Infection
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Overview • Types of Microorganisms • Principles of Infection – – – –
Transmission Host resistance Virulence and pathogenicity Control of transmission and infection
• Development of Infection – Onset and course – Clinical signs and symptoms – Diagnostic tests
• Antimicrobial Drugs www.indiandentalacademy.com
Microbiology • Study of microorganisms – Bacteria, viruses, protozoa, fungi
• Many are prokaryotes – Simple in structure – Complex cell wall
• Many are pathogenic • Vary widely in growth needs – Specific req are basis for lab tests • Grown in petri dish in specific culture medium – Culture contains nutrients for specific microbial group » Need for oxygen, carbon dioxide, pH, temp varies www.indiandentalacademy.com
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Classification of Bacteria • Bacilli – Clostridium tetani
• Spirals – Treponema pallidum
• Cocci – Diplocci – Streptococci – Staphylococci • Staphylococcus aureus www.indiandentalacademy.com
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Bacterial Structure • Rigid cell wall – 2 types • Gram negative • Gram positive
• Cell membrane – Semipermeable – Metabolic processes occur here
• External capsule/slime layer – On some; extra protection, interferes w/ phagocytosis
• Flagellae www.indiandentalacademy.com
Bacterial Structure • Pili or fiimbriae – Usually gram neg; attach bacterium to tissue – Transfer DNA to another bacterium = mutation
• Cytoplasm – Chromosome (long strand of DNA) – Ribosome (RNA) – Plasmids (DNA fragments) • Imp for drug resistance www.indiandentalacademy.com
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Bacterial Structure • Some secrete toxic substances, toxins, enzymes – Toxins • Exotoxins: gram pos; diffuse thru body fluids – Often interfere w/ nerve conduction – Stimulate antibody/antitoxin production
• Endotoxins: gram neg; released after organism dies – Causes fever, weakness, circ problems » Increase cap perm, loss vasc fluid, endotoxic shock
– Enzymes • Damage host cells/tissues • Ex: Hemolysin destroys RBC www.indiandentalacademy.com
Hemolysin and RBC
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Bacterial Structure • Some form spores – Latent form resistant to heat – Survive long time as spore; cannot reproduce in this state – Resume normal state when conditions favorable – Ex: tetanus, botulism
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Tetanus, Botulism Spores
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Bacteria: Reproduction • Duplicate thru binary fission • Generation time: minutes – hours • Limiting factors to growth: – Nutrients, oxygen, effects of increased metabolic wastes, changes in pH and temp www.indiandentalacademy.com
Viruses • Very small intracellular parasite • Obligate • Called virion when outside of cell • Consists of: – Protein coat (capsid) – Core • RNA or DNA www.indiandentalacademy.com
Viruses: Replication • Attach to host cell and inserts genetic material • Viral DNA or RNA takes over cell – Uses host cell to replicate new viral components
• New viruses assembled, leave host cell • Host cell damaged to killed in process • Viruses then attack more healthy cells www.indiandentalacademy.com
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Viruses • Tend to mutate – Difficult to acquire immunity, develop antibodies and vaccines
• Some alter host chromosomes – Leads to malignant cells and cancer
• Viruses difficult to control – Unique structure – Hide in host cells – Drugs cannot attack b/c lack own metabolic processes and structures www.indiandentalacademy.com
Chlamydiae, Rickettsiae, Mycoplasmas • Similar to bacteria and viruses • Divide by binary fission – Require living cells for reprod
• Chlamydiae – Very primitive; lack many metabolic processes – Common STD
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Chlamydiae Reproduction
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Rickettsiae • • • • •
Gram neg Live inside host cell Transmitted by insects (ticks, lice) Attack bv walls (rash, sm hemorrhages) Typhus fever, Rocky Mountain spotted fever
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Mycoplasma • Smallest cellular microbe • Lack walls – Not affected by antimicrobial drugs
• Common cause of pneumonia
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Fungi • Found everywhere • Infection results from 1-celled yeasts or multicellular molds • Eukaryotes • Growth promoted by warmth and moisture • Some beneficial – Produce yogurt, beer – Source of antibiotic drugs www.indiandentalacademy.com
Pathogenic Fungi • • • •
Tinea pedis Candida Histoplasma Ringworm
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Protozoa • Eukaryotes • Unicellular, mobile, lack cell wall, irreg shapes • Some can live indep (dead or organic matter); others are parasites
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Protozoa • Trichomonas vaginalis – Flagella, sexually transmitted, attach to mucous membrane and cause inflammation
• Plasmodium vivax – Malaria; nonmotile; found in RBC and undergo stages of life cycle
