Application note: Microbial limits testing

In this application note, Wickham Laboratories discuss risk assessments for objectionable organisms…

Microbial Limits Testing (MLT) is used to determine whether a non-sterile pharmaceutical product complies with an established specification for microbial quality.

This is an important series of tests designed to limit the likelihood of any adverse incident occurring as a result of a high level of microorganisms being present in a non-sterile product. By setting limits on the numbers of bacteria present in the product under test you inherently reduce the likelihood of this occurring.

The harmonised test methods and specifications used to ensure the microbial quality of pharmaceuticals are described in the British Pharmacopoeia (BP), European Pharmacopoeia (Ph Eur), Japanese Pharmacopoeia (JP) and US Pharmacopoeia (USP). The Microbial Limit Testing described in these four pharmacopoeias is performed in two parts and is designed to perform the qualitative and quantitative determinations of specific viable microorganisms present in pharmaceutical products.

These parts consist of the Microbial Enumeration Test which is a quantitative enumeration of mesophilic bacteria and fungi (yeasts, moulds) that grow under aerobic conditions and the Tests for Specified Microorganisms which test for the presence of Escherichia coli, Salmonella species, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Clostridium species, and Bile-tolerant Gram-negative bacteria.