Chapter 7 The Control of Microbial Growth Flashcards
What does sepsis refer to?
refers to bacterial contamination
what does asepsis refer to?
the absence of significant contamination
what does it mean when there is a sterilization technique being used?
removes and destroys ALL microbial life
what does it mean when there is a commercial sterilization technique being used?
specifically aimed at killing Clostridium Botulinum endospores in canned goods which can cause botulism
what does it mean when there is a disinfection technique being used?
destroys HARMFUL microbes
what does it mean when there is an antiseptic technique being used?
destroys HARMFUL microbes from LIVING TISSUE
what does it mean when there is a degerming technique being used?
mechanical removal of microbes from a limited area
(such as using an alcohol wipe on skin before injecting a needle)
what does it mean when there is a sanitization technique being used?
lowers microbial counts to safe levels on eating utensils
what makes sterilization different from the rest of the cleaning techniques?
sterilization removes and kills ALL microbes
what is the distinction of antisepsis technique?
destroys harmful microbes from LIVING tissue
In what way do we chart the microbial death curve? what does this result in?
logarithmically; results in a straight line
why would the microbial death curve be a straight line?
because bacteria usually die at a constant rate
what are the four factors that affect the control of the microbial death rate?
time of exposure
type of microbe
number of microbes
environmental factors (temp/pH/O2/organic material)
on the scale that shows the relative susceptibility of different microbes which microbes are most resistant?
prions
on the scale that shows the relative susceptibility of different microbes which microbes are least resistant?
viruses with lipid envelopes
are gram positive or gram negative bacteria most/least resistant?
gram positive - less resistant
gram negative - more resistant
what is another name for a biocide?
germicide
what is a germicide?
treatment that kill microbes (like a specific type of microbe)
bonus question what is the bacteria that causes botulism?
Clostridium botulinum (endospores)
what kind of microbial control technique involves the application of an alcohol swab before injection
degerming
what is a fungicide an example of? what is it used for?
ex of biocide (germicide)
used to kill fungi
does the presence of organic material affect most antimicrobial treatments?
The presence of organic matter often INHIBITS the action of chemical antimicrobials
How does heat affect microbes?
kill microbes by denaturing their enzymes
what are the two types of heat that can kill microbes?
dry heat
moist heat
what causes the death of microbes in dry heat technique?
kills by oxidation effects
what microbial control is the use of dry heat and moist heat?
sterilization technique
what two ways can you perform dry heat?
direct flaming
hot air sterilization
which of the two DRY heat techniques takes longer? how does it work?
hot air sterilization
items are placed into oven at 170 for 2 hours
what are two examples of moist heat?
free-flowing system (autoclave)
boiling (pasteurization)
what causes the death of microbes in moist heat technique?
coagulates/denatures microbial enzymes
which of the two types of heat takes the longest to kill microbes?
dry heat
which type of heat is most effective at killing microbes? why?
Autoclave
high specific heat of water causes the moist heat to be transferred into cells (good at killing endospores this way)
what are the standard conditions for autoclave to ensure sterilization?
121 Celsius at
15 psi for
15 minutes
how does filtration act to sterilize solutions?
Mechanically separates microbes from substances by filtering through a screen-like material
different screen materials can trap different sized microbes
what two things are not effectively removed by filtration?
flexible bacteria (spirochetes)
wall-less mycoplasma
what are two types of filters that can be used?
HEPA filters (bigger particles)
membrane filters (smaller)
how does refrigeration work? does it kill microbes?
slows enzymes/ does not kill
(bacteriostasis)
how does fast freezing (deep freezing) work? does it kill microbes?
mostly slows enzymes/ does not kill
(bacteriostasis)
how does slow freezing work? does it kill microbes?
kills microbes
any water within bacteria will become crystals which disrupt cellular and molecular structure
Radiation causes damage to which cellular macromolecule?
DNA (nucleic acids)
what are two examples of ionizing radiation used to kill microbes?
X-rays
gamma rays
electron beams (used in post office)
how does ionizing radiation cause microbial death?
creates hydroxyl radicals which causes lethal mutations in DNA
how does nonionizing radiation cause microbial death?
damages DNA by creating thymine dimers which inhibit DNA replication
what is an example of nonionizing radiation?
ultraviolet
is microwaving an effective control of microbial growth?
no, it’s not really great at killing microbes
what is plasmolysis?
occurs from bacteria being put into a hypertonic solution causing water to leave out of the cell and ruptures the cell wall
what is the mode of action of alcohols?
usually denatures proteins
what microbes does alcohol work best on? not best on?
bacteria and fungi
not endospores and nonenveloped viruses
what are some examples of alcohols that can be used to kill microbes?
ethanol
isopropanol
Purell
GermX
what type of microbial control do alcohols offer?
degerming (best used on surfaces)
mode of action for phenols?
injures lipids of plasma membranes causing leaky cells
what is the chemical used in Lysol to give it its disinfecting properties?
cresols (phenols)
mode of action of biguanides?
disrupt plasma membranes (esp. gram-positive bacteria)
mode of action of halogens?
impairs protein synthesis and alters cell membranes
what is the example of biguanide?
in surgical hand scrubs
(mouthwash?)
what are examples of some halogens?
iodine
betadine
chlorine
what is the oldest and most effective chemical control agent?
iodine
mode of action of chlorine?
Inhibits cellular enzyme system
how do surfactants act to rid the body of microbes?
it attaches to pieces of dirt(microbes) and lift them off the surface, making them then able to be washed away
mode of action of heavy metals?
denature proteins
what are examples of heavy metals that KILL microbes?
silver
copper
zinc
what are two examples of oxidizing agents used to kill microbes?
peracetic acid
benzyl peroxide
what are two examples of aldehydes used to kill microbes?
formalin
glutaraldehyde
which chemicals act as sterilants?
peracetic acid
glutaraldehyde
written question what are the 4 factors that effect microbial death rate?
time of exposure
type of microbe
number of microbes
environmental factors (temp/pH/O2/organic material)
wq what are three parts of the cell that various control agents target/ kill/ inhibit in microbes?
plasma membrane (lysing cell)
proteins (enzymes)
nucleic acids (DNA/RNA)
wq how do surfactants act to rid the body of microbes?
(degerming agent) Surfactants act as an emulsifier that reduces surface tension between liquids, breaking apart any oily film into tiny drops with microbes attached, then being able to be rinsed/scrubbed off
