Transmission :: Via Respiratory droplet Pathogenesis :: No exotoxins produced. No endotoxin because there is no cell wall. Produces hydrogen peroxide, which may damage the respiratory tract. Laboratory diagnosis :: Gram stain not useful. Can be cultured on special bacteriologic media but takes at least 10 days to grow, which is too long to be clinically useful. Positive cold–agglutinin test is presumptive evidence. Complement fixation test for antibodies to Mycoplasma pneumoniae is more specific. Treatment :: AZITHROMYCIN or DOXYCYCLINE Prevention :: No vaccine or drug is available.
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REVIEW QUESTIONS ď Ž What differences are Mycoplasma and L Form Bacteria? ď Ž What is Mycoplasma
WHAT DIFFERENCES ARE MYCOBACTERIUM AND L FORM BACTERIA ? MYCOPLASMA
L-FORM BACTERIA
No genetic relationship with bacteria
Relate to their parent bacteria, sometimes can revert
Cholesterol for their cell membrane
No cholesterol for their cell membrane
Stable in ordinary medium Grow slowly, colony small (diameter 0.10.3mm) Low turbidity in liquid medium
Need hyperosmotic solution Colony larger(diameter 0.5-1.0mm) High turbidity in liquid medium, may adhere to the wall or bottom of the tube
WHAT IS MYCOPLASMA ? o o o o o o
A group of the smallest organisms that can be free-living in nature. Pass bacterial filter. Be lack of cell wall Grow in laboratory media. Many species are part of the normal flora. These organisms are frequent cell culture contaminants.
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28. Rickettsia REFERENCE RICKETTSIA Name :: Rickettsia prowazekii Disease caused :: Typhus. Type :: GRAM-NEGATIVE. OBLIGATE INRACELLULAR PARASITES. Not seen well on Gram-stained smear. Antigens cross-react with OX strains of Proteus vulgaris (Weil-Felix reation). Habitat :: Human as reservoir Transmission :: Via the bite of the human body louse Pathogenesis :: No toxins or virulence factors known. Laboratory diagnosis :: Serologic tests for antibody in patient’s serum. Treatment :: Tetracycline, such as doxycycline Prevention :: A killed vaccine is used in the military but is not available for civilian use
REVIEW QUESTION WHAT DOES WEIL-FELIX TEST MEAN?
The Weil–Felix test is an agglutination test for the diagnosis of rickettsial infections. P.vulgaris strains (OX-19, OX-K, OX-2)have common antigen with Rickettsia (Weil-Felix test). The Weil-Felix test is useful to identify a R. prowazekii infection (anti-Rickettsia antibody)
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29. General Properties of Viruses REVIEW QUESTIONS 1. 2. 3. 4. 5. 6. 7.
WHAT IS VIRION ? WHAT IS NUCLEOCAPSID? WHAT IS VIRAL ENVELOPE? COMPARE NAKED VIRUS WITH ENVELOPED VIRUS. DESCRIBE THE FUNCTION OF VIRAL STRUCTURAL PROTEIN. DESCRIBE THE FUNCTION OF VIRAL NUCLEIC ACIDS. DESCRIBE THE SYMMETRY OF VIRAL CAPSID PROTEIN.
1. WHAT IS VIRION ? Virion is the complete mature and infectious viral particles.
2. WHAT IS NECLEOCAPSID ? > Viral basic structure. > The combination of viral core and viral protein capsid.
3. WHAT IS VIRAL ENVELOPE? > Viral special structure. > Membrane structure from host cell (cell origin). > Membrane structure anchored viral proteins (virus origin).
4. COMPARE NAKED VIRUS WITH ENVELOPED VIRUS. • Naked Virus: be composed of nucleocapsid. • Enveloped Virus: be composed of nucleocapsid + envelope.
Naked Virus
Enveloped Virus
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5. DESCRIBE THE FUNCTION OF VIRAL STRUCTURAL PROTEIN. • • • •
Protect the viral nucleic acid. Participate in the viral infection. Present the antigenicity. Maintain the structural integrity.
6. DESCRIBE THE FUNCTION OF VIRAL NUCLEIC ACIDS. • • •
encodes the genetic information necessary for replication of the virus. Control the viral heredity and variation. Be responsible for the infectivity of virus.
7. DESCRIBE THE SYMMETRY OF VIRAL CAPSID PROTEN. • • •
helical symmetry. icosahedral or cubic symmetry. complex structure.
8. WHAT IS PRION? • •
Infectious protein encoded by a single cellular gene. No nucleic acid. Cause central nervous system diseases(mad cow disease, creutzfeldtJakob disease).
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30. Multiplication and variation of Viruses (VIRAL REPLICATION) REVIEW QUESTIONS 1. WHAT IS VIRAL INTERFERENCE ? 2. VIRAL REPLICATIVE CYCLE CAN BE DIVIDED INTO SEVERAL STAGES ? 3. WHAT IS VIRAL BUDDING ?
1. WHAT IS VIRAL INTERFERENCE ? • When two viruses infect one cell at the same time. • the virus A may inhibit replication of virus B. • this phenomenon is called viral interference. 2. VIRAL REPLICATIVE CYCLE CAN BE DIVIDED INTO SEVERAL STAGES ? –
ADSORPTION and PENETRATION.
–
UNCOATING.
–
BIOSYNTHESIS.
–
ASSEMBLY and RELEASE.
3. WHAT IS VIRAL BUDDING? • •
Release of virions: There are many ways. Enveloped viruses: release their nucleocapsids and acquire their envelope from infected-cell membrane.
4. BRIEFLY DESCRIBES THE MAIN CHARACTERISTICS OF THE VIRAL ADSORPTION TO SUSCEPTIBLE CELLS. • characteristics: specificity. • adsorption: viral surface protein binds with corresponding receptors on the susceptible cell. • example: HIV gp120-------CD4 molecule, T cell.
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31. Viral Infection and Immunity REVIEW QUESTIONS 1. 2. 3. 4. 5. 6. 7. 8.
Describe the modes of viral transmission. Describe the type of the virus persistent infection. What is Viral neutralizing antibody? Describe antiviral mechanism of Interferon. How do you understand the immune function in viral infection? Describe the effects of viral infection on cell. Describe the humoral immunopathology in some viral infections. Describe the cell-mediated immunopathology in some viral infections.
1. DESCRIBE THE MODES OF VIRAL TRANSMISSION. • Horizontal transmission: The viruses spread directly in the crowd. • Vertical transmission: the transmission of virus from mother to off-spring.
2. DESCRIBE THE TYPE OF THE VIRUS PERSISTENT INFECTION. • Definition: viruses persist in the host for long time period, even for whole life. • Types: • Chronic infection • Latent infection • Slow virus infection.
3. WHAT IS VIRAL NEUTRALIZING ANTIBODY? An antibody that is capable of keeping a virus from infecting a cell by inhibiting its adsorb or penetrate to cells.
4. DESCRIBE ANTIVIRAL MECHANISM OF INTERFERON. • Interferon induce cell to produce anti-virus pr;oteins. • These proteins(protein kinase R, 2'5'A synthetase) degrade viral RNA and inhibit viral protein synthesis. • Virus be unable to multiply in these cells.
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5. HOW DO YOU UNDERSTAND THE IMMUNE FUNCTION IN VIRAL INFECTION? • • • •
The immune response to the virus probably has the greatest impact on the outcome of infection. In the most cases, the virus is cleared completely from the body and results in complete recovery. In some situations, viral diseases are induced by immunopathology. In other infections, the immune response is unable to clear the virus completely and the virus persists.
6. DESCRIBE THE EFFECTS OF VIRAL INFECTION ON CELL. • Cytocidal Effect • Steady State Infection • Integration And Transformation • Apoptosis
7. DESCRIBE THE HUMORAL IMMUNOPATHOLOGY IN SOME VIRAL INFECTIONS. • Response: Antigens bind with antibodies, forming IC. • Complex: Activate complement, NK cell, macrophage, Complexes deposit in basement membrane. • Disease: A large number of cells damage or injury of basement membrane.
8. DESCRIBE THE CELL-MEDIATED IMMUNOPATHOLOGY IN SOME VIRAL INFECTIONS. • Response : Virus-infected cells induce the activation of CD4+Th cell and CD8+CTL. • CD4+Th1: Release cytokines(γ-IFN, IL-2, etc ). Activate macrophage and CTL. • CD8+CTL: Specifically kill target cells (virus-infected). • Desease: induce inflammation or cause a large number of cells damage.
