1. Ch 9 Controlling Microbes

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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)

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

11. 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

12. 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

13. 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)

14. 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

15. 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!!!