the killing or removal of all microorganisms in a material on on an object
sterilization
means there are no living organisms in or on a material
sterility
reducing the number of pathogenic organisms on objects or in materials so that they pose no threat of disease
disinfection
agents typically applied to inanimate objects
disinfectants
agents applied to living tissue
antiseptics
what are the 3 prinicples of the control of microbial growth
1) a definate proportion of the organisms die in a given time interval
2) the fewer organisms present, the shorter the time needed to achieve sterility
3) microorganisms differ in their susceptibility to antimicrobial agents
bacteria killing
bactericidal
bacterial growth inhibiting
bacteriostatic
a numerical expression for the effectiveness of a disinfectant relative to that of phenol
phenol coefficient
when did Lister introduce phenol (carbolic acid) as a disinfectant?
1867
method of evaluating the antimicrobial properties of a chemical agent using filter paper diskc placed on an innoculated agar plate
filter paper disk method
a method of evaluating the antimicrobial properties of a chemical agent using standard preparations of certain test bacteria
use-dilution test
what 6 qualities should be considered in deciding which disinfectant to use
1) be fast acting even in the presence of organic substances, such as those in body fluids
2) be effective against all types of infectious agents without destroying tissue or acting as a poison if ingested
3) easily penetrated material to be disinfected without damaging or discoloring the material
4) be easy to prepare and stable even when exposed to light, heat, or other environmental factors
5) be inexpensive and easy to obtain and use
6) no unpleasant odor
althoug the kinds of reactions are almost as numerous as the agents themselves, agent can be grouped together by what they affect _, _, and _.
proteins
membranes
other cell components
alteration of protein structure
denaturation
soluble compounds that reduce surface tension, just as soaps and detergents break up grease particles in dishwater and include alcohols, detergents, and quaternary ammonium compounds.
surfactants
often used with other chemical agents to help the agent penetrate fatty substances
wetting agents
Alkylating agents such as ethylene oxide, nitrous acid, and hydroxylamine, act as chemical mutagens altering _ or _.
DNA or RNA
what is selenium used in
head and shoulders
what is used in the eyes of newborns to prevent gonococcal infections
silver nitrate
what is merthiolate and mercurochrome used for
to disinfect skin wounds
what is tincture
an alcoholic solution
what are chlorine and bromine
halogens
what solution is better 70% alcohol or 99% alcohol
70% is better
does alcohol sterilize or disinfect skin
alcohol disinfects but does not sterilize skin because it evaporates quickly and stays in contact with microbes for only a few seconds
what are lysol, cresols (creosote), hibiclens
Phenols
what is hydrogen peroxide
oxidizing agent, oxygen kills the obligate anaerobes present in the wounds. Good for puncture wounds
disrupts both the proteins and the nucleic acids. i.e. formaldehyde, ethylene oxide
alkylating agents
what are the specific chemical antimicrobial agents we talked about in class
soaps and detergents
acids and alkalis
heavy metals
halogens
alcohols
phenols
oxidizing agents
alkylating agents
dyes
other agents
what are some of the other agents that have microbial effects
sodium nitrite, antifreeze, certain plant oils like thymol, eugenol, sulfites, sulfur dioxide, sodium diacetate, garlic onions
the temp that kills all the bacteria in a 24-hour-old broth culture at neutral pH in 10 minutes
thermal death point
the time required to kill all the bacteria in a particular culture at a specified temp
thermal death time
the length of time needed to kill 90% of the organisms in a given population at a specified temp
decimal reduction time - AKA DRT or D value
what are the types of applications/antimicrobial agents used to kill bacteria or slow the growth
dry heat
moist heat
pasteurization
refrigeration
freezing
freeze-drying
radiation
sonic and ultrasound waves
filtration
osmotic pressure
what is the #1 way to sterilize
dry direct heat
uses pressure and temp to sterilize. i.e. autoclave
moist heat
what 2 rules must be followed with an autoclave
1) articles must be placed in the autoclave so that steam can easily penetrate them
2) air should be evacuated so that the chamber fills with steam
pasteurization is not, is not, is not a form of
sterilization
what are the methods that can be used in pasteurization
flash method - up to 71.6C for 15 seconds
holding method - 62.9C for 30 minutes
what is ultrahigh temperature processing (UHT)
raises the temp from 74C to 140C and then drops it back to 74C in less than 5 seconds
slows the growth of bacteria and helps prevent spoiling of foods
refrigeration
stops bacterial growth for the time being
freezing
the removal of water inhibits the action of enzymes and preserves foods
drying
the drying of material from the frozen state
lyophilization
what are the 4 types of radiation used
UV light - most effective in killing microorganisms by damaging DNA and proteins
Ionizing radiation - x-rays and gamma rays
Microwave radiation - only useful when heating items that contain water
strong visible light - sunlight has bactericidal effects
with sonic and ultrasonic waves what are cavitation and sonication
cavitation is the formation of a cavity inside the cytoplasm of a cell
sonication is the disruption of cells by sound waves
the passage of materials through a filter or straining device
filtration
thin disks with pores that prevent the passage of anything larger than the pore size
membrane filters
high concentrations of salt, sugar, or other substances create a hyperosmotic medium which draws water from the microorganisms by _.