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34. Hepatitis viruses
REFERENCE Name :: Hepatitis A Virus Disease caused :: HEPATIITIS A Special characteristics :: Naked nucleocapsid virus with a single-stranded, positive polarity RNA. No virion polymerase. Virus has a single serotype. Transmission :: Fecal–oral route. In contrast to hepatitis B virus (HBV) and hepatitis C virus (HCV), blood-borne transmission of hepatitis A virus (HAV) is uncommon because viremia is brief and of low titer. Pathogenesis :: • The virus replicates in the GI tract and then spreads to the liver during a brief viremic period. • The virus is not cytopathic for the hepatocyte. • Hepatocellular injury is caused by immune attack by cytotoxic T cells. Laboratory diagnosis :: The most useful test to diagnose acute infection is IgM antibody. Isolation of the virus from clinical specimens is not done. Treatment :: No antiviral drug is available Prevention :: Vaccine contains killed virus. Administration of immune globulin during the incubation period can mitigate the disease Name :: Hepatitis B Virus Disease caused :: HEPATIITIS B ; implicated as a cause of hepatocellular carcinoma. Special characteristics :: Enveloped virus with incomplete circular double-stranded DNA (i.e., one strand has about one-third missing and the other strand is “nicked” [not covalently bonded]). DNA polymerase in virion. HBV-encoded DNA polymerase acts as a reverse transcriptase by using viral mRNA as the template for the synthesis of progeny genome DNA. There are three important antigens: the surface antigen, the core antigen, and the e antigen. Another protein, HBx, inactivates p53 tumor suppressor protein, a process involved in causing hepatocellular carcinoma. In the patient’s serum, long rods and spherical forms composed solely of HBsAg predominate. HBV has one serotype based on the surface antigen. Transmission Transmitted by blood, during birth, and by sexual intercourse. Pathogenesis :: • Hepatocellular injury due to immune attack by cytotoxic (CD8) T cells. Chronic carrier state occurs in 5% of adult infections but in 90% of neonatal infections because neonates have poor cytotoxic T-cell activity.
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• Chronic carrier state can lead to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. • Hepatocellular carcinoma may be related to the integration of part of the viral DNA into hepatocyte DNA and subsequent synthesis of HBx protein. • Antigen–antibody complexes cause arthritis, rash, and glomerulonephritis Laboratory diagnosis :: • HBV has not been grown in cell culture. • Three serologic tests are commonly used: surface antigen (HBsAg), surface antibody (HBsAb), and core antibody (HBcAb). • Detection of HbsAg for more than 6 months indicates a chronic carrier state. • The presence of e antigen indicates a chronic carrier who is making infectious virus. • The presence of e antigen is an important indicator of transmissibility. • An HBV-infected person who has neither detectable HBs antigen nor HBs antibody is said to be in the “window” phase. Diagnosis of this patient is made by detecting HB core antibody. Treatment :: • No treatment is given for acute hepatitis B. • For chronic hepatitis B, a reverse transcriptase inhibitor, such as tenofovir or entecavir, can reduce the inflammation associated with chronic hepatitis B but does not cure the carrier state. • A combination of tenofovir and emtricitabine is also effective. Prevention :: There are three main approaches: (1) vaccine that contains HBsAg as the immunogen; (2) hyperimmune serum globulins obtained from donors with high titers of HBsAb; and (3) education of chronic carriers regarding precautions. Passive-active immunization using both vaccine and immune globulins can prevent infection in neonates and those with needle-stick injuries. Name :: Hepatitis C Virus Disease caused :: HEPATIITIS C; associated with hepatocellular carcinoma. Special characteristics :: Enveloped virus with one piece of single-stranded, positive- polarity RNA. No polymerase in virion. HCV has multiple serotypes. Transmission :: Most transmission is perinatal or via blood. Sexual transmission is less common. Pathogenesis :: • Hepatocellular injury caused by cytotoxic T cells. • HCV replication itself does not kill cells (i.e., does not cause a cytopathic effect). • More than 50% of infections result in the chronic carrier state. • The chronic carrier state predisposes to chronic hepatitis and to hepatocellular carcinoma. Laboratory diagnosis :: Serologic testing detects antibody to HCV. A PCR-based assay for “viral load” can be used to evaluate whether active infection is present. Treatment :: Treatment of acute hepatitis C with pegylated interferon α- significantly reduce the number of patients who become chronic carriers. Treatment of chronic hepatitis C with pegylated interferon α- plus ribavirin reduces the effects of chronic hepatitis but does not eradicate the carrier state. Addition of a protease inhibitor (e.g., boceprevir or telaprevir) greatly increases effectiveness and can reduce the viral load to undetectable levels. The use of sofosbuvir, an inhibitor of the RNA polymerase of HCV is very effective in the treatment of chronic hepatitis C. Prevention :: Posttransfusion hepatitis can be prevented by discarding donated blood if antibody to HCV is detected. There is no vaccine, and hyperimmune globulins are not available.
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Feature
HEPATITIS A
HEPATITIS B
HEPATITIS C
HEPATITIS D
HEPATITIS E
Common Name
Infectious
Serum
Non A, non BDelta agent post transfusion
Enteric non A, non B
Virus Structure
Picornavirus capsid, RNA
Hepadnavirus envelope, DNA
Flavivirus envelope, RNA
Viroid like envelope, circular RNA
Calicivirus capsid, RNA
Transmission
Fecal- oral
Parenteral, sexual
Parenteral, sexual
Parenteral, sexual
Fecal – oral
Onset
Abrupt
Insidious
Insidious
Abrupt
Abrupt
Incubation period (days)
15 - 50
45 – 160
14 – 180
15 – 64
15 – 50
Severity
Mild
Occasionally severe
Usually subclinical
Co-infection with HBV
Normal Patients: mild; Pregnant women: severe
Mortality
<0.5%
1% - 2%
0.5% - 1%
High to very high
Normal patients: 1& 2% Pregnant women: 20%
Chronicity/ Carrier state
No
Yes
Yes
Yes
No
Other disease None associated
Primary hepatocellular carcinoma, cirrhosis
Primary hepatocellular carcinoma, cirrhosis
Cirrhosis fulminant hepatitis
None
Laboratory diagnosis
Symptoms & serum levels of HBsAg, HBeAg and anti-HBcIgM
Symptoms and anti-HCV ELISA
Anti-HDV ELISA
Symptoms and anti-HEV IgM
Symptoms and anti-HAV IgM
HEPATITIS A VIRUS QUESTIONS 1. DESCRIBE THE MAIN IMMUNE METHOD TO PREVENT HAV INFECTION. • Passive immunization: Injection of anti-HAV IgG (neutralizing antibody). • Active immunization: Inoculation of killed or attenuated live HAV vaccines.
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2. DESCRIBE TRANSMISSION WAY OF HAV INFECTION. Transmission way :: Fecal- oral route
3. DESCRIBE DISEASE PATTERNS AND PROGNOSIS OF HAV INFECTION. • Patterns: mild acute hepatitis. Unapparent infections are very common, especially in children. • Prognosis: no chronic form of the disease. Fulminant hepatitis is rare.
HEPATITIS B VIRUS QUESTIONS 1. WHAT IS DANE PARTICLE > Mature infectious pathogen > The virion of HBV
2. COMPARETHE DIFFERENCES BETWEEN SMALL SPHERICAL PARTICLE AND DANE PAARTICLE. • SMALL SPHERICAL PARTICLE: sphere, 22nm in diameter, HBsAg, non-infectious particle. • DANE PARTICLE: sphere, 42nm in diameter, HBsAg, HBcAg, HBeAg, DNA, infectious HBV particle.
3. DESCRIBE THE TRANSMISSION OF HBV. • sexual contact. • parenteral routes. • vertical transmission.
4. WHAT IS THE DETECTION INDEX OF ELISA FOR HBV ? • HBsAg, Anti-HBs. • Anti-HBc IgM, Anti-HBc IgG. • HBeAg, Anti-HBe.
5. HOW TO DETERMINE THE HIGH INFECTIVITY OF HB SERUM? • HBsAg (+), HBeAg (+), Anti-HBc IgM (+). • Detection of viral DNA polymerase (+). • Detection of viral DNA(+).
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6. DESCRIBE THE SHAPE, STRUCTURE AND GENOMIC TYPE OF HBV. • Shape: spherical particle with 42nm in diameter. • Structure: Enveloped virus (nucleocapsid + envelope or double shells + core). • genomic type: DNA virus.
7. DESCRIBE THE IMMUNE PREVENTION MEASURES FOR HBV INFECTION. • Passive immunization: injection of hyperimmune hepatitis B immunoglobulin (HBIG, anti-HBs) for emergency. • Active immunization: inoculate vaccine(blood source HBV vaccine, gene-engineering vaccine,HBsAg).
HEPATITIS C VIRUS QUESTIONS 1. DESCRIBE MAIN FEATURES OF HCV ENVELOPE PROTEINS AND DISEASE TYPE OF HCV INFECTION. • Protein: E1 and E2 of HCV are the most variable proteins in the antigenicity. • Infection: HCV likely causes chronic hepatitis.
2. STATE THE RELATIONSHIP BETWEEN HBV AND HDV. • Feature: HDV is a defective virus. HBV is it’s helper virus. • Infection: coinfection and superinfection may increase the risk of fulminant hepatitis.
3. WHAT IS CO-INFECTION OF HBV AND HDV? • Infection: occurs when a person becomes simultaneously infected with HBV and HDV. • Consequence: may increase the risk of fulminant hepatitis.
4. WHAT IS HDV SUPERINFECTION? • Infection: occurs in persons with an existing hepatitis B infection. • Consequence: may develop chronic infection and fulminant hepatitis.
5. DESCRIBE TRANSMISSION WAY AND PROGNOSIS OF HEV. • transmission way: Fecal-oral route. • Prognosis: Causing acute hepatitis E, no chronic hepatitis.
