Controlling Microbial Growth (#1) Flashcards
types of microbial control methods (4):
1) physical agents
2) chemical agents
3) mechanical removal methods
4) biological agents
the destruction or removal of vegetative pathogens but not bacterial endospores; usually used only on inanimate objects
disinfection
the complete removal or destruction of all viable microorganisms; used on inanimate objects
sterilization
chemicals applied to body surfaces to destroy or inhibit vegetative pathogens
antisepsis
chemicals used internally to kill or inhibit growth of microorganisms within host tissues
chemotherapy
destruction or removal of ALL viable microorganisms (including endospores + viruses); have to be harsh enough to kill endospores; doesn’t have to be long-lasting but KILLS ALL
sterilization
sterilization uses _______
sterilants
removal of organic matter (things microbes like to eat); usually use some type of agent; ex: wipes
decontamination
killing, inhibition, or removal of pathogenic microorganisms; microbes in endospores will probably still be alive
disinfection
disinfection uses _______
disinfectants
disinfection is used ON ______ objects
inanimate
the goal of _______ is to reduce microbial load, but get rid of pathogens
disinfection
reduction of microbial population to levels deemed “safe” – based on public health standards**
sanitization
T/F: sanitation and sanitization are the same thing
false
removal of trash
sanitation
sanitization uses ________ which are held up to public health standards
sanitizers
prevention of infection of living tissue
antisepsis
chemical agents that kill or inhibit growth of microorganisms when applied to tissue
antiseptics
antiseptics are also called “______”
germicides
sometimes ______ will be labeled as antisepsis as its purpose
sanitizers
what does “antisepsis” mean?
getting rid of … rotting
use of chemicals to kill or inhibit growth of microorganism within host tissue
chemotherapy
example of chemotherapy =
antibiotics
T/F: antibiotics are made in nature by bacteria + fungi
true
physical methods to control microbes (4):
- heat (moist or dry)
- low temperature
- radiation
- filtration
type of heat that has BETTER penetration power than the other; has water in it; can’t use it all the time with certain bacteria
moist (compared to dry)
type of physical method: destroys bacteria, fungi, and viruses
moist heat
3 types of moist heat:
- boiling
- pasteurization
- autoclaving
type of moist heat method: will not always destroy endospores, so will NOT necessarily sterilize – good at disinfection tho
boiling
some endospores can withstand ____ hours of boiling
20 hours
type of moist heat method: way to heat up food that decreases microbial load and pathogens, but does NOT sterilize
pasteurization
type of moist heat method: only type that CAN sterilize; puts steam under pressure to raise temperature
autoclaving
controlled heating at temperatures well below boiling; used for wine, milk, and other beverages
pasteurization
pasteurization kills _______ and slows spoilage + reduces the total microbial load (not exactly for a long per.) but does NOT sterilize
pathogens
bringing foods and liquids to very HIGH temps, but only for a short period of time
ultra-pasteurization (not rlly pasteurization)
in autoclaving, the _____ is doing all of the killing; effective against ALL types of microbes = sterilization
temperature
autoclave pressure =
15 psi
autoclave temperature (of steam) =
121°C
autoclave time =
15 - 20 min. (at least 10 min)
_____ objects take longer to autoclave (need it to penetrate all the way through)
larger
you can’t autoclave ______ (will melt), a lot of _______, or things that CANNOT be exposed to ______
plastic, metals; water
autoclaving puts steam under ______ to increase the temperature
pressure
T/F: it takes a while for pressure to build up to get to 121°C in autoclaving
true
it takes at least ____ ______ for one autoclave cycle
1 hour
boiling time + temp required to kill bacteria endospores:
2-over 800 minutes @ 100°C
autoclaving time + temp required to kill bacteria endospores:
0.5-12 minutes @ 121°C
type of physical method: less effective than moist heat sterilization
dry heat sterilization
2 ways to dry heat sterilize:
- dry heat sterilizer (oven)
- flaming (incineration)
T/F: dry heat requires higher temperatures and longer exposure times since penetrative power is weaker
true
for dry heat sterilization using an oven, items must be subjected to what temperature and for how long to sterilize?
160-170°C for 2-3 hours
for
flaming is also called
incineration
method of dry heat sterilization: method of STERILIZATION but SHORT-lived
flaming (incineration)
2 types of LOW TEMP method (physical method):
- freezing
- refrigeration
type of LOW temp method: stops microbial reproduction due to lack of liquid water; SOME microorganisms killed by ice crystal disruption of cell membranes
freezing
freezing temp =
-20°C (or 0°F)
T/F: the number of microbes when put into a freezer is roughly the same number when you take it out from freezing
true!
type of LOW temp method: SLOWS microbial growth and reproduction; not stopping – why things still spoil
refrigeration
what kind of bacteria still grow when refrigerated?
pyschrophiles
refrigeration temp =
4°C (or 41°F)
freezing _____ microbial reprod. and refrigeration ______ microbial reprod.
stops; slows
2 types of radiation
- UV (ultraviolet) radiation
- ionizing radiation
type of radiation: causes thymine dimers in DNA; POOR penetrating power; non-ionizing radiation; limited to the disinfection of SURFACES, air, and water; does not penetrate glass, plastic, dirt films, etc.
UV radiaiton
most bactericidal (killing bacteria) wavelength in UV radiation =
260 nm
most bactericidal wavelength in general =
greater than or equal to 400 nm; can’t see
- aka UV radiation does not kill most bacteria
UV radiation causes ______ _____ in DNA
thymine dimers
UV radiation is limited to what kind of things (3)?
