What criteria must be met in order for new medium to be accepted for use in microbial enumeration tests?
USP Chapter , Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests, lists the following acceptance criteria:
If testing agar, the number of colonies on the new batch of medium must be within a factor of two of the number of colonies on the previously approved medium. If testing broth, the new and previously approved medium must be comparable in appearance.