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35. Respiratory viruses REFERENCE
INFLUENZA VIRUSES
Section 1
Name :: Influenza virus Disease caused :: Influenza Special characteristics :: Enveloped virus with a helical nucleocapsid and segmented,single-stranded RNA of negative polarity. RNA polymerase in virion. The two major antigens are the hemagglutinin (HA) and the neuraminidase (NA) on separate surface spikes. Antigenic shift in these proteins as a result of reassortment of RNA segments accounts for the epidemics of influenza caused by influenza A virus. Influenza A viruses of animals are the source of the new RNA segments. Antigenic drift due to mutations also contributes. The virus has many serotypes because of these antigenic shifts and drifts. The antigenicity of the internal nucleocapsid protein determines whether the virus is an A, B, or C influenza virus. Transmission :: Respiratory droplets from human to human. H5N1 strains transmitted from birds to humans. Pathogenesis :: Infection is limited primarily to the epithelium of the respiratory tract. Laboratory diagnosis :: A rapid ELISA test to detect influenza viral antigen in respiratory secretions is often used. Virus grows in cell culture and embryonated eggs and can be detected by hemadsorption or hemagglutination. It is identified by hemagglutination inhibition or complement fixation. A fourfold or greater antibody titer rise in convalescent-phase serum is diagnostic. Treatment :: The neuraminidase inhibitor, oseltamivir (Tamiflu), is the drug of choice. Zanamivir, another neuraminidase inhibitor, is also available. Amantadine and rimantadine are no longer used due to widespread resistance. Prevention :: Two types of vaccines are available: (1) a killed (subunit) vaccine containing purified HA and NA; and (2) a vaccine containing a live, temperaturesensitive mutant of influenza virus. The virus in the live vaccine replicates in cool nasal passages, where it induces secretory IgA, but not in warm lower respiratory tract. Both vaccines contain the strains of influenza A and B virus currently causing disease. The killed vaccine is not a good immunogen and must be given annually. The vaccine against “standard” influenza contains either two A strains (H1N1 and H3N2) and one B strain or those two A strains and two B strains. The vaccine against “swine” influenza contains only the novel H1N1 strain of swine origin. Most of these vaccines are made in eggs, so anyone who has had a severe anaphylactic response to egg proteins should not receive the egg-derived vaccine. In 2013, a vaccine not made in eggs became available. Oseltamivir (Tamiflu) can be used for prophylaxis in unimmunized people who have been exposed.
PARAMYXOVIRIDAE
Section 2
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MUMPS VIRUS Name :: Mumps virus Disease caused :: MUMPS. Sterility due to bilateral orchitis is a rare complication Special characteristics :: Enveloped virus with a helical nucleocapsid and one piece of single-stranded, negative-polarity RNA. RNA polymerase in virion. It has a single serotype. Transmission :: Respiratory droplets. Pathogenesis :: The initial site of infection is the upper respiratory tract. The virus spreads to local lymph nodes and then via the bloodstream to other organs, especially the parotid glands, testes, ovaries, meninges, and pancreas. Laboratory diagnosis :: The virus can be isolated in cell culture and detected by hemadsorption. Diagnosis can also be made serologically. PCR assay is available. Treatment :: No antiviral therapy is available. Prevention :: Vaccine contains live, attenuated virus. Usually given in combination with measles and rubella vaccines.
OTHER RESPIRATORY VIRUS
Section 3
RUBELLA VIRUS Name :: Rubella virus Disease caused :: RUBELLA. Congenital rubella syndrome is characterized by congenital malformations, especially affecting the cardiovascular and central nervous systems, and by prolonged virus excretion. The incidence of congenital rubella has been greatly reduced by the widespread use of the vaccine. Special characteristics :: Enveloped virus with an icosahedral nucleocapsid one piece of single-stranded positive-polarity RNA. No polymerase in virion. It has a single serotype. Transmission :: Respiratory droplets and across the placenta from mother to fetus. Pathogenesis :: The initial site of infection is the nasopharynx, from which it spreads to local lymph nodes. It then disseminates to the skin via the bloodstream. The rash is attributed to both viral replication and immune injury. During maternal infection, the virus replicates in the placenta and then spreads to fetal tissue. PAGE 105
If infection occurs during the first trimester, a high frequency of congenital malformations occurs. Maternal antibody protects against fetal infection. Laboratory diagnosis :: Virus is detected by PCR assay. To determine whether an adult woman is immune, a single serum specimen to detect IgG antibody in the hemagglutination inhibition test is used. To detect whether recent infection has occurred, either a single serum specimen for IgM antibody or a set of acute-and convalescent-phase sera for IgG antibody can be used. Treatment :: No antiviral therapy is available. Prevention :: Vaccine contains live, attenuated virus. Usually given in combination with measles and mumps vaccine. CORONAVIRUSES Name :: Coronavirus Disease caused :: COMMON COLD and SARS (severe acute respiratory syndrome) Special characteristics :: Enveloped virus with helical nucleocapsid and one piece of single-stranded, positive-polarity RNA. No virion polymerase. There are two serotypes. Transmission :: Respiratory droplets. Animal coronaviruses may be the source of human infection. Pathogenesis :: Infection is typically limited to the mucosal cells of the respiratory tract. At least 50% of infections are asymptomatic. Immunity is brief and reinfection occurs Laboratory diagnosis :: The diagnosis primarily a clinical one. Antibody-based and PCR-based tests are available but not often done. Treatment :: None Prevention :: No vaccine or drug available
SARS
ADENOVIRUS Name :: Adenovirus Disease caused :: Upper and lower tract respiratory disease, especially pharyngitis and pneumonia. Also conjunctivitis (pink-eye). Enteric strains cause diarrhea. Some strains cause sarcomas in certain animals but not humans. Special characteristics ::
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Nonenveloped virus with icosahedral nucleocapsid and linear double-stranded DNA. No virion polymerase. There are 41 serotypes, some associated with specific diseases. Transmission :: Respiratory droplet primarily; iatrogenic transmission in eye disease; fecal–oral transmission with enteric strains. Pathogenesis :: Virus preferentially infects epithelium of respiratory tract and eyes. After acute infection, persistent, low-grade virus production without symptoms can occur in the pharynx. Laboratory diagnosis :: Virus causes CPE in cell culture and can be identified by fluorescent antibody or complement fixation test. Antibody titer rise in convalescent phase serum is diagnostic. Treatment :: None Prevention :: Live vaccine against types 3, 4, and 7 is used in the military to prevent pneumonia. RHINOVIRUSES Name :: Rhinoviruses Disease caused :: COMMON COLD Special characteristics :: Naked nucleocapsid viruses with single-stranded, Positive polarity RNA. No virion polymerase. There are more than 100 serotypes, which explains why the common cold is so common. Rhinoviruses are destroyed by stomach acid and therefore do not replicate in the GI tract, in contrast to other picornaviruses such as poliovirus, Coxsackie virus, and echovirus, which are resistant to stomach acid. Transmission :: Aerosol droplets and hand-to-nose contact Pathogenesis :: Infection is limited to the mucosa of the upper respiratory tract and conjunctiva. The virus replicates best at the low temperatures of the nose and less well at 37°C, which explains its failure to infect the lower respiratory tract. Laboratory diagnosis :: Laboratory tests are rarely used clinically. The virus can be recovered from nose or throat washings by growth in cell culture. Serologic tests are not useful. Treatment :: No antiviral therapy is available Prevention :: No vaccine is available because there are too many serotypes
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RESPIRATORY VIRUSES RNA Virus
Orthomyxoviridae
Influenza Virus
Paramyxoviridae
Respiratory syncytial virus
Measles Virus
Parainfluenza Virus
Mumps Virus
DNA Virus
Togaviridae
Rubella Virus
Picornaviridae
Rhinovirus
Coronaviridae
Coronavirus (SARS-CoV)
Reoviridae
Reovirus
Adenoviridae
Adenovirus
I. INFLUENZA VIRUS Orthomyxovirdae 3 types: A, B, C enveloped viruses with a segmented –ssRNA
Influenza – ‘flu’ A. BIOLOGICAL PROPERTIES 1.Shape and Size pleomorphic spherical/ovoid :: 80~120nm in diameter
Filamentous :: ~ 4μm in length
2,Structure Nucleocapsid -ssRNA, segmented (8 for types A, B; 7 for type C) Nucleoprotein (NP) RNA polymerases PA, PB1, PB2 Envelope Inner layer: M1, M2 protein Outer layer: lipid bilayer Hemagglutinin (HA) Neuraminidase (NA)
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HA pillar-like, trimer function:
hemagglutinate erythrocytes;
promote attachment and penetration;
antigenicity: HA-Ab
inhibit hemagglutination
neutralize virus infectivity
NA mushroom-like, tetramer function
facilitate release and spread of viruses;
Antigenicity Anti-NA antibody can prevent release of progeny virus and limit spread of infection.
3. Typing and Variation Typing:
Based on NP, M1, and M2: type A, B, C; Based on HA and NA: many subtypes in type A; 16 known HA subtypes: H1-H16 Avian (Birds) 9 known NA subtypes: N1-N9 Human H1-H3, H5, N1-N2
No subtypes in influenza type B, type C.