- surfaces
- air
- water
UV radiation can ______ surfaces but would have to expose every area of surface to be considered this
sterilize
what type of UV light is the 260 nm UV radiation?
UV-C
what does the formation of thymine dimers in DNA from UV radiation cause?
replication errors + even DNA to break (can kill an organism)
type of radiation: beta, gamma, and x-rays; penetrates DEEP into objects; pushes electrons out of orbit
ionizing radiation
ionizing radiation can be used for _______ sterilization
cold
what do you use cold sterilization (ionizing radiation) for (3)?
- antibiotics
- medical supplies
- food
type of cold sterilization product: manufacturers of this use this method to sterilize it; would denature in heat
antibiotics
why is cold sterilization good for food?
sterilizes it but doesnt cook it (ex: ground beef)
what 3 types of waves are involved in ionizing radiation?
- beta
- gamma
- x-rays
type of physical method: reduces microbial populations; sterilization of heat – sensitive solutions; also used for air
filtration
since filtration uses the sterilization of heat with SENSITIVE solutions, you must use a membrane filter with a defined _____ ______
pore size
filtration is good at ______ and potentially _____ depending on size of pore in filter
disinfecting; sterilizing
type of pore filters (3):
- depth pore filters
- membrane filter
- nucleopore filters
type of pore filter: no defined size of pore
depth pore filter
type of pore filter: pore size is undefined but smaller than depth pore filters
membrane filter
type of pore filter: PRE-defined pore filters; best at sterilizing
nucleopore filters
CHEMICAL control of microbial growth involves the use of what?
antimicrobial agents
a natural or synthetic chemical that kills or inhibits the growth of microbes
antimicrobial agent
antimicrobial agents can be -______ or -______
- cidal
- static
suffix indicating a chemical agent KILL; kills pathogens and many non-pathogens, but not necessarily endospores
-cidal
suffix indicating a chemical agent that INHIBITS growth
- static
-cidal =
to kill
-static =
stop
types of antimicrobial agents (2):
antibiotics + semi-synthetics
bactericidal, fungicidal, and viricidal means that the agent does what?
kills them
bacteriostatic, fungistatic, and viristatic means that the agent does what?
inhibits growth
bacterial growth graphs (log cell number growth vs. time) invovle what 2 types of counts?
- total cell count
- viable cell count
bacterial growth graph: total cell count + viable cell count encounter a stationary period when the agent is present
bacteriostatic
bacterial growth graph: viable cell count decreases significantly when agent is applied, but total cell count stays the same (levels off)
bactericidal
bacterial growth graph: BOTH the total cell count + viable cell count decreases when the agent is applied
bacteriolytic
the effectiveness of antimicrobial drugs can be determined based off of what 2 concentrations?
- MIC (minimal inhibitory concentration)
- MLC (minimal lethal concentration)
type of antimicrobial effect. concentration: lowest concentration that INHIBITS growth of pathogens; doesnt mean it kills it
MIC (minimal inhibitory concentration)
type of antimicrobial effect. concentration: lowest concentration of drugs that KILLS pathogens
MLC (minimal lethal concentration)
MLCs are how much stronger than MICs to have a killing effect?
2-4x stronger [ ]
which of these describes sterilization?
a) wiping food crumbs off your kitchen table
b) running dirty dishes through the dishwasher
c) spraying a bleach solution on your bathroom counter
d) boiling water before you drink it
e) none of the above
e) none of the above
to determine the level of antimicrobial activity, you can perform what type of test?
dilution susceptibility test
a dilution susceptibility test can only detect which type of concentration?
MIC
dilution susceptibility test: smallest amount of agent needed to inhibit the growth of a test organism is the ______
MIC
in the dilution susceptibility test, which tube determines the MIC
tube with no turbitity (no growth)
dilution susceptibility test: broth from which microbe can’t be recovered is the _____
MLC
in the dilution susceptibility test, you would have to _____ to determine the MLC
plate
in the dilution susceptibility test, the tubes increase in dilution by a factor of ___ - _____
2-4
disk diffusion test steps (4):
- inoculate plate with a liquid culture of a test organism
- disks containing antimicrobial agents are placed on surface
- incubate for 24-48 hrs
- test organism shows susceptibility to some agents, indicated by inhibition of bacterial growth around disks (zones of inhibition)
in the Kirby-Bauer Method, you measure the ____ zone of inhibition
WHOLE
T/F: sometimes it is hard to isolate bacterium from patients to perform a disk diffusion test to determine the effectiveness of an antimicrobial drug
true
big zones of inhibition =
better (bacteria is more SENSITIVE to agent)
antimicrobial agents in disk diffusion tests get ______ concentrated as it diffuses out
less
factors influencing the effectiveness of an antimicrobial agent (6):
- population size
- population composition
- concentration / intensity of the agent
- duration of exposure
- temperature
- local environment
factor influencing the effectiveness of an antimicrobial agent: looks at species, endospores, persister cells, biofilms, age of cells
population composition
T/F: you don’t have to perform studies to make sure drug gets to desired part of body + reaches the MIC where it needs to be (aka concentrated enough)
false (you do…)
______ cells are harder to kill
older (aka persister cells)
you can use less antimicrobial agents when it is more ______
concentrated
factor influencing the effectiveness of an antimicrobial agent: looks at presence of organic matter, pH, visocity
local environment
used to determine the effectiveness of certain antimicrobials
Kirby-Bauer Method
the Kirby-Bauer Method table relates ZONE DIAMETER to degree of microbial ______
resistance
if the zone of inhibition is small, that means the bacteria is ______ to the agent
resistant
if the zone of inhibition is big, that means the bacteria is _______ to the agent
sensitive
