Class Note for MIC 205A at UA 3
Class Note for MIC 205A at UA 3
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This 9 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Arizona taught by a professor in Fall. Since its upload, it has received 20 views.
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Date Created: 02/06/15
Controlling Microbial Growth Chapter 11 Review Bacterial growth is increase in cell numbers Growth depends on temperature pH osmotic pressure oxygen and nutrients Log phase cultures are most sensitive to growth inhibition Generation Time Time required for cell to dividefor population to double Average for bacteria is 13 hours E coligeneration time 20 min 20 generations 7 hours 1 cell becomes 1 million cells Exponential Growth m i VinaHim Eymnunmll Exponential Growth in my my ir r rmer m cells Number my calls 1 a 2 lbl rim 7 Case Baby Caroline Flaccid paralysis Possible sources of infection Formula Honey Dirt Diagnosis infant botulism Microbe of the Week Clostridium botulinum Gram rod sporeformer lives in soil common in environment Spores ingested germinateand produce botulinum toxin Strict anaerobe Clostridium botulinum Exotoxin causes botulism accid paralysis Sources improperly honey canned produce Costridium botulinum toxin 0 Clinical use Botox Muscle spasms Excessive perspiration Wrinkles Control of Microbial Growth Terminology Sterilization destruction of aH forms of microbial life 0 Commercial sterilization sufficient heat to kill Clostridium botulinum endospores some nonpathogenic thermophilic bacteria may survive Disinfection destruction of vegetative pathogens on inert substances Terminology Antisepsis destruction of vegetative pathogens on living tissue Degerming mechanical removal of microbes from limited area Sanitization lowering microbial counts on eating and drinking utensils to safe levels Terminology Biocide or germicide kills microorganisms Fungicide kills fungi Virocide inactivates viruses 7 E g micrubmcides rm Hiy used lrl spermacides Bacteriostatic agent stops growth of bacteria Terminology Sepsis bacterial contamination Asegsis absence of signi cant contamination Aseptic technigue minimizes contamination Microbial Death Microbes die at a constant rate Factors affecting how long it takes to kill bacteria number ofmicrobes environment slowed by organic materials bio lms eg feces sewage hasten ed by prior cleaning heat Microbial Death Factors affecting how long it takes to kill bacteria time of exposure characteristics of microbes most resistant are spores thick lipid coats protozoan cysts Effect of Population Load on Death Curve Fig 71 High 009mm Vim mm Actions of Microbial Control Agents Alteration of membrane permeability Damage to proteins and nucleic acids Mutation Physical Control Methods Temperature Desiccation Osmotic pressure Radiation Heat Preservation Must know temperature and time needed to kill critical bacteria The thermal death time Moist Heat Coagulates proteins by breaking hydrogen bonds Boiling 10 minutes kills most pathogens hepatitis virus needs 30 minutes and spores need 20 hours Autoclave 15 psi for 15 minutes at 121 C psi pounds per square inch Pasteurization Used when taste of product would be damaged by longer heating lowers numbers of pathogens 63 C for 30 minutes Hightemperature shortterm HTST pasteurization 72 C for 15 seconds UHT sterilization 140 C for3 seconds Dry Heat Flaming Oven 170 C 2 hours Low Temperature Refrigeration is bacteriostatic Most pathogens do not grow Freezing slow freezing creates ice crystals Membrane Filtration Fig 74 Pore size controls which microbes are removed HEPA filters used in safety hoods and operating theaters Limiting Water 0 Desiccation bacteriostatic Review lyophilization used to preserve cultures 0 Osmotic pressure high concentrations of salt or sugar 0 Molds and yeasts most resistant Radiation Radiation Ionizing radiation gamma rays X rays high energy electron beams most energetic Ionization of H20 to form OH39 radicals 0 Cause mutations and death Radiation Li 0 Low level ionizing radiation used on spices certain meats and vegetables 0 High energy electron beams used for medical supplies UV Radiation Thymine dimers in DNA Germicidal lamps vaccine disinfection Not penetrating Can damage eyes GERMtCIDALuvLAMp nlinw Microwaves Very little effect on microbes Microwave ovens kill vegetative pathogens by heating Solid foods heat unevenly A good summary of physical methods in Table 115 Chemical Methods Disinfectants Surfaceactive agents surfactants Chemical food preservatives Aldehydes formaldehyde formalin Gas sterilization Oxidizing agents Disinfectants Phenols and phenolics damage lipid membranes Active m atter Stable in presence of organic Persist for long periods after Antibiotics application ON N G 00 Disinfectants Phenols mm WW I Orignially used by 39 4 E C39 Bisphenols Jojszhohffcrifs Hexachlopophene pHisoHex vapors during a on quot Ho cl and triclosan surgery c0120 Antiba cterial soaps and toothpaste Broad spectrum of activity Disinfectants Disinfectants Biguanides Chlorhexidine Halogens iodine and chlorine Low toxicity odine used in solution Used on skin and mucous Betadme and Isodme Chorine is a gas that forms membranes bleach hypochlorite in water Chloramines are chlorine and ammonia Disinfectants Evaluation of Disinfectants Fig 76 Alcohol protein denaturation and membrane damage evaporate quickly ethanol and isopropanol Heavy Metals Denature proteins silver nitrate topical cream mercuric chloride paint copper sulfate algicide zinc mouthwash paints Heavy Metals Surfactants Decrease surface tension damage Quaternary Ammonium Compounds Quats H H cHa lipid membranes i l 7 H l f H fir cum CI Soaps and detergents H H CH3 Quaternary ammonium compounds microbicidal mmmn mmmmm Chemical Food Preservatives Aldehydes Sulfurdioxide Sodium benzoate Sorbic acid Calcium propionate Sodium nitrate and sodium nitrite Formaldehyde formalin and glutaraldehyde Disinfect instruments Used to preserve tissues for pathology Crossink protein molecules Gas Sterilization Ethylene oxide Denatures proteins Kis a spores and microbes with lengthy exposure High penetration Oxidizing Agents Ozone Hydrogen peroxide Benzoyl peroxide Peracetic acid nterfere with metabolism especially of anaerobes m I Antiseptic Effectiveness V whmm Pavemnganlzadan my rm rm my mm summ a m mam1mm Mum mm mm mmm rwvmmwmeIm mum um Grummanu W mm wwmlwm Microbial Sensitivity to Chemical Biocides Fig 711 What You Should Know Terminology Types of physical and chemical control agents not speci c names Example of when each would be used
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