USP <61> - Microbiological Examination of Nonsterile Products - Microbial Enumeration Tests

What it says

General Chapter <61> describes methodology for enumerating total aerobic microbial count and total combined yeasts and moulds count in nonsterile pharmaceutical products, including method suitability testing to confirm the product does not inhibit microbial recovery.

Paraphrased for plain-language clarity. Always verify against the current published regulation text.

What it means in practice

• Method suitability testing, confirming the specific product formulation does not itself inhibit microbial growth or recovery, is a required precondition before routine enumeration results for that product can be considered valid.
• This chapter applies specifically to nonsterile products, working alongside Chapter <62> which addresses testing for specified, potentially objectionable organisms, together forming the microbiological quality control framework for nonsterile products.
• Acceptance criteria for microbial counts are product and route-specific, connecting back to the objectionable organism risk assessment described under 21 CFR 211.113.

What inspectors look for

• Whether method suitability testing was performed and passed for the specific product formulation before routine enumeration testing began.
• Whether microbial count acceptance criteria are documented with a rationale connecting them to the product's specific route of administration and patient population.
• Whether recovery methods and neutralisation of antimicrobial preservatives, where applicable, are validated as part of method suitability.

Related regulations