Flashcards in chapter 9 Deck (97):
what is meant by microbial control?
reduction in number and activity.
how can you control growth microorganisms ?
1. killing microoirganisms
2. inhibiting growth of microorganisms
3. removing them
kills or removes all living microbes.
use of physical/chemical agents(disinfectants) to kill or destroy microbes
chemical agents to kill/destroy microbes in animate(living) objects
removal of microbes
disinfecting plates, utensils, and others used by the public
heating to a certain temp. to kill the most resistant bacteria.
ex: mycrobial tuberculosis (milk)
CANNOT KILL ENDOSPORES
what is microbial death?
-permanent loss of reproductive ability
-exponential (die gradually)
what are the mode of actions of antimicrobial agents?
-alteration of cell walls and membranes
-damage of proteins and nucleic acids
what are the characteristics of an ideal antimicrobial method-
-inexpensive *can be cheap but harmful.
what are the factors that affect the efficacy of antimicrobial agents?
-site to be treated(hospital or home)
-relative susceptibility of organisms(vegetative cells vs. endospores)
temp, pH, presence of organic matter
compare susceptibility of vegetative cells with endospores to antimicrobial agents.
endospores= inactive= very resistant
what is the effect of temp on the action of antimicrobial agents?
increase temp- hasten effect of microbial agent
what is the effect of pH on the action of antimicrobial agents?
heat is effective in acid than in alkali
increase temp = decreased pH
what are examples of organic matter that may affect the action of antimicrobial agent?
sputum, blood feces, urine
organic matter presence may lower the efficiency of antimicrobial agents
what is the effect of the presence of organic matter on the action of antimicrobial agents?
-inactivates the agent
-protects the microbes
-intervenes with the penetration of the agent
two methods of microbial control?
what is the mode of action of moist heat?
-denatures proteins and destroys cell membrane and cell wall
what are examples of methods to control microorganisms using moist heat?
-boiling=100 degrees C
what is an autoclave?
pressure arises, temp rises to kill moist resistant microbes
what happens to temp when pressure increases?
which kill the microorganisms, the high temp or the press?
what is the time-temp requirements of sterilization using autoclave?
121 degrees C
what is pasteurization?
-cannot kill endospores
process: historical pasteurization treatment: 63 degrees C for 30min
process: flash treatment: 72 degrees C 15 seconds
process: ultra-high temp treatment: 134 degrees C for 1 sec
antimicrobial agents that would damage the cell wall of bacteria will kill the bacterial because bacteria will....
be susceptible to lysis.
is moist head cidal or static method?
a-cidal.... = kills bacteria
what is the mode of action of dry heat?
oxidation, reduced into ashes
what are examples of method to control microorganisms using dry heat?
-complete incineration 1500 degrees C
-oven sterilization 1-2 hours at 160-170 degrees C
compare time and temp requirements of moist heat sterilization with dry heat sterilization.
**transfer of heat is faster in moist heat.
-temps are higher in dry heat but the process is slower.
explain why the temp is lower and time is shorter in moist heat than in dry heat sterilization ..?
bc the water helps to denature microbes faster... water heats up faster.
what is the mode of action of low temp to microbial growth?
stops & slows growth & decreases metabolism
what are examples of methods to control microorganisms using low temp?
-regrigerator: around 4 degrees C
-Freezer: ordinary freezer around -10 to -20 degrees C
ultracold lab freezer typically -80 degrees C
refrigeration and freezing is what type of method? static or cidal? why?
static, bc it only inhibits the growth of microbes
temps are important for food safety, what is meant by danger zone?
the zone of fastest growth.
what is the temp range in the danger zone?
60 - 4 degrees C
phycrophils can spoil food in the _____________, and mesophiles grow faster in ___________ _________.
what is dessication?
removal of water
how does desiccation control microorganisms?
action: inhibits the growth and disrupts metabolism
what are examples of dessication methods?
review hypertonic solutions.
what is water activity?
describes amount of water available for microbial growth.
differentiate water activity of food from moisture content of food...
water activity= free water; moisture content= free water& water bonded to other things.
water activity is expressed as ___________________________
aw or % equilibrium relative humidity(%ERH)
if the water activity of a certain food product is 0.4 what is the ERH?
what is the min. aw of the following microorganisms?
1. normal bac 5. xerophilic molds
2. normal yeast
3. normal molds 6. osmpohilic yeast
4. halophilic bac
1. 0.91 (fresh meats, milk)
2. 0.88 (dry cheese, sponge cake)
3. 0.80 (condensed milk, flour0
4. 0.75 (jam, marshmellows)
5. 0.65 (rolled oats)
6. 0.60 (dried fruits)
what is membrane filtration? used for?
physically removes (degerming) microbes-- used for liquid materials that can't be sterilized.
what are examples of equipment that use membrane filtration?
-** microbes will be retained in the filter paper
describe how a laminar flow biological safety cabinet works to control microorganisms...?
air moves away from the person, up & thru a filter & then back out.
what are the 4 levels of safety in labs dealing with pathogens?
1. bio safety level 1 = handling pathogens that don't cause disease in healthy humans.
2. bio safety level 2 = handling moderately hazardous agents
3. bio safety level 3- handling microbes in safety cabinets
4. bio safety level 4 = handling of microbes that cause severe or fatal disease.
what are examples of ionizing radiations? what are their modes of action?
* both cause damage to DNA and inhibits proteins
what is an example of non-ionizing radiations? what is its mode of action?
*cause damage to DNA and inhibits proteins
UV rays are __________ wave length, and ____________ energy.
what is the mode of action in microwave cooking?
-kills microbes **CIDAL
-denaturation of proteins due to heat generated
high level disinfectants/ and antiseptics kill _______________
intermediate level disinfectants/ and antiseptics kill ______________
low level disinfectants/ and antiseptics kill ________________
1. endospores and below
2. mycobacteria and below
3. trophozoites and below
what are the uses of phenol and phenolics?
intermediate- to low level disinfectants
what are examples of phenols and phenolics ??
lysol, triclosan, cresols
how do phenols and phenolics control microorganisms?
denatures proteins and disrupts cell membrane
*remain effective in organic contaminants
what are uses of alcohol?
what are examples of alcohol?
isopropyl alcohol (70%-90%) tinctures
how do alcohols control microorganisms?
denature proteins and disrupt cytoplasmic membrane.
alcohols are effective against what microbes? can alcohol kill endospores?
bacterialcidal, fungicidal, virocidal, & cannot kill endospores.
what is more effective in killing microorganisms? alcohol diluted with water or undiluted alcohol? explain.
70% is more effective bc water denatures proteins(or helps)
what are examples of halogens?
iodine, chorine, bromine, fluorine
what are the uses of halogens?
intermediate-level disinfectants and antiseptic chemicals.
how to halogens kill microorganisms?
damage enzymes by oxidation or denaturation
what is tincture?
mixture of water and alcohol
what is an iodophor?
iodine-containing organic cpd
ex: betadine= used for surgery and injection
what forms of chlorine are used to control microorganisms?
-Na/Ca hypochlorite (house bleach)
-ClO2 (disinfect building, ex: 9/11)
-Chloramine (disinfect water)
why is bromine usually used in hot tubs?
bc bromine evaporates more slowly in higher temps, and last longer
what are examples of oxidizing agents?
peroxides, ozone, and per-acetic acid (sterilant)=sterilizes food utensils.
what are the uses for oxidizing agents?
how do oxidizing agents kill microorganisms?
oxidation of cell structures and enzymes
what oxidizing agent is used to clean deep wounds ?
what oxidizing agent is used to disinfect water?
ozone (O3) - not antiseptic
what oxidizing agent is used to sterilize food processing equiptments?
sporocide- kill bacterial endospores
what are surfactants ?
reduce surface tension
what are examples of surfactants?
-soaps (degerming agents)
quats- benzalkonium chloride, cetylpyridinium chloride
what are the uses for surfactants ?
how do surfactants control microorganisms?
disrupts cell membranes
what are examples of heavy metals?
Zn, Hg, Ag, Cu
what are the uses of heavy metals?
low-level bacteriostatic, fungistatic agents
*static= inhibits growth
how do heavy metals kill microorganisms?
denatures proteins and interferes with S groups in proteins.
what heavy metal is used to treat ophthalmic gonorrhea ?
1% Soln AgNo3- silver nitrate
what heavy metal is used to treat burns?
what heavy metal is used to kill algae in swimming pools?
CuSo4- copper sulfate - algicide=kill
what are examples of gaseous agents?
ethylene oxide, propylene oxide, B propiolactone
what are the uses of gaseous agents?
in closed chambers to sterilize items (bed, pillows)
how do gaseous agents kill microorganisms?
denatures proteins and DNA by cross-linking functional groups
what are the methods used to evaluate the efficiency of disinfectants and antiseptics? describe each...
-kelsey-sykes capacity test(standard method in european countries)
-in-use test (most effective)
-disk-diffusion method:filter paper, zone of inhibiton...
zone of clearing = ?
examples of in-use test
control: counter without backdown
treated: counter with backdown
tincture of iodine =?