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Micro Chapt. 5
Control of Growth
Question | Answer |
---|---|
Decontamination | treated to REDUCE the number of disease-causing microbes to a level that is safe to handle. |
Most resistant forms of life | The endospores of Bacillus and Clostridium |
Moist heat | destroys microorganisms by causing the irreversible coagulation of their proteins - boiling does not kill spores |
Pressure cookers & autoclaves | heat water in an enclosed vessel that causes the pressure in the vessel to increase beyond atmospheric pressure, which kills endospores |
Dry heat | destroy microorganisms by oxidizing cells to ashes or irreversibly denatures their proteins. |
Dry heat v. wet heat | Dry heat takes much longer than wet heat to kill microorganisms |
Gluteraldehyde and formaldehyde | destroy microorganisms and viruses by inactivating proteins and nucleic acids. |
Chlorhexidine | a biguanide extensively used in antiseptic products. |
Gamma Rays for labware | cause biological damage by producing superoxide and hydroxyl free radicals. |
Irridiation | used to sterilize heat sensitive materials and to decrease the numbers of microorganisms in foods. |
FDA approved usage for irridation | insects in fruits, vegetables and grains, to destroy the trichina parasite in pork, and to control Salmonella and E. coli O157:H7 in meats. |
Filtration of liguids to control growth | filter with 2.0 micron pore size enough to keep bacteria out |
Air filtration | HEPA filters are used in specialized hospital rooms to protect patients who are exquisitely susceptible to infection. |
Osmotic pressure | adding salt to meat or sugar to jam keeps microbes from growing |
Why would the term "sterilization" not encompass prions? | The "organisms" cannot be destroyed by high heat. |
Would it be safe to say that if all bacterial endospores had been killed, than all other microorganisms had also been killed? | Yes. Endospores are killed only by temperatures higher than those sufficient to kill other microorganisms. So, if endospores are killed, then other microorganisms must have been killed. |
The D value refers to | the time for 90% of the organisms to die |
Steralants | destroys all microorganisms including endospores & viruses. 6 - 10 hour traetments |
High-level disinfectant | kills viruses & vegitative organisms but does NOT kill endospores |
intermediate disinfectant | does not kill viruses or spores |
Low-level (general purpose) disinfectants | destroys fungi, vegetative bacteria |
Biguanides | used in soaps & lotions and it persists on skin |
the amount of time that it takes at a certain temperature to kill 90% of the organisms being studied | D-value |
Ethylene oxide is a germicide that kills by reacting with | protiens |
What do germicidal agents act on? | membrane, protiens, DNA |
Commercial canning process | uses retort to kill spores of clostridium botulitis |
UV is used to sterilize: | air, drinking water, surfaces |
How does UV light sterilze? | damages DNA |
What does ionizing radiation not destroy? | endospores |
What can ionizing radiation destroy? | samonella and other gram negative forms. |
HEPA filters | remove nearly all microorganisms |
What do gamma rays do? | cause biological damage by producing superoxide & free radicals |
What are gamma rays used for? | to sterlize heat-sensitive materials & decrease microorganisms in food |
Factors effecting the selection of germicidal chemical | toxicity, residue,activity in presence of organic matter, compatibility, cost, storage, disposal |
causes irreversible coagulation of protiens to destroy organism | moist heat |
What is the hardest thing to kill w/ chemicals & heat? | endospores |
What concentration of alcohol is most effective? | 75% |