Microbial Testing (Microbial Limit Testing)

Microbial limit testing establishes that a herbal raw material, extract, or finished product does not harbour microbial contamination at a level presenting a risk to consumer safety, and is performed according to internationally harmonised pharmacopoeial methods. Total aerobic microbial count and total yeast and mould count are determined by plate culture methods, with permitted limits varying according to the intended route of administration — oral herbal products are typically limited to no more than 100,000 colony-forming units per gram for total aerobic count and 1,000 CFU/g for total yeast and mould count, while topical products are subject to more stringent limits reflecting their direct application to skin or mucosal surfaces. Specified pathogenic organisms, including Escherichia coli, Salmonella species, Staphylococcus aureus, and Pseudomonas aeruginosa, are tested for using selective culture media and confirmatory biochemical identification, and must be entirely absent from a defined sample weight (commonly one to ten grams) regardless of the total aerobic count result. Aflatoxin testing, addressing the potent hepatocarcinogenic mycotoxins produced by Aspergillus species that can contaminate improperly stored plant material, is performed by immunoaffinity column cleanup coupled to HPLC with fluorescence detection or by enzyme-linked immunosorbent assay screening, with strict limits applied individually to aflatoxin B1 and to total aflatoxin content.