osmosis
loss of water, severely interferes with cell function and eventually leads to cell death
plasmolysis
germicidal
kills microbes
viricidal
inactivates viruses
bacteriocidal
kills bacteria
bacteriostatic
stops bacterial growth
sporicidal
kills bacterial endospores and fungal spores
fungicidal
kills yeasts and molds
Which term is used to describe the reruction in number if pathogenic organisms on objects or in material so that they do not pose a disease threat:
B) disinfection
true or false
when something is sterilized, there are levels or degrees which are reached for that object's or material's sterility.
false
Which of the following is true of the phenol coefficient test?
E) all of the above
surfactant damages
membrane lipid disruption
alkylating agents damage
protein denaturation
nucleic acid alteration
oxidation agents damage
protein denaturation
detergents damage
membrane lipid disruption
hydrolyzing agents damage
protein denaturation
heavy metals damage
protein denaturation
crystal violet dye damage
cell wall formation
refrigeration, freezing, drying, and freeze-drying _ the growth of microorganisms but does not usually _ them. Dry heat, moist heat under pressure, and open flame are much more effective in killing microbes by _ proteins, melting _, and incineration.
retard
kill
denaturing
lipids
The pasteurization process does which of the following to milk:
B) it kills microbial pathogens that might be present in milk
true or false
the advantage of UV-radiation disinfection is that it readily penetrates through most samples.
false
which of the following are reasons ehy UV light might be expected to be less effective in killing bacteria:
C) UV light cannot penetrate glass, cloth, paper, or most materials under which microbes might be located
gamma rays and x-rays are effective in killing microorganisms because they:
D) all of these
quaternary ammonium compounds (quats) are a type of:
B) alkylating agent
the active antimicrobial ingredient in bleach is:
D) hypochloride
what are phenol derivatives used for
instrument disinfection
skin disinfection
what is iodine used for
skin disinfection
what are alcohols used for
skin disinfection
what are acids used for
food preservation
what is chlorine used for
water disinfection
what are oxidizing agents used for
puncture wound disinfection
what are nitrates used for
food preservation
heat-sensitive materials (rubber and plastic) and bulky materials (mattresses) can be sterilized using:
E) gaseous ethylene oxide
true or false
In the process of autoclaving it is the increased temperature and not the increased pressure that kills all microbes including spores and the nucleic acids of viruses.
true
the minimum time used for sterilization by autoclaving is:
B) 15 min
which of the following is a limitation of the autoclave:
E) use with heat sensitive material
the recommended method for testing that an autoclave has truely sterilized a load uses:
D) bacillus stearothermophilus
microwave ovens will only heat materials that contain:
D) water
what does a researcher have to do in order to kill all bacteria in a liquid without damaging heat-labile proteins in the solution:
B) pass the liquid through a 0.22um filter
a few bacteria can fit through the 0.45um filter
most bacteria is 1.2um filter
how does the presence of high concenrations of salt or sugars in food prevent growth of microorganisms:
C) it sets up an enviroment high in osmotic pressure resulting in cellular plasmolysis (water loss)
how does the process lyophilization work in order to preserve microorganisms:
A) rapidly frozen organisms in vials are subjected to a vacuum instrument that removes water from them and seals the vials under vacuum
which of the following effects the elimination bacteria from an object:
E) all of the above
sensitivity is shown on the kirby-bauer method by a _
large zone of inhibition
a resistance is shown in the kirby-bauer method by a
small zone of inhibition or no zone at all
why are the resistant and sensitive zones different and not standard
some chemical agents my have molecules that are able to travel faster or farther through agar than other agents