4. Resistance Sensitivity: Heat, acid, ether, formalin, UV, etc. Resistance: low temperature;
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Pathogenicity Source of infection :: patients, infected animals Route of transmission :: via aerosols or droplets Pathogenesis a. Influenza (flu) o 1-4 days incubation period o The classic “flu syndrome” occurs early. Later, pneumonia may result from bacterial pathogenesis, viral pathogenesis, or immunopathogenesis.
Transmission •Aerosol
Infection •Epithelial Cells
Replication cycle •4 -6 hours
Cell death •Necrosis,apoptosis
Incubation period •18 - 72 hours
PBMC •non- productive
b. Complications o pneumonia o Reye’s syndrome [Syndrome is a disease which affects all organs of the body, but most lethally the liver and the brain.] 3. Immunity :: Short, Re-infection 4.Treatment and Prevention Common prevention Anti-viral drugs: AMANTADINE, RIMAMTADINE ZANAMIVIR and TAMIFLU Vaccines: trivalent vaccine killed influenza vaccine (including H1N1, H3N2, type B); HA-NA subunit vaccine;
PPT QUESTIONS
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Concepts
Antigenic Drift :: minor antigenic changes of HA and NA due to point mutations, belong to quantitative changes, cause annual epidemics of influenza viruses.
Antigenic Shift :: major antigenic changes of HA and NA due to genetic reassortment between human and animal influenza viruses, belong to qualitative changes, result in new subtype and may cause periodic pandemics.
Reassortment :: The phenomenon which segmented genomes of virus (eg. influenza virus) reassort in doubly infected host cells.
SSPE :: (subacute sclerosing panencephalitis)
Questions 1. Why is influenza so difficult to control?
2. List the main members of respiratory viruses and the diseases they cause.
Influenza virus Respiratory syncytial virus Parainfluenza virus Rubella Virus Rhinovirus Coronavirus (SAR-CoV) Reovirus Adenovirus
3. How would measles and mumps be controlled?
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II. PARAMYXOVIRIDAE Including the following three genera GENUS Morbillivirus Paramyxovirus Pneumovirus
HUMAN PATHOGEN Measles Virus Mumps Virus Parainfluenza virus 1 to 4 Respiratory Syncytial Virus (RSV)
Measles virus a potentially serious generalized infection characterized by a maculopapular rash (rubeola) Parainfluenza viruses upper and lower respiratory tract infections,primarily in children, including pharyngitis, croup, bronchitis, bronchiolitis, and pneumonia Mumps virus a systemic infection –parotitis (the most prominent clinical manifestation) RSV o upper and lower respiratory tract infections in children and adults o Life threatening pneumonia in infants
Measles and mumps virus o Only one serotype COMMON PROPERTIES
o Size: 150~300nm in diameter. o Shape: spherical or pleomorphic. o Structure: enveloped; -ssRNA , nonsegmented; genetically stable o Spikes: fusion protein;attachment protein
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36. Enteroviruses REFERENCE
POLIOMYELITIS VIRUS Name :: Poliovirus Disease caused :: Paralytic poliomyelitis and aseptic meningitis. Poliomyelitis has been eradicated in the Western Hemisphere and in many other countries. Special characteristics ::
Naked nucleocapsid virus with single-stranded, positive-polarity RNA. Genome RNA acts as mRNA and is translated into one large polypeptide, which is cleaved by virus-encoded protease to form functional viral proteins. No virion polymerase. There are three serotypes. Transmission :: Fecal oral route. Human are the natural reservoir. Pathogenesis :: The virus replicates in the pharynx and the GI tract. It can spread to the local lymph nodes and then through the bloodstream to the central nervous system. Most infections are asymptomatic or very mild. Aseptic meningitis is more frequent than paralytic polio. Paralysis is the result of death of motor neurons, especially anterior horn cells in the spinal cord. Pathogenesis of postpolio syndrome is unknown. Laboratory diagnosis :: Recovery of the virus from spinal fluid indicates infection of the central nervous system. Isolation of the virus from stools indicates infection but not necessarily disease. It can be found in the GI tract of asymptomatic carriers. The virus can be detected in cell culture by CPE and identified by neutralization with type-specific antiserum. A significant rise in antibody titer in convalescent phase serum is also diagnostic. Treatment :: No antiviral therapy is available. Prevention :: Disease can be prevented by both the inactivated (Salk) vaccine and the live, attenuated (Sabin) vaccine; both induce humoral antibody that neutralizes the virus in the bloodstream. However, only the oral vaccine induces intestinal IgA, which interrupts the chain of transmission by preventing GI tract infection. For that reason and because it induces immunity of longer duration and is orally administered rather than injected, the Sabin vaccine has been the preferred vaccine for many years. However, there have been a few vaccine-associated cases of paralytic polio caused by poliovirus in the vaccine that reverted to virulence. In view of this, the current recommendation in the United States is to use the killed vaccine.
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OTHER ENTROVIRUSES COXSACKIEVIRUSES Name :: Coxsackie Virus Disease caused :: Aseptic meningitis, herpangina, pleurodynia, myocarditis, pericarditis, and hand, foot, and mouth disease are the most important diseases. Also Coxsackie virus B4 may cause juvenile diabetes, as it will do so in mice. Special characteristics :: Naked nucleocapsid virus with single-stranded, positive-polarity RNA. No virion polymerase. Group A and B viruses are defined by their different pathogenicity in mice. There are multiple serotypes in each group. Transmission :: Fecal-oral route Pathogenesis :: The initial site of infection is the oropharynx, but the main site is the GI tract. The virus spreads through the bloodstream to various organs. Laboratory diagnosis :: The virus can be detected by CPE in cell culture and identified by neutralization. A significant rise in antibody titer in convalescent-phase serum is diagnostic. Treatment :: No antiviral therapy is available Prevention :: No vaccine is available ECHOVIRUSES
NEW ENTEROVIRUS TYPE
TO MASTER 1. The members of enterovirus and disease caused by them. VIRUS FAMILY
SEROTYPES
DISEASE CAUSED BY THEM
1-3
Paralytic poliomyalitis
Coxsackie A
1-22, 24
Herpangina,Hand-foot-and-mouth disease,Viral meningitis
Coxsackie B
1-6
Pleurodynia, Myocardial and pericardial infections, Viral meningitis
1-9, 11-27, 29-34
Viral meningitis
Polio
Echovirus Enteric, cytopathic, human, orphan Hepatitis A Other Enteroviruses
Enterovirus 72 68-71
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2. What are the common properties of Enterovirus COMMON BIOLOGICAL PROPERTIES Size: 24-30nm Shape: spherical Structure: naked virus. Nucleocapsid is icosahedral. Nucleic acid: +ssRNA Replication: multiply in the cytoplasm Resistance resistant -- ether, acid (tolerate pH3-5) sensitive -- drying, heat and UV survive for a long period in water and sewage 3. Master the pathogenesis of Polio virus. Pathogenesis Poliovirus infections 3 types (type 1, 2, 3) type 1 causes most epidemics Progression of poliovirus infection – Types of illness Asymptomatic illness >90% Abortive poliomyelitis about 5% Nonparalytic poliomyelitis 1%2% Paralytic poliomyelitis 0.1%-2.0% -----------------------------------------------------i. Virus is transmitted by fecal oral route through ingestion. ii. The virus multiplies initially in the epithelial cells of the alimentary canal and the lymphatic tissues, from the tonsils to the payer’s patches.
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iii.
iv.
v.
vi. vii. viii. ix. x.
It then spreads to the regional lymph nodes and Multiply in Peyer's enter the blood stream Virus ingested Go to blood stream patches of ileum (M through mouth cells) (Primary viremia) After further multiplication in reticuloendothelial system the virus enters the Multiply in Primary viremia (2-3 blood stream again Blood stream reticuloendothelial days) system (Secondary viremia) and is carried to the Spinal cord and brain Direct Neural transmission 2◦ Viremia then Carried to spinal ord to the CNS occurs under invade CNS and Brain special circumstances. ie, Poliomyelitis following tonsillectomy In the CNS, Virus multiplies selectively in the neurons and destroy them. The earliest change is the degeneration of NISSL’S BODIES. Nuclear changes follows When degeneration become irreversible, Necrotic cell lysis or is phagocytosed by leucocytes or macrophages. Lesion are mostly in the anterior horns of the spinal cord causing flaccid paralysis but the posterior horns and intermediate columns may also be involved to some extend.
OVERVIEW
Enteroviruses are a group of viruses that parasitize the enteric tract and cause diseases. fecal-oral route
- belong to picornaviridae: 6 genera 1. Enteroviruses 2. Rhinoviruses: the common cold 3. Hepatoviruses: Hepatitis A 4. Par-echoviruses 5. Aphthovirus: foot-and-mouth disease viruses 6. Cardiovirus: encephalomyocarditis COMMON BIOLOGICAL PROPERTIES Size: 24-30nm Shape: spherical Structure: naked virus. Nucleocapsid is icosahedral. Nucleic acid: +ssRNA Replication: multiply in the cytoplasm Resistance resistant -- ether, acid (tolerate pH3-5) sensitive -- drying, heat and UV survive for a long period in water and sewage
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PATHOGENICITY Portal of entry Viremia Target tissue Different enteroviruses bind to different target cells CLINICAL INFECTION A. Neurologic infection aseptic meningitis, paralysis, encephalitis B. Cardiac and muscular infection myocarditis, pericarditis C. Infection of skin and mucosa hand- foot-and- mouth disease D. Respiratory infection: common colds E. Alimentary infection: diarrhea in children.
