USP Method <61>: Microbial Limit Test

The USP <61> test provides enumeration of mesophilic bacteria and fungi that may grow under aerobic conditions. This test provides the total number of aerobic organisms, yeast, and mold present within a sample. The sample is typically diluted, plated, and then incubated. Microbial enumeration of the sample can be achieved by membrane filtration, pour plate, surface spread, or the Most Probable Number (MPN) methods. Short-hand abbreviations for USP <61> testing may be encountered as follows: