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Disinfection
- destruction of most microorganisms and viruses on non living tissue
- (majority of germs in-animated)
- ex: phenolics, alcohols, aldehydes, soaps
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Aseptic
- an environment or procedure free of contamination by pathogens
- ex: preparation of surgical field; hand washing; flame sterilization of laboratory equipment
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Antisepsis
- reduction in the number of microorganisms and viruses, particularly potential pathogens on living tissue
- (major of germs animated)
- ex:iodine, alcohol
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-cide
-cidal
- kill
- ex: bactericide, fungicide, germicide, virucide
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degerming
- removal of microbes my mechanical means
- ex: handwashing, alcohol swabbing at site of injection
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Pasteurization
- use of heat to destroy pathogens and reduce the number of spoilage
- microorganisms in food and beverages
- ex: pasteurized milk and fruit juices
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Sanitization
- removal of pathogens from objects to meet public health standards
- ex: washing tableware in scalding H2O in restaurants
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Sterilization
- destruction of all microorganisms and viruses in or on an object
- ex: preparation of microbiological culture media and canned food
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-stasis
-static
- STOP
- ex: bacteriostatic, fungistatic, virustatic
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Microbial Death Rate
- -permanent loss of reproductive ability under idea environmental conditions
- -constant
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Bacteriostatic
stop growth
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Bactericidal effect
kills
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Antimicrobial Agents
- -alteration of cell walls and membranes
- -when damaged,effects of osmosis cause cells to burst
- -membrane controls passage of chemicals into and out of the cell
- -when damaged, cellular contents leaks out
- -damage to proteins and nucleic acids
- -protein function depends on 3D shape
- -extreme heat or certain chemicals denatures proteins
- -chemicals, radiation, heat can alter or destroy nucleic acid
- -produce fatal mutants
- -halt protein synthesis through action on RNA
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Relative susceptibilities of microbes to antimicrobial agents
- Strong antiseptic agent
- -prions
- -mycobacteria
- -cysts of protozoa
- -active stage protozoa (trophozoites)
- Intermediate Antiseptic
- -most gram negative bacteria -fungi -nonenveloped viruses
- -most gram positive bacteria
- -enveloped viruses
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Boiling
- -kills vegetative cells of bacteria and fungi protozoan trophozoites and most viruses
- -time critical
- -endospores, protozoan cysts and some viruses can survive
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Autoclaving
- -pressure applied to boiling H2O prevents steam from escaping
- -temp increase pressure increase
- -conditions: 121C, 15PSI, 15 min
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Moist heat
- -used to disinfect, sanitize,sterilize, and pasteurize
- -denatures proteins and destroys cytoplasmic membranes
- -more effective than dry heat
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Methods of microbial control
- 1. boiling
- 2. autoclaving
- 3. pasteurization
- 4. ultra high temp sterilization
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pasteurization
- -used for milk, ice-cream, yogurt, juices
- -not sterilization
- -heat tolerant microbes survive
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Ultrahigh temperature sterilization
- -140C for 1 to 3 seconds, then rapid cooling
- -treated liquids can be stored at room temp
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Most heat treatments of milk
- 1. historical (batch) pasteurization- 63C for 30 min
- 2. flash pasteurization- 72C for 15 sec
- 3. ultra high temp pasteurization- 135C for 1 sec
- 4. ultra high temp sterilization-140 C for 1-3 sec
- ex: coffee
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Dry heat
- -incineration (ultimate means of sterilization)
- -denatures proteins and oxidizes metabolic and structural chemicals
- -requires higher temp for longer time than moist heat
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Ionizing radiation
- -wavelength shorter than 1nm
- -electron beams, gamma ray, xray
- -ions disrupt hydrogen bonding, oxidize double covalent bonds, and create hydroxyl radicals
- - electron beams- effective at killing microbes but do not penetrate well
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X rays
- -require long time to kill microbes
- -not practical for microbial control-
- not usually for sterilization weaker than gamma rays
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Gamma rays
- -sterilize
- -penetrate well but require hours to kill microbes
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Non ionizing radiation
- -wavelength greater than 1nm
- -excites electrons, causing them to make new covalent bonds
- -affects 3D structure of proteins and nucleic acid
- -UV light causes pyrimidine dimers in DNA
- -UV light doesn't penetrate well
- ex: airconditioning
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Tdimer
when DNA sticks together from UV lights; next generation can't reproduce
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Alcohols
- -soap+alcohol=degerming
- -intermediate level disinfectant
- -denature proteins and disrupt cytoplasmic membranes
- -more effective than soap
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Halogens
- -iodine
- -chlorine
- -bromine
- -fluorine
- -intermediate level antimicrobial chemicals
- -damages proteins by denaturation
- -used for wound care
- -antiseptic
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Oxidizing Agents
- -peroxides
- -ozone
- -peracetic acid
- -kill by oxidation of microbial enzymes
- -hydrogen peroxide can disinfect and sterilize surface
- -not useful for treating open wounds because of catalase activity
- ozone= treatment of drinking H2O
- peracetic acid- effective sporicide used to sterilize equipment
- silver nitrate= wound care
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Heavy Metals
- -antiseptic
- -antibacterial
- -denature proteins
- -low level bacteriostatic and fungistatic agents
- -1% silver nitrate once used to prevent blindness cause by N. gonorrhoeae
- Thermerosal-preserve vaccines
- Copper- algal growth
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Enzymes
- -antimicrobial enzymes act against microorganisms
- -human tears contain lysozyme
- -nasal/mucous discharge
- lysozyme- digests peptidoglycan cell wall of bacteria, reduces # of bacteria in cheese
- prionzyme- remove prions on medical instruments
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Filtration
- -chemical process to get rid of germs
- -degerming
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Prions
- -cant be destroyed by autoclaving
- -tougher than endospore
- -not as wide spread in the world
- -NaOH (base) deactivates the prions
- HARDEST TO KILL
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Flu Virus
- -envelope virus
- -easiest to be killed
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