Lecture+14-Control+of+microbes

Lecture+14-Control+of+microbes - Control of microbes Recall...

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Control’of’microbes’
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Bacteria’require’certain’growth’condi7ons’ Temperature’ Nutrients’ Water’(osmo7c’balance)’ Appropriate’atmosphere’ pH’ Recall’from’lecture’on’growth’and’ nutri7on’
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What’is’one’way’to’control’microbial’growth?’ Make’their’growth’environment’unsuitable’ Slow’down’growth’to’prevent’food’spoilage’ Control’infec7on’ Control’of’microbial’growth’
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Bacteriosta7c’:’stops’bacterial’growth’ Sta7c’or’-’stasis’=’standing’s7ll’ Stops’growth,’doesn±t’kill’ Bactericidal’:’kills’bacteria’ cide’=’kill’ Sterilize’:’kill’all’forms’of’life,’including’endospores’ Also’inac7vates’viruses’ Some’terms’
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Disinfectant’:’kills’vegeta7ve’cells’only’ Usually’applies’to’inanimate’objects’ An7sep7c:’disinfectant’safe’for’animate’object’ Ex:’skin’ Sani7ze:’reduce’microbial’popula7on’to’a’safe’ level’ Ex:’Pasteuriza7on’ Some’terms’
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Microbes’and’biocides’
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Death’of’a’microbe’=’loss’of’the’ability’to’grow’ and’reproduce’ Inadequate’deFni7on’of’microbial’death’ An7microbial’agents’do’not’kill’instantly’ Microbes’die’over’a’period’of’7me’ Death’expressed’as’decimal’reduc7on’7me’ Microbial’death’
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D’value’ Defni7on:’the’7me’required’to’kill’90%’oF’the’ microbes’or’spores’in’a’sample’under’the’ specifed’condi7ons’ Reduc7on’in’one’log’or’ten-Fold’reduc7on’ Decimal’reduc7on’7me’
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Under’a’given’treatment,’bacteria’die’at’a’constant’rate’ Microbial’death’
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What’is’the’D’value?’ 3’minutes’=’10 3 ’cells/ml’ 4’minutes’=’10 2 ’cells/ml’ D’value’=’?’
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Factors’that’afect’the’D’value’ Popula7on’size’ Popula7on’composi7on’ Intensity/concentra7on’o±’agent’ Time’o±’exposure’ Temperature’ Physical/chemical’environment’
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Larger’the’popula7on,’longer’the’total’7me’required’to’ kill’all’the’cells’ What’about’the’D’value?’
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Popula7on’Composi7on’ Microbes’respond’diferently’to’an7microbials’ Spores’ M. tuberculosis No’one’an7microbial’is’perFect’For’every’organism!’ Mixed’bacterial’popula7ons’are’harder’to’kill’than’ popula7ons’composed’oF’a’single’species’
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Intensity/Concentra7on’ Concentra7on’of’an’an7microbial’agent’can’ impact’D’value’ More’concentrated’=’lower’D’value’ Up’to’a’certain’point’ Excep7on’:’Ethanol’
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Intensity/Concentra7on’ Gentle’as’water >’99%’water’
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Lecture+14-Control+of+microbes - Control of microbes Recall...

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