microb_control-1 - 1/01 MICROBIAL CONTROL Answer questions...

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1/01 MICROBIAL CONTROL Answer questions on work sheet. Terminology A. Sterilization - kills all microbes present B. Disinfection - reduces the number (control) of pathogens C. Sanitization - reduction in number of microbes present to safe (accepted) levels D. Two types of methods of microbial control 1. Physical methods 2. Chemical methods Physical methods A. Heat 1. Most common method, effective, least expensive 2. Denatures (coagulates) cell proteins (enzymes) 3. Two forms: moist heat, dry heat B. Moist heat methods 1. Boiling a. 98 -100 ° C/10 min. b. Inactivates most vegetative cells, not heat-resistant forms c. Drinking water, canning jars, etc. 2. Autoclave - steam under pressure, temperature steam a. 15# pressure/121 ° C/15 - 20 min. b. Destroys all forms - sterilization c. In addition to coagulating proteins, causes hydrolysis d. Media, surgical instruments, etc. 3. Pasteurization a. Heat material, holding at specific temperature for specific length of time, cool rapidly b. Low Temperature Long Term (Holding) method: 62 ° C for 30 min. c. High Temperature Short Term method: 72 ° C for 15 sec. d. Ultrahigh Temperature method: 140 ° C/15 sec.; 149 ° C/0.5 sec. e. Inactivates pathogens, reduces total microbial population f. Does not sterilize f. Dairy products, wine, beer, etc. C. Dry heat methods 1. Hot air ovens a. 160 - 170 ° C/2 - 3 hrs. b. Causes oxidation of microbes, sterilizes c. Used when moisture undesirable - glassware, metals, powders or petroleum-based products (oils). 1
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1/01 2. Incineration a. Burning - oxidation b. Must be complete c. Regulations to control release of ashes, odor d. Used to destroy disposable items, soiled dressings, tissue specimens. e. Flaming loop, tubes - form of incineration D. Filtration 1. Solids physically separated from liquids by passage through filters with extremely small pores (porcelain, ground glass, diatomaceous earth, asbestos, sand, membrane filters) 2. Liquids mechanically forced or pulled through (using a vacuum) filters which trap microbes 3. Does not sterilize unless pore size small enough to trap all organisms 4. Uses: materials (media, medications) that can't be heated, beer and wine, swimming pools and spas, sewage, air, testing water or air for organisms or allergens E. Radiation 1. Two types commonly used a. Ionizing rays (X-rays, gamma rays) b. Nonionizing rays (UV light) 2. Cause lethal changes in DNA, denatures proteins (produces hyperactive ions and free radicals) 3. UV light a. Of limited use, cannot penetrate materials (cloth, glass, paper, etc.) b. Used to reduce number organisms in air, on clean surfaces 4. Gamma rays, X-rays a. More effective, can penetrate materials b. Used to sterilize plastics, medications, foods (retards spoilage) F. Methods used for preservation 1. Increased osmotic pressure a. High concentrations of salt, sugar b. Dehydrates cells, more effective against bacteria than fungi c. Use: food preservation
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This note was uploaded on 10/18/2011 for the course MCB 3020 taught by Professor White during the Spring '09 term at University of Central Florida.

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microb_control-1 - 1/01 MICROBIAL CONTROL Answer questions...

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