Microbiology 130
R.L. Brashear-Kaulfers

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Disinfectants-applied to inanimate objects
Antiseptics- applied to living tissue
Some can be used as both
Sterilization- killing or removal of all microorganisms in a material or on an object
Sterility- no living organisms on/in object
Disinfection- reducing the # of pathogenic organisms on object or in material, so they pose no threat of disease

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1out of 1 million probability is sterile
1)Total # of microbes present affects the length of time needed to eliminate them
2) Fewer organisms present, shorter time needed for sterility
Different microbial agents affect differently
Most susceptible phase is logarithmic phase
3) Microorganisms differ in their susceptibility to antimicrobial agents

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Potency or effectiveness of Chemical
Agents:
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Bactericidal- killing
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Bacteriostatic- growth inhibiting
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Ethyl and isopropyl alcohol- 70% effective as it can penetrate more deeply

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* Phenol coefficient- compare to phenol (carbolic acid) =1 higher is more effective, lower is less effective
Use with Staph typhi and Staph aureas standards
Used to research new disinfectants, but has problems
* Filter Paper Method- uses small filter disks
And look for zone of inhibition-shows some effectiveness but organic matter may interfere with results
* Use-Dilution test: standard prep of bacteria , coated on stainless steel and dipped into dilutions of agents, incubated and observed for no growth* better results than phenol test

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1) Should be fast acting in presence of organic substances
2) Be effective against all types of infectious agents without destroying tissue or acting as a poison if ingested
3) Easily penetrate material to be disinfected, without damaging/discoloring it
4) Be easy to prepare, stable when exposed to light, heat or other environ-mental factors
5) Be inexpensive, easy to obtain and use
6) Not have an unpleasant odor

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Reactions that affect proteins: denaturation by mild heat, acid, alkali destroys /alters protein
Reactions that affect membranes: protein and lipids- surfactants such as soaps and detergents
Do not kill but allow agents into membranes
Reactions that affect cell components: nucleic acids and energy production- lactic acid inhibit fermentation and energy production in bacteria and molds
Reactions that affect viruses: alkylating agents affect DNA or RNA

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Soaps and detergents: remove microbes, oily deposits and dirt, detergent-cationic (+)(food utensils), or anionic (-) laundry and household cleaners
Quats have amonium disinfectants: BAK, mouthwash
Acids and Alkali: soap is a mild alkali, acid preservatives retard mold growth in breads, margarine, soft drinks
Heavy Metals: selenium, mercury, copper, silver can inhibit bacterial growth such as silver nitrate and mercurochrome and merthiolate -tincture w/alcohol, selenium sulfide kills fungi and spores (dandruff shampoo)
Copper sulfate- kills algae in pools

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Halogens: Hypochlorous acid Cl, I, Br, Cloramine
Alcohols: denature proteins, skin antiseptics
Phenols: disrupt cell membranes
Oxidizing Agents:H
2
O
2 disenfectant
Alkylating Agents: disrupt nucleic acids and protein structures, may cause cancer, formaldehyde, ethylene oxide, glutaraldehyde
Dyes: acridine and methylene blue, crystal violet
Other Agents: plant oils for thyme and clove, nitrates, sulfites, sodium nitrate ( p 338)

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Heat- thermal death point-temperature
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DRT or D value-time needed to kill 90% of organisms
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Dry Heat- oxidizes molecules, used for metal objects and glassware, oils and powders. Dry heat penetrates more slowly
171C for 1 hr, 160 C for 2 hrs or 121 C for
16 hrs

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Moist Heat- widely used
Autoclave at 15 lb/in pressure for 15-20 minutes, temp at 121C to kill spores
Hospital autoclave called prevacuum autoclave, less time to sterilize
Pasteurization - kills pathogens, but not sterile milk = 71.6 C for 15 sec (flash method), or heat at 92.9 C for 30 min (holding method)
UHT-ultrahigh temp 74-140-74C in 5 sec used to make coffee creamers

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Refrigeration- foods 5C , Clostridium produce lethal toxins in frig spores
Freezing- -20C, preserve foods on home and industry, slows rate of microbes so they do not spoil food. Frozen foods should not be thawed and refrozen
Drying- absence of water inhibits enzymes, so it will preserve foods, drying clothes in dryer or in sunshine can destroy pathogens
Freeze-drying- lyophilization is drying from a frozen state to make instant coffee, to preserve cultures of microbes

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UV-ultraviolet light-40-390nm 200nm is most effective wavelength for killing by DNA dimers,
UV light for sewage treatment in some areas
Ionizing radiation- X rays and gamma rays, .1-
40nm very short
Microwave radiation-long wavelengths 1mm-1m
Strong visible light- sunlight, 400-700nm due to
UV

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Sonic and Ultrasonic waves-
Filtration- passage of material through a filter, use millipore -membrane filters 25um
Microbes on filter can be transferred to agar
(p346)
HEPA filters- clean air and capture microbes
Osmotic Pressure- plasmolysis or loss of water occurs with high concentration of salt, sugar used in jellies, syrup, pickles (p 347)