POLIOVIRUS :: paralytic poliomyelitis BIOLOGICAL PROPERTIES
Size: 30nm Structure naked virus. Nucleocapsid is icosahedral capsid Nucleic acid +ssRNA infections RNA - mRNA and polypeptide
PATHOGENESIS Poliovirus infections 3 types (type 1, 2, 3) type 1 causes most epidemics Progression of poliovirus infection – Types of illness Asymptomatic illness >90% Abortive poliomyelitis about 5% Nonparalytic poliomyelitis 1%-2% Paralytic poliomyelitis 0.1%-2.0%
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CLINICAL MANIFESTATION 1. Abortive Poliomyelitis o In about 5% patients, a non specific influenza-like syndrome occurs 1-2 weeks after infection. o Fever, malaise, anorexia and headache are prominent features o Sore throat and abdominal or muscular pain. o Vomiting occurs irregularly o Illness short lived, upto 2-3 days. Recovery is complete and no neurological signs. 2. Non Paralytic Poliomyelitis o In about 1% patients, abortive type with aspectic meningitis such as neck rigidity, +ve Kernig’s sign and Brudzinski’s sign. o Manifestation disappear 1-2 days and leave no paralytic manifestation. 3. Paralytic Poliomyelitis o Occurs 0.5% - 1% of all cases. o Due to invasion of the motor nerves, which are responsible for movement of the muscles. o Viral invasion causes inflammation, and then destructions of these nerves. o Divided into 3 types :: 1. Spinal Poliomyelitis Muscles affected are :: lower limbs (quadriceps, harmstrings, anterior tibial and peroneal muscle) 2. Bulbar Poliomyelitis 3. Encephalitic Poliomyelitis PREVENTION Poliovirus vaccines 1960 1. SABIN (live attenuated virus) vaccine OPV (oral polio vaccine) - Albert Sabin 2. SALK (killed virus) vaccine IPV (inactivated polio vaccine) - Jonas Salk
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Property
SABIN VACCINE
SALK VACCINE
OPV (Oral Poliovirus Vaccine)
IPV (Inactivated Poliovirus Vaccine)
Produce local immunity through induction of an IgA response as well as systemic immunity
Produce serum Ab only; does not induce local gut immunity. Thus, do not prevent local infection of gut
Rarely cause paralytic poliomyelitis, around 1 in 3 million doses
Will prevent paralytic poliomyelitis since viremia is essential cause pathogenesis of the disease
Satisfactory
Satisfactory
3 doses at 6-8 weeks interval
Primary vaccination : 2-3 doses at 4-6 weeks intervals, boosters doses
Oral
Every 3-5 years ; injection
More
Less
Induce both local and systemic immunity, Systemic Ab
No local immunity
Lifelong
May need to be maintained by booster doses periodically
Spread naturally to unvaccinated individuals by fecal-oral spread
No spread
Less stable and more difficult for preservation and transport in tropic area
Stable; preservation and transportation are convenient
Safety Efficiency
Cost Nature of immunity Duration of immunity Spread of vaccine Stability
GASTROENTERITIS REALTED VIRUSES Human Rotavirus (HRV) ď&#x192;&#x2DC; BIOLOGICAL PROPERTIES o Size: 60-80nm o Shape: icosahedral nucleocapsid o Structure: naked virus o Capsid: Possess two concentric capsid shells, icosahedral o Core: Possess a genome containing 11 segments of double-stranded RNAs ď&#x192;&#x2DC; PATHOGENESIS o one of the most common causes of infantile diarrhea worldwide. o High risk people :: children 6 months - 2 years old o Route of transmission :: fecal-oral route o Virus infects columnar epithelial cells covering the villi of the small intestine o multiply in the cytoplasm causes cell lysis and abnormal function o damage their transport mechanisms to interrupt sodium and water absorption
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o infection prevents the absorption of water o causing a net secretion of water and loss of ions, which together results in a watery diarrhea and vomiting→ dehydration, acidosis, shock and death o Diarrhea watery (no blood or leukocytes), lasting 39 days o Many cases and outbreaks are nosocomial [originating in a hospital.] o Incubation period 1-4 days o Contagious Period - Before onset of diarrhea to a few days after end of diarrhea o Spread via fecal-oral route through fomites DIAGNOSIS Rapid diagnosis - antigen detection in stool by ELISA Electron microscopy TREATMENT Supportive - rehydration (oral / intravenous) Antiviral agents not known to be effective Prevention of spread Handwashing with good technique Disinfection of surfaces, toilets, toys Vaccine Rotashield was first licensed for use in infants in 1998.
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37. Herpesviruses REFERENCE
HERPES SIMLEX VIRUS HERPES SIMPLEX VIRUS (Type I) Name :: Herpes Simplex Virus Type 1 Disease caused :: Herpes labialis (fever blisters or cold sores), keratitis, encephalitis. Type :: Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA. Special characteristics :: No virion polymerase. One serotype; cross-reaction with herpes simplex virus (HSV) type 2 occurs. HSV-1 can be distinguished from HSV-2 by using monoclonal antibody against glycoprotein G. No herpes group–specific antigen. Transmission :: By saliva or direct contact with virus from the vesicle. Pathogenesis :: Initial vesicular lesions occur in the mouth or on the face. The virus then travels up the axon and becomes latent in sensory (trigeminal) ganglia. Recurrences occur in skin innervated by affected sensory nerve and are induced by fever, sunlight, stress, etc. Dissemination to internal organs occurs in patients with depressed cellmediated immunity with life-threatening consequences. HSV-1 encephalitis often affects the temporal lobe. Laboratory diagnosis :: Virus causes cytopathic effect (CPE) in cell culture. It is identified by antibody neutralization or fluorescent antibody test. Tzanck smear of cells from the base of the vesicle reveals multinucleated giant cells with intranuclear inclusions. These giant cells are not specific for HSV-1; they are seen in the vesicular lesions caused by HSV-2 and varicella-zoster virus as well. A rise in antibody titer can be used to diagnose a primary infection but not recurrences. HSV encephalitis can be diagnosed using a PCR assay to detect HSV-1 DNA in spinal fluid. Treatment :: Acyclovir for encephalitis and disseminated disease. Acyclovir has no effect on the latent state of the virus. Trifluridine or acyclovir for keratitis. Primary infections and localized recurrences are self-limited. Prevention :: Recurrences can be prevented by avoiding the specific inciting agent such as intense sunlight. Acyclovir, valacyclovir, or famciclovir is used to reduce recurrences. No vaccine is available.
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HERPES SIMPLEX VIRUS (Type II) Name :: Herpes Simplex Virus Type 2 Disease caused :: HERPES GENITALIS, ASPECTIC MENINGITIS and NEONATAL INFECTION Special characteristics :: Enveloped virus with icosahedral nucleocapsid and Linear double-stranded DNA. No virion polymerase. One serotype; cross-reaction with HSV-1 occurs. HSV-2 can be distinguished from HSV-1 by using monoclonal antibody against glycoprotein G. No herpes group–specific antigen. Transmission :: Sexual contact in adults and during passage through the birth canal in neonates. Pathogenesis :: Initial vesicular lesions occur on genitals. The virus then travels up the axon and becomes latent in sensory (lumbar or sacral) ganglion cells. Recurrences are less severe than the primary infection. HSV-2 infections in neonate can be lifethreatening because neonates have reduced cellmediated immunity. Asymptomatic shedding of HSV-2 in the female genital tract is an important contributing factor to neonatal infections. Laboratory diagnosis :: Virus causes CPE in cell culture. Identify by antibody neutralization or fluorescent antibody test. Tzanck smear reveals multinucleated giant cells but is not specific for HSV-2. A rise in antibody titer can be used to diagnose a primary infection but not recurrences. Treatment :: Acyclovir is useful in the treatment of primary and recurrent genital infections as well as neonatal infections. It has no effect on the latent state. Prevention :: Primary disease can be prevented by protection from exposure to vesicular lesions. Recurrences can be reduced by the long-term use of oral acyclovir, valacyclovir, or famciclovir. Neonatal infection can be prevented by delivering the child by cesarean section if the mother has visible vesicular lesions in the birth canal. There is no vaccine.
