Antiseptics

High pressure is called pascalization. It is used to kill many pathogens by exposing food to high pressures. It will not always kill the endospores. Hyperbaric oxygen is used in a medical setting to fight the growth of anaerobic organisms using both oxygen and high pressure.

Drying or desiccation will preserve many types of foods but the organisms will often grow back if the environmental conditions involve higher temperatures and higher water content. Lyophilization is used in the laboratory, which involves freeze-drying the organism. These can later be stored in dry conditions, even at room temperature. Some foods are dried with salt or sugar to decrease the ability of organisms to grow.

Ionizing radiation can kill organisms. It can pass through cells and damage cellular components. There will be mutations to the food products that have been irradiated. Many processed foods in plastic and paper can be treated with ionizing radiation and certain laboratory equipment can be sterilized this way. UV light or nonionizing radiation can kill organisms. UV light-related purifiers will clean water for campers. It does not penetrate solid objects, however, so it has limited capabilities.

Other techniques for reducing the organisms in a substance includes sonication, which involves high-frequency ultrasound waves. HEPA filters are used to sterilize the air in certain clinical settings. They are also found in airplanes, automobiles, air purifiers, and air conditioning systems. Membrane filters are used to filter antibiotic and vitamin solutions as well as culture media in order to sterilize the liquid without the damaging effects of heat.

ANTISEPTICS

Antiseptics involve chemical control of microorganisms. The earliest antiseptic used was phenol. This is what Listerine is made from. It is too irritating to be used on skin surfaces in surgery. There are related compounds called phenolics. These include products called Lysol and Phisohex. Triclosan is used in antibacterial hand soaps and toothpaste. Triclosan is bactericidal.

Other antiseptics contain heavy metals but these are also damaging to humans by denaturing proteins. These include mercury, which was used once to treat syphilis.

Tincture of mercury was once used as an antiseptic. Silver is an antiseptic, such as is seen in Silvadene cream. Silver nitrate was once used as an eyedrop in newborns. Others include copper sulfate, nickel-containing products, and zinc. Zinc oxide is used in diaper creams to fight infection.

The halogens, such as iodine, fluorine, and chlorine are antimicrobial. Povidone-iodine is used to scrub before surgery and in surgical surfaces. Water is chlorinated in order to remove bacteria, such as is seen in swimming pools. Chloramine tablets are used to disinfect water after a natural disaster or in the military. These substances will not kill all microorganisms. Fluoride is used in toothpastes and in certain water supplies in order to prevent tooth decay.

Alcohols will kill bacteria, fungi, and some viruses. They do not kill spores but will inhibit the germination of spores. They can be irritating to skin. Both ethanol and isopropyl alcohol will kill bacteria and will be good anti-infectives.

Surfactants involve most soaps or detergents. They are not antiseptics but are degerming agents by removing bacteria specifically from a surface. Some soaps, however, will contain an antiseptic or bacteriostatic agent.

Bisbiguanides are newer agents that include things like chlorhexidine. These will kill most organisms except for Pseudomonas aeruginosa. It will also kill enveloped bacteria but is ineffective in killing the organism causing tuberculosis, spores, or nonenveloped viruses. It is currently commonly used for surgical scrubbing and to treat gingivitis.

Alkylating agents will inactivate certain enzymes as well as nucleic acids. This is what’s seen in formaldehyde. It will decrease the temperature necessary to sterilize a substance. It is used to store tissues and organs after autopsies and is used in embalming. Glutaraldehyde is similar to formaldehyde and is used to disinfect surgical or other medical equipment but is too irritating to the skin to be used as an antiseptic. Ethylene oxide is a form of gaseous sterilization. All alkylating agents are carcinogenic so they must be used carefully.

Peroxygens are things like hydrogen peroxide. They can be used as disinfectants but can be irritating to the skin, delaying skin healing and causing scarring of tissue. It is what’s frequently used in contact lens cleaners. Bacteria that contain peroxidase or catalase

will have resistance to hydrogen peroxide because they will be protective against hydrogen peroxide. Gaseous hydrogen peroxide will be used sometimes to sterilize equipment or entire rooms.

High-pressure carbon dioxide is a supercritical fluid that can be used in a chamber to penetrate cells and kill endospores. It works better if cycled between pressurization and depressurization or if heat is applied as well. It can treat foods and be used in certain medical equipment sterilization because it doesn’t destroy things or break down things.

There are natural and artificial food preservatives, such as nitrites, nitrates, and propionic acid. These will not change the taste or properties of food. Others are benzoic acid or sodium benzoate, used in sweet food preservation by inhibiting the citric acid cycle.

Natural food preservatives, such as nisin, which is made by Lactococcus lactis, can be used. It is used to preserve certain beverages, meats, and certain cheeses. Natamycin is a natural antifungal product used in cottage cheese and other types of cheese.