Microbiological testing - Glossary

Microbiological testing is an umbrella term for regulated biological assays that check for viable microbes and endotoxins. In peptide lab reports, these tests matter because chemical purity alone does not prove biological safety or suitability for injection and cell culture. Even a high-purity peptide can be unsafe if it contains biological contaminants.

When you review a Certificate of Analysis (COA), microbiological testing shows whether a peptide was checked beyond its chemical identity. A peptide can be 99% chemically pure and still harbor dangerous bacteria or endotoxins. If a COA lacks a sterility or endotoxin pass result, the product is for research use only and has not been verified as safe for injection.

Primary types of microbiological testing for peptides

Bioburden is the quantitative count of total viable microbes present before the sterilization process.
Sterility testing verifies that no living microbes are present in the finished product.
Endotoxin testing detects fever-inducing fragments of dead bacteria, typically using horseshoe crab blood.

Common misconceptions in microbiological testing results

Bioburden and sterility are often confused, but they answer different questions. Bioburden is a quantitative count of microbes before sterilization. Sterility is a qualitative assurance of zero growth afterward.

Sterile does not mean endotoxin-free. A product can be sterile and still contain dangerous endotoxins, because these non-living fragments often survive standard sterilization and require separate testing.

Chemical tests such as HPLC identify the specific molecule. Microbiological tests check what else may be in the vial to ensure biological safety.

Primary types of microbiological testing for peptides

Common misconceptions in microbiological testing results

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