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 publicex: 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 treatedEx: can’t use harsh chemicals

on humans

2. Relative SusceptibilityWhat is the toughest to kill at

that site and aim for it

3. Environmental ConditionsTemp & 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 pressurepressure chamber used for food packing

How do you know when something has been sterilized (2 ways)?1. Chemical tab that changes color2. 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 MethodsPhenols- derived from phenol molecules that have chemically modified- denature proteins & disrupt cell membranes- work in health care settings & laboratories, remain active on surfacesEx: clove oil, pine oilBisphenolics- Lysol, garbage bags, diapers

Alcohols- bactericidal, fungicidal, virucidal, not effective against fungal spores or bacterial endosporesEx: rubbing alcohol, drinking alcohol (pure alcohol is not effective because denaturation requires water)

HalogensEx: iodine, chlorine, bromine, fluorineIodophor- releases iodine slowly (betadine)

Oxidizing AgentsEx: peroxides, ozone, peracetic acidHydrogen peroxide- not for open wounds, broken down by body (bubbling)

SurfactantsGood degerming agents, but poor antimicrobial agentsEx: soaps & detergents

Heavy MetalsEx: arsenic, zinc, mercury, silver, copperSilver nitrate, silver cholideSilver killing Strep and Staph

AldehydesContain terminal –CHO groupsEx: glutaraldehyde, formaldehydeFormalin- embalming, surgical instruments

Gaseous AgentsEx: ethylene oxide, propylene oxide, beta- propiolactonePenetrate paper & plastic wraps, plastic lab equipment, mattresses, pillows, dried food

EnzymesLysozyme- human tears can destroy microbesRemoves prions on medical instruments

AntimicrobialsEx: treatments of disease: antibiotics, semisynthetics, synthetics (modified antibiotics)

See Table 9.5 in Textbook for Summary!!!