The Control of Microbial Growth 4

sepsis

bacterial contamination

asepsis

absence of significant contamination

aseptic surgery technique

prevent the microbial contamination of wounds

sterilization

removing and destroying all microbial life (not including viruses)

commercial sterilization

killing C. botulinum endospores from canned goods

disinfection

destroying harmful microorganisms

antisepsis

destroying harmful microorganisms from living tissue

degerming

the mechanical removal of microbes from a limited area

sanitization

lowering microbial counts on eating utensils to safe levels

biocide (germicide)

treatments that kill microbes

bacteriostasis

inhibiting growth , not killing, microbes

chemotherapy

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

-cidal or -static

antimicrobial agents can be

-cidal

means to kill; pathogens and many nonpathogens but not necessarily endospores

-static

inhibits growth

rate of microbial death

microorganisms are not killed instantly; die at a constant rate

are not

microorganisms are or are not killed instantly

constant

microorganisms die at a ______ rate

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

conditions influencing the effectiveness of antimicrobial agent activity

population size

larger populations x smaller populations

position composition

microorganisms x sensitivity to antimicrobial agents

concentration or intensity of an antimicrobial agent

higher concentrations x lower concentrations

duration of exposure

longer exposure --> more organisms killed

higher

_____ temperatures usually increase amount of killing

local environment

many factors (pH, viscosity, and concentration of organic matter) can profoundly impact effectiveness

biofilms

organisms in ____ are physically altered and less susceptible to many antimicrobial agents

alteration of membrane permeability, damage to proteins (enzymes), damage to nucleic acids

actions of microbial control agents

alteration of membrane permeability

damage to the lipids or proteins of the plasma membrane causes cellular content to leak into the surrounding medium

damage to proteins (enzymes)

denaturation of proteins due to heat or chemicals

damage to nucleic acids

by heat, radiation, or chemicals

heat, filtration, low temperatures, high pressure, desiccation, osmotic pressure, radiation

physical control methods

denatures

heat ____ enzymes

varies

heat resistance ___ among different microbes

thermal death point (TDP)

lowest temperature at which all cells in a liquid culture are killed in 10 minutes

thermal death time (TDT)

minimal time for all bacteria in a liquid culture to be killed at a particular temperature

TDP and TDT

used as guidelines to determine treatment to kill bacterial population

decimal reduction time (DRT)

minutes to kill 90% of a population at a given temperature

moist heat sterilization

denatures proteins, degrades nucleic acids, and disrupts membranes

moist heat sterilization

boiling, free-flowing steam, autoclave

free-flowing steam

destroys viruses, fungi and bacteria but will not destroy all viruses or endospores and does not sterilize

autoclave

steam under pressure

121 C

autoclave temperature at 15 psi for 15 minutes

all

autoclave kills ____ organisms and endospores

contact the item's surface

steam in the autoclave must

true

T/ F: autoclave sterilizes

false

T/ F: free-flowing steam sterilizes

longer

large containers require ____ sterilization times

test strips

used to indicate sterility

pasteurization

reduces spoilage organisms and pathogens

72 C for 15 sec

high-temperature short-time (HTST)

140 C for 4 sec

ultra-high-temperature (UHT)

63 C

temperature of pasteurization for 30 minutes

pasteurization

used for milk, beer, and other beverages

thermoduric

what organisms survive pasteurization?

less, higher, longer

dry heat sterilization is ____ effective than moist heat sterilization, requiring ____ temperatures and ____ exposure times

dry heat sterilization

oxidizes cell constituents and denatures proteins

dry heat sterilization

flaming, incineration, hot-air sterilization

bench top incinerators

used to sterilize inoculating loops used in microbiology laboratories

filtration

passage of substance through a screen like material

filtration

used for heat-sensitive materials