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30 maj 2018 · Calculation of D - Value, Z - Value and F0 - Value for sterilization in autoclave used for microbiology analysis as per USP and BP.
A D-value can be thought of as a mass division diameter. It is the diameter which, when all particles in a sample are arranged in order of ascending mass, divides the sample's mass into specified percentages. The percentage mass below the diameter of interest is the number expressed after the "D".
D-value is the time required to kill 90% of the spores or vegetative cells of a given microorganism at a specific temperature in a specific medium. D-values can be determined from survivor curves when the log of population is plotted against time, or by the formula: D reference temperature = Time/ (Log a -Log b)
In microbiology, in the context of a sterilization procedure, the D-value or decimal reduction time (or decimal reduction dose) is the time (or dose of an antimicrobial drug) required, at a given condition (e.g. temperature) or set of conditions, to achieve a one-log reduction, that is, to kill 90% of relevant microorganisms. [1]
A D-value at one temperature, along with a z-value, is used to define the heat resistance of a microorganism. z-Value: This is the temperature increase required to reduce the thermal death time by a factor of 10. It is the number of degrees between a 10-fold change (or log cycle) in a microorganism’s heat resistance.
17 paź 2003 · The highest D-values for various bacteria were determined for the following solutions: (i) 0.1% sodium dichloroisocyanurate (pH 7.0) – E. coli and A. calcoaceticus (D = 5.9 min); (ii) sodium hypochlorite (pH 7.0) at 0.025% for B. stearothermophilus (D = 24 min), E. coli and E. cloacae (D = 7.5 min); at 0.05% for B. stearothermophilus (D = 9.4 ...
D-values rely on modelling all particles as spheres. This is convenient when the majority of particles in a sample are relatively close to spherical in shape, but can cause problems when equivalent diameters must be used for more arbitrarily shaped particles.
