Lecture+14-Control+of+microbes

Tuberculosis no one an7microbial is perfect for every

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Unformatted text preview: educ7on Microbial death Under a given treatment, bacteria die at a constant rate What is the D value? 3 minutes = 103 cells/ml 4 minutes = 102 cells/ml D value = ? Factors that affect the D value •  Popula7on size •  Popula7on composi7on •  Intensity/concentra7on of agent •  Time of exposure •  Temperature •  Physical/chemical environment Larger the popula7on, longer the total 7me required to kill all the cells What about the D value? Popula7on Composi7on •  Microbes respond differently 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 Intensity/Concentra7on •  Concentra7on of an an7microbial agent can impact D value •  More concentrated = lower D value –  Up to a certain point –  Excep7on : Ethanol Intensity/Concentra7on •  “Gentle as water” •  > 99% water •  < 1% bleach –  (0.0095%) •  Spray un7l wet –  Let stand 2 min http://www.clorox.com/products/overview.php?prod_id=ahsds Intensity/Concentra7on •  Clorox Anywhere = 22 oz for $3.99 •  Clorox Bleach = 96 oz for $3.29 •  1 bohle of bleach = 459 bohles Clorox anywhere –  Pay $1831.41 for Clorox Anywhere Time of Exposure •  Most an7microbials need 7me to work eec7vely •  Recall the table and graph we looked at a few slides earlier Temperature •  Higher temperature usually increases an7microbial ac7vity •  Lower concentra7ons can ojen be effec7ve if used at a higher temperature •  Why? Physical/Chemical Environment •  What environmental factors affect microbial growth? –  pH, temperature, oxygen concentra7ons •  Heat is more effec7ve at...
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