Microbial validation and release testing in industry often utilises commercially prepared stocks of standard test organisms to perform growth promotion (GP) tests. These preparations consist of a defined number of colony forming units (CFU) of the specific species maintained in lyophilised pellets or another stabilised format. Such preparations exhibit acceptable performance during their use in compendial methods (e.g. spread plate testing). This results as the CFU have sufficient time to pass from the lag phase into exponential growth, and thus develop into visible colonies for enumeration.
Rapid microbial testing systems are now available that drastically reduce the time-to-result for the analysis of test samples. With a shorter time-to-result, any variation in the duration of the lag phase of the test organism CFU may result in a perceived undercount of the CFU present in the sample.
This would occur as all the organisms may not have reached a sufficient colony size for detection by the Rapid Microbial Method (RMM) at the end-point of the test. Commercial preparations are presumed to grow as well as those samples prepared in-house; however, their relative growth performance has not been compared previously. This study examined the growth promotion of a suite of USP recommended QC test organisms obtained from three vendors compared with an in-house culture made at Rapid Micro Biosystems (RMB).
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