• Amoebas – Entamoeba histolytica • Parasite in lg intestines; cause amebic dysentery; resist phagocytosis • Infection spread thru oral-fecal route www.indiandentalacademy.com
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Other Parasites: Helminths • NOT microorganisms; but are parasitic worms • Multicellular, eukaryotic, vary in size • 3 stage life cycle – Ovum – Larva – Adult
• Found in intestines, blood • Diagnosis by observation of ova in stool specimen • Common in NA: – Pinworms, hookworms, whipworms, round worms www.indiandentalacademy.com
Ascaris (Round worm)
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Principles of Infection: Transmission • Chain of events • Reservoir: Source of infection – Person with obvious infection – Carrier – Animal – Contaminated food, water, soil, equipment
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CHAIN OF INFECTION
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Modes of Transmission • Direct contact • Indirect contact • Droplet transmission • Hands • Vector-borne • Nosocomial
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Host Resistance • What factors would decrease host resistance? • Prophylactic antimicrobial medication – Required for indiv w/ low resistance prior to exposure to microbes
• Interferon – Proteins produced by human host cells • In response to viral invasion of cell – “Save yourselves”!!! www.indiandentalacademy.com
Virulence and Pathogenicity • Pathogenicity: capacity of microbes to cause disease • Virulence: degree of pathogenicity of specific microbe – Based on: • • • •
Invasive qualities Toxic qualities Presence of pili or fimbrae for adhesion Ability to avoid host defenses (mutate) www.indiandentalacademy.com
Drug Resistant Microbes • Staphylococcus aureus • Neisseria gonorrhoeae • Myobacterium tuberculosis • Streptococcus pneumoniae • Haemophilus influenzae www.indiandentalacademy.com
Steps to Minimize Risk of Infection 1. Locate, remove reservoir host 2. Block portal exit of microbes from reservoir 3. Know mode(s) of transmission of specific infections 4. Block portals of entry 5. Cleaning 6. Sterilization 7. Disinfectants 8. Antiseptics www.indiandentalacademy.com
CHAIN OF INFECTION
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The interaction between the 6 elements of the chain determine whether an infection will result.
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Development of Infection: Onset and Course • Incubation period – Organism present; no clinical signs, symptoms
• Prodomal period – Symptoms; don’t feel like yourself
• Acute period – Fully developed infection
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Development of Infection: Clinical Signs and Symptoms • Local signs – Inflammation – Purulent exudate if bacterial infection; serous exudate if viral – Tissue necrosis – Lymphadenopathy – Respiratory effects
• Systemic signs – Fever, fatigue, headache, nausea www.indiandentalacademy.com
Development of Infection: Diagnostic Tests • Cultures and stains – bacteria
• Blood tests – Bacteria • Leukocytosis
– Virus • Leukopenia
– Increase in neutrophils w/ acute; increase in lymphocytes and monocytes w/ chronic
• Radiologic exams www.indiandentalacademy.com
Guidelines for Antimicrobial Drug Usage • • • • • •
Regular intervals Until prescribed meds used Follow directions Choose best drug Patient allergies Antibiotics = BACTERIA, NOT VIRUSES! www.indiandentalacademy.com
Classification of Antimicrobial Drugs • • • • •
Antibiotics Antimicrobials Bactericidal vs. Bacteriostatic Broad vs. Narrow Spectrum 1st and 2nd Generation Drugs
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Mode of Action • Antibacterial drugs • Antiviral drugs • Antifungal drugs
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Mode of Action: Antibacterial Drugs • Operate in 1 of 4 ways: • Interferes with bacterial wall synthesis – Ex: Penicillin
• Increase permeability of bacterial cell membrane – Ex: Polymyxin
• Interferes w/ protein synthesis and reproduction – Ex: Tetracyclin
• Interferes w/ synthesis of essential metabolites – Ex: Sulfonamides www.indiandentalacademy.com
Mode of Action: Antiviral Drugs • Decrease reproduction of virus inside host cell – Does not destroy virus
• Meant to control not cure • May interfere with: – – – –
Viral attachment to host cell Shedding of protein coat Protein synthesis Viral replication
• Significant adverse effects www.indiandentalacademy.com
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BIBLIOGRAPHY • Clinical Periodontology 9th Ed, by –Newman, Takei and Carranza • Oral microbiology 4th edition by Philip marsh and Michael v.martin. • Text book of microbiology for dental students by Pro C.P Baveja • essential microbiology for dentistry by L.P Samaranayake. • Jawetz,Melnick and adelberg’s medical microbiology by Brooks,butel and morse • lippincott’s illustrated reviews : microbiology by William,harriet and bruce. • Textbook of diagnostic microbiology by Coonie R.Mabon and george manuselis • Textbook of microbiology 6th edition by ananthanarayan and CKJ Paniker. www.indiandentalacademy.com
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