Clarifications on the Intended Use of USP <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests

In the execution of its legislated responsibilities, the FDA commonly refers to standard test methods detailed in the United States Pharmacopoeia (USP). Microbiological test methods (known as general chapters) are listed in chapters 51-80 with details regarded as enforceable where referenced as a test method. USP <61> ′Microbiological examination of nonsterile products: microbial enumeration tests′ is a globally harmonized chapter, that has been successfully employed, for the enumeration of microorganisms recoverable from non-sterile finished drug products. The content of USP <61> is not always scientifically principled nor emphatically understood by all pharmaceutical microbiologists. Consequently, misunderstanding and misapplication of USP <61> may result in analyses and assessments of microbiological quality that is flawed or erroneous. In this article, -clarification is provided to assist the pharmaceutical microbiologist in the appropriate and intended use of USP <61>, including provision of details not always commonly known or understood.