Review Sheet for MIC 205A at UA
Review Sheet for MIC 205A at UA
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This 8 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 18 views.
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Date Created: 02/06/15
Controlling Bacterial Growth 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 Bacteria Undergo Exponen al Growth of cells Number of Growth measurements direct Plate counts detect viable organisms Direct microscopic counts detect total numbers Growth measurements Indirect Turbidity light absorption compared to a standard Metabolic activity amount of product produced in a given time Dry weight remove water and weigh YE335 7 r I y d 1 13 39339 1 139 4 l V 57 quot VA 1 VP Terminology Sterilization destruction of aH forms of microbial life Commercial sterilization sufficient heat to kill Clostridium botulinum endospores some nonpathogenic thermophilic bacteria may survive Disinfection destruction of vegetative pathogens on inert substances Microbe of the Day Clostridium botulinum Common in environment Clostridium botulinum Gram positive rod Forms spores Strict anaerobe 7 Clostridium botulinum Exotoxin causes botulism paralysis blocks nerve signals to muscles C botulinum Exotoxin Botox Used cosmetically to reduce wrinkles Used medically to relieve muscle spasm excessive production of sweat Terminology Antisepsis chemical destruction of vegetative pathogens on living ssue 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 Bacteriostatic agent stops growth of bacteria Terminology Sepsis bacterial contamination Asepsis absence of significant contamination Aseptic technique minimizes contamination Microbial Death Microbes die at a constant rate Factors affecting how long it takes to kill bacteria number of microbes environment slowed by organic materials biofilms hastened by 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 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 Must know temperature and time needed to kill critical bacteria Moist heat boiling autoclave Dry heat oven 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 121 C 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 for 3 seconds Dry Heat Flaming Oven 170 C 2 hours l Low Temperature Refrigeration is bacteriostatic Most pathogens do not grow Exception Freezing slow freezing creates ice crystals Membrane Filtration which microbes are removed in safety hoods and operating theaters Pore size controls HEPA filters used Limiting Water Desiccation bacteriostatic lyophilization used to preserve cultures Osmotic pressure high concentrations of salt or sugar Molds and yeasts most resistant Radiation 500 nm 550 rim 600 rim 550 nm lm 350 nm 400 NH 450 nm 230nm 295nm 330nm 700 nm Wavelength i u y i Copyrxghl 2001 llamamvn Cummmgs an imprinch Addison Wesley Lorlgman inc 750 n m Radiation Ionizing radiation gamma rays X rays high energy electron beams most energetic Ionization of H20 to form OH39 radicals gt mutations and death Low level ionizing radiation used on spices certain meats and vegetables High energy electron beams used for medical supplies UV Radiation Thymine dimers in DNA Germicidal lamps vaccine disinfection Not penetrating Can damage eyes aims Microwaves Very little effect on microbes Microwave ovens kill vegetative pathogens by heating Solid foods heat unevenly Chemical Methods m Disinfectants and antiseptics Killinhibit growth of microbes on Surfaceactive agents surfactants surfaces Chemicai food preservatives Phenols and phenolics damage lipid Aldeh des membranes y Active in presence oforganic matter Gas sterilization Stable Oxidizing agents Persist for long periods after Antibiotics application DisinfectantsAntiseptics Antiseptics Bisphenols Biguanides Chlorhexidine Hexachlorophene pHisoHex Low toxicity and trlClosan Used on skin and mucous Antibacterial soaps and membranes toothpaste Broad spectrum of activity Disinfectants Antiseptics Halogens iodine and chlorine Alcohol protein denaturation and lodine used in solution membrane damage Betadine and lsodine Chlorine is a gas that forms bleach hypochlorite in water emancl and S0pr0par10 Chloramines are chlorine and not effective if taken internally ammonia evaporate quickly Heavy Metals Surfactants Denature proteins silver nitrate topical Decrease surface tension Cream Soaps and detergents mercuric chloride paint Quaternary ammonium copper sulfate compounds microbicidal algaecide zinc mouthwash paints Chemical Food Preservatives Aldeh des Used in foods to inhibit microbial Formaldehyde formalin and growth glutaraldehyde Sumquot d39ox39de Disinfect instruments SOdilJm b nzoate Used to preserve tissues for Sorblc aCId pathology Calcium propionate Crosslink protein molecules Sodium nitrate and sodium nitrite Gas Sterilization Oxidizing Agents Ethylene oxide Ozone Denatures proteins Hydrogen peroxide Kills all spores and microbes with Benzoyl peroxide lengthy exposure High penetration Peracetic acid Interfere with metabolism especially of anaerobes Antiseptic Effectiveness 100 Soap and water 80 Equot so E z a m g 40 E n a w u s E 20 m a ID 0 20 40 60 so 100 120 Time sec Mosi RDSistanl Least Hesisiam Endospoves oi baciuna Mycohacteila Cysts oi pioiozoa Vegexalrve pmlazaa Gramnegain Dacleria Fungi including mosl lungal spore Iorms Viruses Wllhoui envelopes Grampmilivs Daniella viruses wuh lipid envelopes n ii kmillml iii mimiiwasw imam im Microbial Sensitivity to Chemical Biocides What You Should Know Terminology Types of physical and chemical control agents not specific names Example of when each would be used internal external inanimate objects
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