We offer USP <61> Microbial Enumeration Testing to support pharmaceutical, nutraceuticals, and cosmetic development, quality control, and release testing of non-sterile drug substances, products, and raw materials. Our laboratory performs compendial microbial enumeration testing to determine the total aerobic microbial count (TAMC) and total yeast and mold count (TYMC) in accordance with USP requirements.
Method Suitability and Neutralization Assessment
Prior to routine microbial enumeration, a USP 61 method suitability (neutralization) study is performed to evaluate whether the test article exhibits antimicrobial activity that may interfere with microbial recovery. During this phase, we assess recovery of representative microorganisms in the presence of the product matrix.
The suitability study is performed using the following compendial test organisms:
- Staphylococcus aureus
- Pseudomonas aeruginosa
- Bacillus subtilis (or Bacillus spizizenii, as applicable)
- Candida albicans
- Aspergillus brasiliensis
These organisms represent a broad range of Gram-positive and Gram-negative bacteria, yeast, and mold, and are used to confirm that the test system can reliably recover microorganisms in the presence of the product.
If inhibition is observed, we identify and apply an appropriate neutralizing agent or validated neutralization approach to eliminate antimicrobial effects while preserving organism viability.
Once suitability is confirmed and recovery criteria are met, the method is considered valid for accurate microbial enumeration.
Total Microbial Enumeration (TAMC / TYMC)
Following successful suitability confirmation and neutralization if necessary, samples are tested for total aerobic microbial count (TAMC) and total yeast and mold count (TYMC) using compendial methods appropriate for the product type, including membrane filtration, pour plate method or surface spread methods.
This testing provides quantitative assessment of microbial bioburden and is widely used for batch release, stability studies, and routine quality control of non-sterile pharmaceutical products.