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


1.
2.
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 Sterilizationflash 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, xrays, 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, betapropiolactone
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!!!