Sterility tests are done on formulated sterile fill, or terminally sterilized end-products. Two separate sterility tests are done according to current Good Manufacturing Practices (cGMP) as defined by the FDA and USP <71> Sterility Tests by either direct inoculation or membrane filtration and a 14-day incubation period in two types of test media: (1) fluid soybean casein (fSC) broth; and (2) fluid thioglycollate (fTG) broth for anaerobic and aerobic growth.
Sterility is defined as being free from bacteria or other microorganisms, and a specimen would be deemed sterile only when there is complete absence of viable microorganisms from it. However, absolute sterility cannot be demonstrated without the complete destruction of every unit in a lot, so representative numbers of tests are done for each lot depending on lot size as per USP<71>. For very small lots aseptically filled with a defined a Beyond-Use-Date (BUD) based on sterility risk and properties of the product, as per USP <797> Pharmaceutical Compounding-Sterile Preparations and USP <1211> Sterilization and Sterility Assurance of Compendial Articles guidances. Additional testing may be done to quantify colony-forming units (CFUs) and to determine the Genus and species of the organisms. Minimum test time is 14 days plus time for reporting.