VARICELLA-ZOSTER VIRUS
Section 2
Name :: Varicella-Zoster Virus Disease caused :: VARICELLA (Chickenpox) in Children ; ZOSTER (shingles) in adults. Type :: Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA
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Special characteristics :: No virion polymerase. One serotype Transmission :: Varicella is transmitted primarily by respiratory droplets. Zoster is not transmitted; it is caused by a reactivation of latent virus. Pathogenesis :: Initial infection is in the oropharynx. It spreads via the blood to the internal organs such as the liver and then to the skin. After the acute episode of varicella, the virus remains latent in the sensory ganglia and can reactivate to cause zoster years later, especially in older and immunocompromised individuals. Laboratory diagnosis :: Virus causes CPE in cell culture and can be identified by fluorescent antibody test. Multinucleated giant cells seen in smears from the base of the vesicle. Intranuclear inclusions seen in infected cells. A fourfold or greater rise in antibody titer in convalescent-phase serum is diagnostic. Treatment :: No antiviral therapy is indicated for varicella or zoster in the immunocompetent patient. In the immunocompromised patient, acyclovir can prevent dissemination. Prevention :: Both the varicella vaccine and the zoster vaccine contain live, attenuated varicellazoster virus. Immunocompromised patients exposed to the virus should receive passive immunization with varicella-zoster immune globulin (VZIG) and acyclovir to prevent disseminated disease.
CYTOMEGALOVIRUS Name :: Cytomegalovirus Disease caused :: Congenital abnormalities. Cytomegalic inclusion body disease in infants. Mononucleosis in transfusion recipients. Pneumonia and hepatitis in immunocompromised patients. Retinitis and enteritis, especially in AIDS patients. Type :: Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA. Special characteristics :: No virion polymerase. One serotype. Transmission :: Virus is found in many human body fluids, including blood, saliva,semen, cervical mucus, breast milk, and urine. It is transmitted via these fluids,across the placenta, or by organ transplantation. Pathogenesis :: Initial infection usually in the oropharynx. In fetal infections, the virus spreads to many organs (e.g., central nervous system and kidneys). In adults, lymphocytes are frequently involved.
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A latent state occurs in monocytes. Disseminated infection in immunocompromised patients can result from either a primary infection or reactivation of a latent infection Laboratory diagnosis :: The virus causes CPE in cell culture and can be identified by fluorescent antibody test. “Owl’s eye” nuclear inclusions are seen. A fourfold or greater rise in antibody titer in convalescent-phase serum is diagnostic. Treatment :: Ganciclovir is used to treat pneumonia and retinitis. Acyclovir is ineffective. Prevention :: No vaccine is available. Ganciclovir suppresses retinitis. Do not transfuse CMV antibody-positive blood into newborns or antibody-negative immunocompromised patients
EPSTEIN-BARR VIRUS Name :: Epstein-Barr Virus Disease caused :: Infectious mononucleosis; associated with Burkitt’s lymphoma in East African children. Type :: Enveloped virus with icosahedral nucleocapsid and linear double-stranded DNA. Special characteristics :: No virion polymerase. One serotype. Transmission :: Virus found in human oropharynx and B lymphocytes. It is transmitted primarily by saliva. Pathogenesis :: In infectious mononucleosis, infection begins in the pharyngeal epithelium, spreads to the cervical lymph nodes, and then travels via the blood to the liver and spleen. EBV establishes latency in B lymphocytes. In Burkitt’s lymphoma, oncogenesis is a function of the translocation of the c-myc oncogene to a site adjacent to an immunoglobulin gene promoter. This enhances synthesis of the c-mycprotein, a potent oncoprotein. Laboratory diagnosis :: The virus is rarely isolated. In infectious mononucleosis, lymphocytosis, including atypical lymphocytes, occurs. Heterophil antibody is typically positive (Monospot test). Heterophil antibody agglutinates sheep or horse red blood cells. A significant rise in EBV-specific antibody to viral capsid antigen is diagnostic. Treatment :: No effective drug is available for infectious mononucleosis Prevention :: There is no drug or vaccine.
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HUMAN HERPESVIRUS 6
Causes Kaposi’s sarcoma, especially in AIDS patients. Transmitted sexually. Diagnosis made by pathologic examination of lesion biopsy. See spindle cells and extravasated red blood cells. Purple color of lesions due to collections of venous blood. No specific antiviral treatment and no vaccine.
38. Retroviruses and Cancer Associated Viruses REFERENCE
HUMAN IMMUNODEFEICIENCY VIRUS
Section 1
Name :: Human Immunodeficiency Virus Disease caused :: Acquired Immuno-Deficiency Syndrome (AIDS) Special characteristics :: Enveloped virus with two copies (diploid) of a single-stranded, positive-polarity RNA genome. RNA-dependent DNA polymerase (reverse transcriptase) makes a DNA copy of the genome, which integrates into host cell DNA. Precursor polypeptides must be cleaved by virus–encoded protease to produce functional viral proteins. The tat gene encodes a protein that activates viral transcription. Antigenicity of the gp120 protein changes rapidly; therefore, there are many serotypes. Transmission :: Transfer of body fluids (e.g., blood and semen). Also trans placental and perinatal transmission. Pathogenesis :: Two receptors are required for HIV to enter cells. One receptor is CD4 protein found primarily on helper T cells. HIV infects and kills helper T cells, which predisposes to opportunistic infections. Other cells bearing CD4 proteins on the surface (e.g., astrocytes) are infected also. The other receptor for HIV is a chemokine receptor such as CCR5. The NEF protein is an important virulence factor. It reduces class I MHC) protein synthesis, thereby reducing the ability of cytotoxic T cells to kill HIV-infected cells. Cytotoxic T cells are the main host defense against HIV. Laboratory diagnosis :: HIV can be isolated from blood or semen, but this procedure is not routinely available. Diagnosis is usually made by detecting antibody with ELISA as screening test and Western blot as confirmatory test. Determine the “viral load” (i.e., the amount of HIV RNA in the plasma) using PCR based assays. A high viral load predicts a more rapid progression to AIDS than a low viral load. PCR-based assays can also detect viral RNA in infected cells, which is useful to detect early infections before antibody is detectable Treatment ::
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Highly active antiretroviral therapy (HAART) consists of several drugs combined into various regimens. Each regimen has emtricitabine and tenofovir, to which efavirenz, raltegravir, or a combination of two protease inhibitors (either ritonavir plus atazanavir or ritonavir plus darunavir) is added. Clinical improvement occurs, but the virus persists. Nucleoside analogues, such as zidovudine, lamivudine, emtricitabine, tenofovir, and others inhibit HIV replication by inhibiting reverse transcriptase.Nonnucleoside inhibitors of reverse transcriptase, such as efavirenz, nevirapine, and others, are used also. Protease inhibitors (e.g., indinavir, ritonavir, and others) prevent cleavage of precursor polypeptides. Integrase inhibitors, such as raltegravir, dolutegravir, and elvitegravir, block the integration of HIV DNA into host cell DNA by inhibiting the integrase of HIV. Enfuvirtide, a “fusion inhibitor” that blocks entry of HIV, and maraviroc, which inhibits binding of the gp120 envelope protein of HIV to the cell co-receptor CCR-5, are also useful. Treatment of the opportunistic infection depends on the organism. Prevention ::
Screening of blood prior to transfusion for the presence of antibody. “Safe sex,” including the use of condoms. Zidovudine (ZDV, AZT) with or without a protease inhibitor should be given to HIV-infected mothers and their newborns. ZDV, lamivudine and a protease inhibitor should be given after a needle-stick injury. A combination of tenofovir and emtricitabine can be used for preexposure prophylaxis in individuals at high risk of infection. There is no vaccine.
Association of viruses with human cancers1 Virus family
Virus
Human Cancer
PAPILLOMAVIRIDAE
Human papillomaviruses
Genital tumors Squamous cell carcinomas Oropharyngeal carcinoma
EB Virus
Nasopharyngeal carcinoma African Burkitt’s lymphoma B cell lymphoma
Hepatitis B Virus
Hepatocellular carcinoma
HTL Virus Human immune-deficiency virus Hepatitis C Virus
Adult T cell leukemia AIDS-related malignancies Hepatocellular carcinoma
HERPESVIRIDAE
HEPADNAVIRIDAE RETROVIRIDAE FLAVIVIRIDAE
1 Candidate human tumor viruses include human herpesvirus 8, additional tyes of papillomaviruses and polyomaviruses SV40, JC and BK
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39. Encephalitis Viruses REFERENCE
JAPANESE ENCEPHALITIS VIRUS
Section 1
Member of the flavivirus family. Causes outbreaks of encephalitis in Asian countries. Transmitted to humans by mosquitoes from the reservoir hosts, birds and pigs. No antiviral therapy. An inactivated vaccine is available.
FOREST ENCEPHALITIS VIRUSES
Section 2
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40. Hemorrhagic Fever Viruses REFERENCE
HANTAVIRUSES
Section 1
Member of the bunyavirus family. Causes hantavirus pulmonary syndrome. Sin Nombre virus (SNV) is a robovirus (i.e., it is rodent-borne). Deer mice are the reservoir, and the virus is acquired by inhalation of dried urine and feces. Diagnosis is made by detecting viral RNA in lung tissue or by serologic tests.
No antiviral therapy and no vaccine.
