Ch 9 Controlling Microbes

Sterilization- removal/destruction of all microbes (except prions) Aseptic- environment free of contamination of pathogens Disinfection- physical or chemical agents to destroy pathogens ex: bleach, alcohol, UV light, heat Antiseptic- chemical used on skin or tissue

Degerming- removal of microbes from a surface by scrubbing ex: washing hands Sanitization- disinfecting places and utensils used by the public ex: steam, high pressure water Pasteurization- heat to kill, reduce spoilage Stasis/static- inhibits microbial metabolism & growth but doesn’t kill Cide/cidal- destroy permanently

Microbial Death- permenant loss of reproductive ability 2 categories of action of Antimicrobial Agents: 1. Alteration of Cell Walls & Membranes Allows cellular contents to leak & water to come in (bursting) Lysin lysing bacteria 2. Damage to Proteins & Nucleic Acids Disrupts metabolic reactions & structure

Factors Affecting the Efficacy of Antimicrobials 1. Site to be treated Ex: can’t use harsh chemicals on humans 2. Relative Susceptibility What is the toughest to kill at that site and aim for it 3. Environmental Conditions Temp & pH affect methods

Methods for Evaluating Disinfectants & Antiseptics 1. Phenol Coefficient Compares a given agent’s ability to control microbes to that of phenol under standardized conditions If greater than 1= more effective than phenol 2. Use-dilution test Cylinders dipped into substance to check microbial growth 3. Kelsey-Sykes Capacity test Place bacteria in specific concentration of disinfectant 4. In-use test Swabs from actual objects before & after disinfectant More realisitic *Note: first 3 are under controlled conditions

Physical Methods for Control 1. Heat is used for sterilization, canned goods Thermal Death Point- lowest temp that kills all cells in a broth in 10mins Thermal Death Time-time it takes to completely sterilize a volume of liquid at a set temp Decimal Reduction Time-time required to destroy 90% of microbes in a sample Clostridium botulinum causes botulism toxin inside sealed cans

2. Moist Heat- denatures proteins & destroys cytoplasmic membranes 1) Boiling-water boils at lower temps at higher elevations because of atmospheric pressure is lower, so you have to boil longer Does boiling actually sterilize? No, sanitizes not sterilize, endospores can survive 2) Autoclaving- add pressure pressure chamber used for food packing How do you know when something has been sterilized (2 ways)? Chemical tab that changes color Melt plastic beads

3)Pasteurization- heating enough to destroy the microorganisms that cause spoilage without raising the temps to ruin taste Flash Pasteurization –high temp, short time (milk) 4) Ultrahigh-Temperature Sterilization- flash heating to rid of ALL microbes, extremely hot for 1 second (dairy creamer)

3. Dry Heat- high temps for longer period of time

Others: 1)Refrigeration- halts growth on food 2) Dessiccation- drying (fruits, beans, nuts) Lyophilization-freeze drying, liquid Nitrogen 3) Filtration-passage of a fluid through a sieve to trap particles ex: antibiotics, vaccines, enzymes 4) Osmotic Pressure- high concentrations of salt/sugar in foods ex: jams, jellies, honey, jerky

5) Radiation- high speed subatomic particles through cells 6) Ionizing Radiation-gamma, x-rays, penetrate further and used for meats, spices, fresh fruits and vegetables, kills insect larvae 7) Nonionizing Radiation-UV light, used in hospitals and disinfecting air and transparent fluids

Chemical Methods Phenols- derived from phenol molecules that have chemically modified - denature proteins & disrupt cell membranes - work in health care settings & laboratories, remain active on surfaces Ex: clove oil, pine oil Bisphenolics- Lysol, garbage bags, diapers Alcohols- bactericidal, fungicidal, virucidal, not effective against fungal spores or bacterial endospores Ex: rubbing alcohol, drinking alcohol (pure alcohol is not effective because denaturation requires water) Halogens Ex: iodine, chlorine, bromine, fluorine Iodophor- releases iodine slowly (betadine)

Oxidizing Agents Ex: peroxides, ozone, peracetic acid Hydrogen peroxide- not for open wounds, broken down by body (bubbling) Surfactants Good degerming agents, but poor antimicrobial agents Ex: soaps & detergents Heavy Metals Ex: arsenic, zinc, mercury, silver, copper Silver nitrate, silver cholide Silver killing Strep and Staph Aldehydes Contain terminal –CHO groups Ex: glutaraldehyde, formaldehyde Formalin- embalming, surgical instruments

Gaseous Agents Ex: ethylene oxide, propylene oxide, beta- propiolactone Penetrate paper & plastic wraps, plastic lab equipment, mattresses, pillows, dried food Enzymes Lysozyme- human tears can destroy microbes Removes prions on medical instruments Antimicrobials Ex: treatments of disease: antibiotics, semisynthetics, synthetics (modified antibiotics) See Table 9.5 in Textbook for Summary!!!