Description

This laboratory method for the detection of microorganisms in fuels corresponds to standard IP 385/19: "Enumeration of living microorganisms in middle distillates and their associated waters. Filtration and culture method".

This standard describes two methods A and B for the enumeration of germs in middle distillates.

Method A enables counts in middle distillates of up to 50,000 Colony Forming Units (CFU)/L for molds, and up to 100,000 CFU/L for bacteria and yeasts.

After filtration of a known volume of fuel through a membrane filter, the filters are placed directly on nutrient agar plates.

Method B is used to count aerobic micro-organisms in the aqueous phase associated with fuel. It is valid for counts of up to 5,^{108 CFU/ml}for molds and 1,¹⁰⁹ CFU/ml for bacteria and yeasts separately.

After separation of the aqueous phase, successive dilutions are made and then inoculated directly onto nutrient agars.