XINJIANG HEMORRHAGIC FEVER VIRUS
Section 2
DENGUE VIRUS
Section 3
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41. Other Important Viruses REFERENCE
POXVIRUSES
Section 1
RABIES VIRUS
Section 2
Name :: Rabies virus Disease caused :: RABIES is an encephalitis Special characteristics :: Bullet-shaped enveloped virus with a helical nucleocapsid and one piece of single-stranded, negative-polarity RNA. RNA polymerase in virion. The virus has a single serotype. Transmission :: Main reservoir is wild animals such as skunks, raccoons, and bats. Transmission to humans is usually by animal bite, but the virus is also transmitted by aerosols of bat saliva. In the United States, dogs are infrequently involved because canine immunization is so common, but in developing countries they are often involved. Pathogenesis :: Viral receptor is the acetylcholine receptor. Replication of virus at the site of the bite, followed by axonal transport up the nerve to the central nervous system. After replicating in the brain, the virus migrates peripherally to the salivary glands, where it enters the saliva. When the animal is in the agitated state as a result of encephalitis, virus in the saliva can be transmitted via a bite. Laboratory diagnosis :: Tissue can be stained with fluorescent antibody or with various dyes to detect cytoplasmic inclusions called Negri bodies. The virus can be grown in cell culture, but the process takes too long to be useful in determining whether a person should receive the vaccine. Serologic testing is useful only to make the diagnosis in the clinically ill patient. Antibody does not form quickly enough to help in the decision whether or not to immunize the person who has been bitten. Serologic testing is also used to evaluate the antibody response to the vaccine given before exposure to those in high-risk occupations. PCR assay can provide rapid diagnosis. Treatment :: No antiviral therapy is available Prevention :: Pre exposure prevention of rabies consists of the vaccine only. Post exposure prevention consists of (1) washing the wound; (2) giving rabies immune globulins (passive immunization), mostly into the wound; (3) giving the inactivated vaccine (active immunization) made in human cell culture.
The decision to give the immune serum and the vaccine depends on the circumstances. Prevention of rabies in dogs and cats by using a killed vaccine has reduced human rabies significantly.
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ACUTE GASTROENTERITIS VIRUSES
Section 3
ROTAVIRUSES
CALICIVIRUSES
ASTROVIRUSES
ADENOVIRUSES
PARVOVIRUSES
Section 4
PRION
Section 5
RABIES VIRUS
rabies is an acute infection of the central nervous system that is almost always fatal. transmitted to humans from the bite of a rabid animal. a major public health problem
Shape: bullet Genome: -ssRNA enveloped virus CPE: Negri body
RESERVOIR Urban forms: Dogs and cats Sylvatic forms: Bats, foxes, raccoons, wolves, skunks, coyotes, mongooses, and biting animals TRANSMISSION By bite or scratch Via saliva Airborne ( bats) NEGRI BODY
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When rabies viruses multiply in CNS cells of susceptible animals or human, they can produce cytoplasmic, acidophilic, round or oval inclusion bodies called Negri body, they can help diagnose rabies. PATHOGENESIS multiplies in muscle enters peripheral nerves at neuromuscular junctions spreads up the nerves to CNS multiplies in the brain and spread through peripheral nerves to the salivary glands and other tissues.
Virus enters via animal bite Virus replicates in muscle at site of bite Virus infects nerve in peripheral nervous system. Moves by retrograde transport
SYMPTOMS Rabies or HYDROphobia Virus replicates in dorsal root o Fever ganglion and travels up spinal cord to brain o Dysphagia [difficulty or discomfort in swallowing] o Altered mental status o Excitement, agitation [a state of anxiety or nervous excitement] Brain infected o Paralysis o Hydrophobia Virus travels from brain via nerves o Hypersalivation to other tissues such as eye, o Nausea, vomiting kidneys, salivary glands o Headache o Malaise [a feeling of general discomfort or uneasiness, of being "out of sorts", often the first indication of an infection or other disease]
LABORATORY DIAGNOSIS • Diseased dog: viral antigen and Negri body in brain tissue. • Patient: IF assay, PCR. CLINICAL FEATURES o Incubation period -10 days to 16 weeks o Symptoms a. Early phase: fever, pain around the site of infection. b. Phase of excitement: lacrimation, pupillary dilation, increased salivation and perspiration, muscle spasm. Slight stimuli may cause spasm. hydrophobia c. Paralytic phase: coma, respiratory and circulation failure, and death. PREVENTION AND CONTROL For individuals bitten by a dog 1. Carefulness of wound all bites should be thoroughly cleaned with soap and water immediately 70% ethanol 2. Passive immunization high titer anti-rabies virus serum - injection. 3. Active immunization
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inactivated vaccines
HUMAN PAPILLOMA VIRUS (HPV) BIOLOGICAL PROPERTIES • naked dsDNA virus with 9 ORF • belongs to Papovaviridae • more than 60 types • artificial cultivation un-successful. TRANSMISSION • contact infection • sexual infection • congenital infection. PATHOGENESIS • Host-specific • Tissue-specific. DISEASE Cutaneous warts Epidermodysplasia verruciformis Mucosal HPV infections Cervical cancer and other cancers: A significant proportion of cancers is associated with HPV infection: 11% of all cancers in women and 2% of all cancers in men. LABORATORY DIAGNOSIS • - Cytology - Histology - Colposcopy in the case of genital HPV infections. - Electron microscopy. • - Immunocytochemistry can detect major capsid protein but are generally group specific not type specific - DNA detection techniques. This is the only way to type HPVs.PCR
PRIONS Different from Virus No dectectable virions in infected tissues No detectable virions in purified infectious material If nucleic acid is present, very small Very resistant
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REACTION TO CHEMICAL AND PHYSICAL AGENTS Resistant to or only partially inactivated by
Inactivated by
1. Folmaldehyde
1. Autoclaving
2. Ethanol
2. 5% sodium hypochloride
3. Glutaraldehyde
3. Sodium hydroxide
4. Ultraviolet and ionizating irradiation
4. Proteases, urea, other protein denaturants
5. Non-ionic detergents . PATHOGENESIS Kuru
CJD(Creutzfeldt Jakob disease)
GSS(Gerstmann Straussler-Scheinker syndrome)
FFI(Fetal familial insomnia)
Scrapie(sheep and goats)
Bovine spongiform encephalopathy
Transmissible mink encephalopathy
Chronic wasting disease of mule deer
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Viruses Important Questions TERM EXPLANATION 1. HA HA – Hemagglutinin Piller like, trimer, glycoprotein on influenza virus Promote attachment and penetration Hemagglutinate erythrocytes
2. GENETIC REASSORTMENT The phenomenon which segmented genomes of virus (eg. influenza virus) reassort in doubly infected host cells.
3. SABIN VACCINE > Sabin (live attenuated virus) vaccine OPV (oral polio vaccine) > Nature of immunity :: Induce both local and systemic immunity > Duration of immunity :: lifelong > Dosage :: 3 doses at 6 – 8 weeks interval by oral
4. HEMORRHAGIC FEVER > Are a group of viruses that can cause viral hemorrhagic fever (VHF) > A joint name of some diseases that are characterized by Fever, Hemorrhagic manifestations and damage of certain tissue or organ
5. PRION Small Filterable Need host cells No machinery for energy generation of protein synthesis Common disease caused by Prion is BSE. Are infectious particle without nucleic acid.
6. RUBELLA CONGENITAL SYNDROME Congenital rubella syndrome: Infection during early pregnancy May result in serious abnormalities of fetus (the earlier in pregnancy infection occurs, the greater the damage to fetus)
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7. ANTIGENIC SHIFT > major antigenic changes of HA and NA due to genetic reassortment between human and animal influenza viruses > belong to qualitative changes > result in new subtype > may cause periodic pandemics.
8. ANTIGENIC DRIFT > minor antigenic changes of HA and NA due to point mutations > belong to quantitative changes > cause annual epidemics of influenza viruses.
9. RUBELLA Rubella: German measles; 3-day measles an acute febrile illness Characterized by a rash and lymphadenopathy Affects children and young adults
10. HEMORRHAGIC FEVER VIRUSES > Are a group of viruses that can cause viral hemorrhagic fever (VHF) > A joint name of some diseases that are characterized by Fever, Hemorrhagic manifestations and damage of certain tissue or organ
11. PRION DISEASE Prion diseases belong to group of progressive conditions that affect the nervous system in humans and animals. In people, prion diseases impair brain function ; o causing memory changes o personality changes o a decline in intellectual function (dementia) o problems with movement that worsen over time. The signs and symptoms of these conditions typically begin in adulthood, and these disorders lead to death within a few months to several years
12. HHV are a group of large DNA viruses that share common virion morphology a basic mode of replication the capacity to establish latent and recurrent infections
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13. REPIRATORY VIRUS Respiratory virus are DNA or RNA virus that cause disease in respiratory system. And major causes of acute respiratory disease (ARD) including :: Influenza Viruses Para-influenza virus Rhinoviruses Adenoviruses Respiratory syncytial virus (RSV) Respiratory coronaviruses
14. POLIOMYELITIS Etiologic agent :: POLIOVIRUS Also names as Infantile paralysis It’s an acute infectious disease that is in serious form affects CNS The destruction of motor neurons in the spinal cord results in flaccid paralysis. Prevention :: Salk vaccine (IPV) and Sabin vaccine (OPV)
15. HPV • naked dsDNA virus with 9 ORF • belongs to Papovaviridae • more than 60 types • artificial cultivation un-successful.
