The Sterility Test specified in USP General Chapter <71> is understood to mean that pathogenic bacteria, yeast and/or fungi are absent from the article labeled “sterile”. In the United States, Europe, Japan, Australia and Canada the word “sterile” has that legal meaning. We don’t often think that we live in an environment surrounded by millions and billions of invisible microorganisms. The vast majority of them do not make us sick and in fact we could not live on earth today without them. However, pathogens like E.coli or Pseudomonas or Salmonella or Mycoplasma can and do make us sick, especially if we are older, infirmed or immunocompromised. Recently the methodology used to determine if an article labeled sterile is sterile (sterility testing) was harmonized amongst the United States, European and Japanese Pharmacopoeias. In our blog about USP Monographs, we mentioned that a USP monograph defines specific quality attributes. USP monographs which contain the “sterile” attribute must meet the requirements of sterility as defined in Chapter 71. For example, Sterile Water for Injection is prepared from Water for Injection that is sterilized and suitably packaged. It contains no antimicrobial agent or other added substance. Thus, sterility Testing is the official referee test to determine legally if an article is sterile or not. An article labeled sterile is manufactured by a process that itself is validated to be effective with a very high degree of probability. This concept is known as the sterilization assurance level [SAL]. The current state of the art is a SAL of one in one million meaning that not more than one article of one million is likely to be non-sterile if a successfully validated process was followed.
Gibraltar Laboratories conducts the membrane filtration test using the Millipore Steritest system and the direct inoculation method in an ISO Class 5 sterility suite. In both methods the samples are placed in Soybean Casein Digest Medium (SCDM) and Fluid Thioglycollate Medium (FTM) and incubated for 14 days. The samples are observed for evidence of microbial contamination daily. Gibraltar Laboratories also is expert in special sterility applications such as defined in ST 79 involving challenge with relatively resistant spores to steam sterilization. Gibraltar is expert in defining the protocol to validate the steam sterilization process including Installation Qualification, Operational Qualification and Performance Qualification.