control of microbial growth Flashcards
define sterilization
destruction or removal of all viable organisms, including spores or acellular entities, from an object or habitat
what does sterilization remove
EVERYTHING (organisms and spores)
T or F: sterilization removes spores
true
define disinfection
killing/inhibiting/removing pathogenic organisms
does disinfection kill everything?
no; it kills/removes PATHOGENS
what is used to disinfect
disinfectants
define sanitization
reduction of microbial populations to LEVELS DEEMED SAFE (based on public health standards)
define antisepsis
destruction/inhibition of microbes on LIVING TISSUE, thereby preventing infection
goal of sanitization?
reduce microbes to safe levels for the public
goal of antisepsis?
prevent infection on living tissue by destroying microbes
what are antiseptics
chemical agents that kill/inhibit growth of microbes when applied to tissue
list 2 antiseptics
iodine or alcohol
what does “cide” mean in cidal agent
the agent kills
what does “static” mean in static agent
the agent inhibits growth
which kills: cidal or static agents
cidal
which inhibits: cidal or static agents
static
are enveloped viruses and bacteria susceptible or resistant to antimicrobial agents
susceptible
are mycobacteria, endospores, and prions susceptible or resistant to antimicrobial agents
resistant
how does population size influence the efficacy of antimicrobial methods
larger populations take longer to kill than small populations
do small or large populations of bacteria take longer to kill
large
how does population composition influence the efficacy of antimicrobial methods
microbes differ markedly in their sensitivity to antimicrobial agents
how does concentration/intensity of antimicrobial agents influence the efficacy of antimicrobial methods
higher concentrations/intensities kill more rapidly
how does duration of exposure to the agent influence the efficacy of antimicrobial methods
longer exposure to the agent = more organisms killed
how does temperature influence the efficacy of antimicrobial methods
higher temperatures usually increase the amount of killing
how does the local environment in which a microbe is in influence the efficacy of antimicrobial methods
many factors can profoundly impact effectiveness, ie pH, viscosity, and concentration of organic matter
what is the mode of action for heat as an antimicrobial
denatures proteins, disrupts integrity of PM/cell wall, and is disrupts the structure/function of nucleic acids
what are the two types of heat used as an antimicrobial
moist heat and dry heat
what are the three types of moist heat
boiling, autoclaving, and pasteurization
does boiling sterilize
no
if boiling doesn’t sterilize, what does it do
disinfects
what does boiling kill
most bacteria, but not spores
what doesn’t boiling kill
spores
how does autoclaving work
makes use of saturated steam under pressure to bring the temp above 100 C
what autoclaving conditions do we use
121 C and 15 psi
what does autoclaving kill
all vegetative bacteria and spores
does autoclaving sterilize
yes
in the autoclave, how is time affected when we have lots of volume
time increases as volume increases
T or F: we pack the autoclave as tight as we can to sterilize lots of stuff
false; the steam needs to be able to contact all surfaces, so don’t pack tightly
T or F: we want to wrap things in tinfoil when in the autoclave
false; tinfoil is impermeable to steam, so anything wrapped will not be sterilized
T or F: we want to loosen the lids of anything in the autoclave
true; this is because of the high pressure conditions
what two types of indicators can be used in the autoclave
chemical or biological
describe a chemical indicator in the autoclave
autoclave tape: lines will turn black once high heat is reached
what is the downside of autoclave tape
only shows that the heat was reached, doesn’t actually confirm sterility
describe how a biological indicator of the autoclave works
use a sterility indicator: a small vial has a tube that contains endospores and this is put into the autoclave. After, the vial is incubated, and if spores are present they will germinate, and we will see a color change occur
does pasteurization sterilize
no (for the most part)
if pasteurization doesn’t sterilize, what does it do
it eliminates any pathogenic bacteria and reduces the total number of nonpathogenic bacteria
list the 3 different pasteurization processes
low-temp holding, high-temp short-time, and ultra-high temp
what are the settings for low-temp holding (pasteurization)
68.2C for 30 min
what is low-temp holding used for
beer, fruit juice, smaller volumes of milk
what are the conditions for high-temp short-time (pasteurization)
72C for 15 sec
what is high-temp short-time used for
industry milk and other dairy products
what are the conditions for ultra-high temp (pasteurization)
138C for 3 sec
what is ultra-high temp used for
milk that doesn’t require refrigeration until opened
which type of pasteurization sterilizes
ultra-high temp
what are the two forms of dry heat used as an antimicrobial
incineration and the oven
what is incineration
used in the place of an alcohol lamp/bunsen burner
does incineration sterilize
yes
what is the oven/ how do you use it
you put something in, turn the temp to 171C for 1 hour or 160C for 2 hours
does the oven sterilize
yes
what types of materials do we use dry heat for
powders, materials that can become damaged by steam
what materials CANT we use dry heat for
certain materials (ie rubber and plastics)
what are two methods of low temps as antimicrobial
refrigeration and freezing
what temp range is refrigeration
0-7 C
what temp range is freezing
below 0 C
do low temps sterilize?
no
if low temps don’t sterilize, what do they do
they decrease microbial metabolism and growth
are low temps cidal or static
static
low temps are ___static
bacteriostatic
how does desiccation work
removes liquid water which inhibits microbial growth
what is lyophilization
culture is frozen in liquid nitrogen and then subjected to a vacuum to remove frozen water
what is the final product of lyophilization
a powdered pellet
what is filtration as an antimicrobial method
fluid or air passes through a sieve that will trap the desired particles
does filtration sterilzie
yes!
what size pores are in the filter paper of filtration + what is the purpose of this size
0.22 um will trap large viruses and most bacteria. 0.2 um is often used
describe two ways how we can filter air
using an N95 mask excludes 95% of particles that are greater than 0.3 um in size (most microbes), or you can use a HEPA filter
describe how osmotic pressure is used as an antimicrobial agent
high concentrations of sugar or slat inhibit microbial growth (hypertonic environment) bc this dries out the cells
list two types of radiation that control microbial growth
ionizing and non ionizing
what is an example of ionizing radiation
gamma rays
how does ionizing radiation work
penetrates deep into objects
does ionizing radiation sterilize
yes
what is ionizing radiation used for
sterilization of antibiotics, surgical sutures, plastic disposable lab supplies, and food
give an example of non ionizing radition
UV light
wavelength of UV light?
260 nm
does nonionizing radition sterilize
yes
how does non ionizing radiation work
is limited to surface sterilization since it doesn’t penetrate well
what is non ionizing radiation used for
air, transparent fluids, surfaces of objects