SHORT QUESTIONS 1. Describe the typical course of untreated HIV infection. Stages include primary infection
dissemination of virus to lymphoid organs
clinical latency
elevated HIV expression
clinical disease
DEATH
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2. Please describe 4 types of HHV, transmission route and diseases caused by them? . TRANSMISSION ROUTE DISEASE CAUSED HHV1 (HSV-1) Close contact Oral Ocular lesions Encephalitis HHV2 (HSV-2) Close contact (STD) Genital lesions Neonatal infections HHV3 (VZV) Contact Chickenpox (Primary infection) Respiratory route Shingles (reactivation) HHV4 (EBV) Saliva (kissing disease) Infectious mononucleosis Burkitt’s lymphoma Immunoblastic lymphomas Nasopharyngeal carcinoma Some T – cell tumors HHV5 (CMV) Close contact Mononucleosis Transfusions Severe congenital infection Tissue transplant Infections in Congenital immunocompromised 3. How to prevent rabies via effective preexposure and postexposure prophylaxis? PRE EXPOSURE Vaccination of dogs and cats POST EXPOSURE For individuals bitten by a dog 1. CAREFULNESS OF WOUND all bites should be thoroughly cleaned with soap and water immediately > 70% ethanol 2. PASSIVE IMMUNIZATION high titer anti-rabies virus serum - injection. 3. ACTIVE IMMUNIZATION inactivated vaccines 4. Describe 5 viruses that can cause STD and their characteristic disease. CYTOMEGALOVIRUS Mononucleosis Severe congenital infection Infections in immunocompromised GENITAL WARTS/ Cutaneous warts - Epidermodysplasia verruciformis - Mucosal HPV HUMAN infections - Cervical cancer and other cancers PAPILLOMAVIRUS(HPV) HEPATITIS(B,C & D) Acute viral hepatitis - Fulminant hepatitis - Chronic hepatitis. HERPES(HSV2) Genital lesions Neonatal infections HIV(AIDS) AIDS - Cellular and humoral immunity decrease. Cellular immunity
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HTLV-1 HTLV-2/HUMAN LYMPHOTROPIC VIRUSES
decrease: Lymphocytes number decreases - Inversion of CD4+ / CD8 + cells proportion - proliferative reaction of T cells decrease - Delayed hypersensitivity decrease or disappear. Humoral immunity decrease: In early phase, B cell polyclonal activation causes immunoglobulins increase - In late phase, antibody immune response decreases. [HTLV-1] adult T cell leukemia-lymphomas (ATL) [HTLV-2] hairy cell leukemia
5. Describe 5 viruses that are related to cancer and their transmission. HPV(Human STD Pappiloma Virus) HBV In highly endemic areas, hepatitis B is most commonly spread from mother to child at birth (perinatal transmission) or through transmission (exposure to infected blood), especially from an infected child to an uninfected child first 5 years of life. The development of chronic infection is very common in infants infected from their mothers or before the age of 5 years. HCV Injecting drug use through the sharing of injection equipment; in health care settings due to the reuse or inadequate sterilization of medical equipment, especially syringes and needles; the transfusion of unscreened blood and blood products; HCV can also be transmitted sexually and can be passed from an infected mother to her baby; however these modes of transmission are much less common. EBV (Epstein barr Saliva (Kissing disease) virus) KSHV(Kaposi STD sarcoma Saliva associated herpesvirus) HTLV – 1 By sexual contact Via contaminated blood or blood products From mother to child via breast milk
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LONG QUESTIONS 1. WHY INFLUENZA VIRUS ARE EASY TO CAUSE PANDEMIC? IF HIGHLY PATHOGENIC AVIAN INFLUENZA (CAUSED BY H5N1 VIRUS) CAN TRANSMIT AMONG PEOPLE, WHAT MEASURE SHOULD WE TAKE IN ORDER TO PREVENT INFECTION? It can cause pandemic: (1) Highly Variant: it can go (1) Antigenic drift: minor antigenic changes of HA and NA due to point mutations, belong to quantitative changes, cause annual epidemics of influenza viruses. (2) Antigenic shift: major antigenic changes of HA and NA due to genetic reassortment between human and animal influenza viruses, belong to qualitative changes, result in new subtype and may cause periodic pandemics. (3) Genetic Reassortment: The phenomenon which segmented genomes of virus (eg. influenza virus) reassort in doubly infected host cells. For example, Human H2N2 and Avian H3N8 can result in Human H3N2. (2) Strains can interchange between avians and humans to result in Highly pathogenic Human strains. (3) Source of infection: patients, infected animals. (4) Route of transmission: via aerosols or droplets. (5) Fast pathogenesis: transmission in aerosoles, infection of epithelial cells, replication cycle 4-6 h, cell death by necrosis or apoptosis, incubation, PBMC non-productive. PREVENTION: (1) While investigating new strains, a biological safety cabinet (BSC) helps prevent any airborne virus from escaping the confines of the cabinet and PAPR, which helps filtering the air that she was breathing. (2) Anti-viral drugs: amantadine, rimamtadine; Zanamivir and Tamiflu
(3) Vaccines: trivalent vaccine: killed influenza vaccine (including H1N1, H3N2, type B); HA-NA subunit vaccine; *PANDEMIC – is an epidemic of infectious disease that has spread through human population across a large region.
2. WHERE CAN HSV-1, HSV-2, VZV, EBV AND CMV SEPARATELY KEEP IN LATENT STATE AND WHAT DISEASE CAN BE CAUSED BY THEM? SITE OF LATENCY DISEASE HSV – 1 Neuron Oral (HHV1) Ocular lesions Encephalitis HSV – 2 Neuron Genital lesions (HHV2) Neonatal infections VZV Neuron Chickenpox (Primary infection) (HHV3) Shingles (reactivation) EBV B cell Infectious mononucleosis (HHV4) Burkitt’s lymphoma Immunoblastic lymphomas Nasopharyngeal carcinoma Some T – cell tumors CMV Monocyte Mononucleosis (HHV5) Lymphocyte Severe congenital infection Infections in immunocompromised
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3. WHAT IS AIDS? WHY DOES OPPORTUNISTIC INFECTION EASILY OCCUR IN HIV-INFECTED, ESPECIALLY AIDS PATIENT? <newly added> AIDS â&#x20AC;&#x201C; ACQUIRED IMMUNO DEFICIENCY SYNDROME Acquired immunodeficiency syndrome: a disease in which there is a severe loss of the body's cellular immunity, greatly lowering the resistance to infection and malignancy. HIV is the etiologic agent of AIDS. OPPORTUNISTIC INFECTION EASILY OCCUR IN HIV-INFECTED, ESPECIALLY AIDS PATIENTS AS :: Cellular immunity decrease
1. Lymphocytes number decreases. 2. Inversion of CD4+ / CD8 + cells proportion. 3. Proliferative reaction of T cells decrease. 4. Delayed hypersensitivity decrease or disappear. Humoral immunity decrease
In early phase, B cell polyclonal activation causes immunoglobulins increase. In late phase, antibody immune response decreases.
Due to weak immunity and decreased cellular and humoral immunity, opportunistic infection is easy because of weak immune system allowing the infecting agents to easily continue their path.
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MICROBIOLOGY 2012 BATCH QUESTIONS TERMS 1. Transposon (Tn) 2. SPA (Staphylococcus Protein A) 3. Widal Test 4. Sulfur granule (Actinomycines) 5. Reagin 6. Prion 7. Salk vaccine SHORT & LONG QUESTIONS 1. What are the difference between exotoxin & endotoxin ? 2. What is widal test ? And how to interpret the result ? 3. What is OT test ? Please explain OT results. 4. What is Dane particle ? 5. Describe the typical cause of untreated HIV infection. 6. Why influenza virus are easy to cause pandemic ? 7. Difference between Gram +ve and Gram â&#x20AC;&#x201C;ve bacterial cell wall.
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MICROBIOLOGY 2013 BATCH TERMS (3x10 = 30) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
SEPTICEMIA COLONY STERILIZATION REAGIN SPA OT TEST HEMORRAGIC FEVER VIRUS VIRION ANTIGENIC DRIFT HORIZONTAL TRANSMISSION
SHORT QUESTION (6x8 = 48) 1. DIFFERENCE BETWEEN ENDOTOXIN AND EXOTOXIN. 2. VIRULENCE FACTOR OF S.AUREUS 3. DESCRIBE THE MECHANISM OF GENE TRANSFER AND RECOMBINATION. 4. STAGES OF SYPHILIS. 5. FUNCTION OF NUCLEIC ACID. 6. MECHANISM OF VIRAL INTERFERON. 7. PRE AND POST EXPOSURE OF RABIES PROPHYLAXIS. 8. WIDAL TEST AND ITS RESULT.
LONG QUESTIONS (7+7+8 = 22) 1. DIFFERENCE BETWEEN GRAM + AND GRAM â&#x20AC;&#x201C; CELL WALL 2. WHAT IS AIDS? HOW IT CAUSE INFECTION IN HIV PATIENT 3. WHAT IS DANE PARTICLE ? PREVENTIONOF HBV.
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