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a process that removes and destroys all life forms
sterilization
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a process that usually kills pathogenic microbes, usually on inanimate objects
disinfection
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a chemical or physical agent that kills pathogens
may be sporocidal
disinfectants
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the inhibition of growth of microorganisms on living tissues
antisepsis
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a chemical agent that inhibits the growth of microbes, usually on living tissues
antiseptics
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a process of preventing purification or contamination
asepsis
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one that causes fairly prompt death (irreversible damage)
cidal agent
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one that causes inhibition of growth (reversible damage)
static agent
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a process that kills or removes 99.9% of growing bacteria for an object, usually eating utensils, dishes, etc.
sanitization
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a process in which both living pathogens & their toxic products are removed
decontamination
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careful tissue cleaning with an antiseptic
may reuse total bacterial population by thousand fold
replaces the term skin disinfection
degermation (degerming)
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a graphic representation of the death of a specific population number per interval of disinfection/sterilizatin time
log death curve
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the muber of microbes in an object to be treated
microbial load (bioburden)
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the temperature at which a given suspension of bacteria are killed in 10 minutes
thermal death point
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the shortest period of time required to kill a suspension of bacteria at a specific temperature under specific conditions
thermal death time
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the time required for 90% of microbes to be killed
disinfectant does not kill at equal rate
decimal reduction time (DRT)
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the effect of a 10o rise in temperature on the killing rate
temperature coefficient
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one of the most widely used techniques for killing or inhibiting microbes
temperature
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kills by:
1. denaturation/coagulation of cellular proteins/enzymes
2. altering the physical state of lipids (making membranes impermeable or leaky)
most effective
moist heat
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kills by:
1. oxidation of cell components
2. altering the physical state of lipids
dry heat
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1. usually inhibits growth but may kill cells by coagulation/denaturation of cellular proteins/enzymes
2. altering the physical state of lipids
3. decreased chemical reactions or metabolism
not relied on to sterilize
low temperature (refrigeration/freezing.lyophilization)
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what are the methods of sterilization?
- moist heat
- dry heat
- pasteurization
- low temperature
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what are the methods of moist heat sterilization?
- boiling water or free flowing steam
- autoclaving (steam under pressure)
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boiling water or free flowing steam
100oC for 15 minutes. effective against intesinal bacteria and other vegetative bacterial cells (killed in 10 mins), but not spores (can resist boiling for up to 10 hours). HBV (hepatitis B virus) is killed within 30 minutes. uses: dishes, basins, pitchers and various equipment such as dental hard pieces and carbon dental instruments
**pure water @ 1 atmosphere of pressure
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autoclaving
121oC at 15 pounds of pressure per square inch for 15-20 minutes. probably the most widely used sterilization technique. it is not the pressure that kills but the fact that the pressure raises the temperature of water above the boiling point. this creates steam which rapidly penetrates cells and spores coagulation cellular proteins and enzymes. uses: sterilization of microbiological media, terminal sterilization of cultures, solutions, syringes, needles and other instruments and objects that can withstand the temperature and pressure.
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what are methods of dry heat sterilization?
- direct flaming
- hot air (hot oven) sterilization
- incineration
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direct flaming
used on inoculation loops and transfer needles
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170oF-180oF for 2 hours. the time required for dyr sterilization is much longer because cellular components must oxidize. uses: glassware, mineral oil, Vaseline, waxes, powders and other material which must be kept dry or which will not allow water to penetrate. used in dental for cotton pellets and paper points
*mineral oil, Vaseline, powder should not get wet
*wax - does not get heated to the center in the autoclave
hot air (hot oven) sterilization
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used to sterilize contaminated paper products, dressings, cadavers, bags, wipes, anything that is disposable and no longer of value
incineration
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what are the methods of pasteurization?
- classic pasteurization
- HTST (high temperature short time)
- UHT (ultra high treatment)
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