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Micro Chapt. 5

Control of Growth

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%
Created by: sloanie32