D-value (microbiology)

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In microbiology, D-value refers to decimal reduction time and is the time required at a certain temperature to kill 90% of the organisms being studied.

Thus after a colony is reduced by 1 D, only 10% of the original organisms remain, i.e., the population number has been reduced by one decimal place in the counting scheme. Generally, each lot of a sterilization-resistant organism is given a unique D-value. When referring to D-values it is proper to give the temperature as a subscript of the "D". For example, given a hypothetical organism which is reduced by 90% after exposure to temperatures of 300° F for 20 minutes, the D-value would be written as D300F = 20 minutes. D-value determination is often carried out to measure a disinfectant's efficiency to reduce the number of microbes present in a given environment.[1]

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  1. ^ Priscila Gava Mazzola, Thereza Christina Vessoni Penna, Alzira M da S Martins (17 October 2003). "Determination of decimal reduction time (D value) of chemical agents used in hospitals for disinfection purposes". BMC Infectious Diseases 3: 24. doi:10.1186/1471-2334-3-24.