Sterility testing - Glossary - peptidetesting.cc

Sterility testing is a microbiological safety test used to identify living microbes in a finished product. The result is binary: a sample passes if no viable microorganisms are detected and fails if microbial growth occurs. For injectable substances, this is a core safety check.

Sterility testing follows USP <71> incubation and control checks

Under standards such as USP <71>, sterility testing incubates a product sample in nutrient-rich liquid media for at least 14 days. If the liquid becomes cloudy, it signals microbial growth and the sample fails. To reduce false-negative results, laboratories perform growth-inhibition checks first, confirming that the product itself does not stop microbes from growing during the test.

A passing result means no live microbes were found in the specific sample analyzed. Because the test is destructive and covers only a small subset of a batch, it gives a statistical probability of sterility, not an absolute guarantee for every unit in the production run.

Common misunderstandings about sterility testing results

Sterility testing is not an endotoxin test: It detects living organisms, while endotoxin tests look for toxic fragments from dead bacteria. A product can pass sterility testing and still contain dangerous endotoxins.
Sterility testing is not bioburden testing: Bioburden testing measures microbial count before sterilization; sterility testing checks the finished product for absence of viable microbes.
Sterility testing does not measure chemical purity: It does not evaluate amino acid sequences, heavy metals, or chemical composition. These require separate analyses such as HPLC or Mass Spectrometry.

Sterility testing follows USP <71> incubation and control checks

Common misunderstandings about sterility testing results

Sources