Chapter 4.17 - 4.19: Controlling Microbial Growth

sterilization

destruction or removal of ALL viable microorganisms (including endospores and viruses)

decontamination

physical process- removing big things

disinfection

killing, inhibition, or removal of pathogenic microorganisms (used on inanimate objects)

sanitization

reduction of microbial population to levels deemed safe (based on public health standards)

antisepsis

prevention of infection of living tissue

germicides (antiseptics)

chemical agents that kill or inhibit growth of microorganisms when applied to tissue (animate objects)

example of antiseptics

alcohol before a vaccine

chemotherapy

use of chemicals to kill or inhibit growth of microorganisms within host tissue

4 physical methods to control microbes

heat (moist + dry), low temperature, radiation, filtration

moist heat

destroys bacteria, fungi, and viruses

3 types of moist heat control

boiling, pasteurization, autoclaving

is boiling sterilization

no

is pasteurization sterilization

no

is autoclaving sterilization

yes

pasteurization

controlled heating at temperatures well below boiling; kills pathogens present and slows spoilage

autoclave

effective against all types of microbes; can kill endospores (not prions)

pressure of autoclave

15 psi

temperature of autoclave

121 Celsius (steam)

time of autoclave

15-20 minutes

dry heat sterilization effectiveness

less effective than moist heat sterilization

dry heat sterilization requirements

requires higher temperatures and longer exposure times

example of dry heat sterilization

flaming (incineration)

2 kinds of low temperature control

freezing and refridgeration

freezing low temperature control

stops microbial reproduction due to lack of liquid water; some microorganisms are killed by ice crystals

refridgeration low temperature control

slows microbial growth and reproduction

ultraviolet radiation

non-ionizing radiation, poor penetrating power

what does UV radiation cause

thymine dimers in DNA

what is the limitation of UV’s poor penetrating power

limited to the disinfection of surfaces, air, and water

what can UV radiation not penetrate

glass, plastic, dirt films

ionizing radiation examples

beta, gamma, x-ray

ionizing radiation penetrating power

penetrates deep into objects for full sterilization

cold sterilization (ionizing radiation)

antibiotics, medical supplies, food

filtration

reduces microbial populations, sterilization of heat sensitive solutions

antimicrobial agent

a natural or synthetic chemical that kills or inhibits the growth of microbes

-cidal

indicates a chemical agent thats kills (pathogens or non pathogens, but not necessarily endospores)

-static

indicates a chemical agent that inhibits growth

minimal inhibitory concentration (MIC)

lowest concentration of drug that inhibits growth of pathogen

minimal lethal concentration (MLC)

lowest concentration of drug that kills pathogen

determining the level of antimicrobial activity using

dilution susceptibility test

zones of inhibition

a clear circular area where bacteria cannot grow due to antimicrobial agent

kirby-bauer method

used to determine the effectiveness of certain antimicrobials

(kirby bauer) diameter relates to

degree of microbial resistance

factors influencing the effectiveness of an antimicrobial agent

population size, population composition, concentration or intensity of the agent, duration of exposure, temperature, local environment