USP <71> Sterility Tests

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The United States Pharmacopeia 47 General Chapter 71, also known as USP <71>, is a method used for evaluating the sterility of a variety of products.

It has become an industry standard for sterility testing and has been continuously harmonized with the European Pharmacopeia and the Japanese Pharmacopeia to support the global pharmaceutical industry since 2002.

USP <71> consists of two tests for sterility: membrane filtration and direct inoculation of the product into culture medium. Either test may be used, but the choice depends on the product being used. All testing is conducted in an ISO 5 biological safety cabinet that is maintained in an ISO 7 cleanroom.

Membrane filtration is performed by filtering an amount of the product and transferring the membrane into culture medium. Direct inoculation is performed by separately transferring an amount of product into a container of Tryptic Soy Broth (TSB) and Fluid Thioglycollate Medium (FTM). The amount of product measured for use is dependent on characteristics of the product to be tested.

USP <71> is qualitative as each test requires visual confirmation of macroscopic microbial growth.

Summary of Test Method and Important Parameters

  • A growth promotion test is performed to evaluate the suitability of the culture media.
    • Three portions of FTM are inoculated with sporogenes, P. aeruginosa, and S. aureus separately; three portions of TSB are inoculated with A. brasiliensis, B. subtilis, and C. albicans separately.
    • The portions are evaluated for growth/turbidity.
  • A method suitability test is performed in conjunction with either membrane filtration or direct inoculation.
    • The minimum quantity of the product is transferred to either a filter unit or into culture medium. A small amount (<100 CFU) of microorganism is then added to either the rinse fluid or the culture medium.
    • This test is then carried out like the respective tests for sterility.
      • If visible growth is obtained after 5 days, then the product has no antimicrobial activity or it has been sufficiently eliminated.
      • If no visible growth is obtained, the antimicrobial activity has not been eliminated and the test conditions are modified accordingly.
    • Test for sterility – membrane filtration: The contents of the product container are transferred to the filter unit and filtered immediately. The filter is rinsed at least three times with sterile rinse fluid. The membrane is transferred into a container with culture medium.
    • Test for sterility – direct inoculation: A quantity of test product is transferred into a container with culture medium.
    • The containers are incubated for 14 days with periodic visual evaluations for macroscopic growth.
      • If no evidence of growth can be observed, then the product complies with the test for sterility.

Microchem Laboratory commits a great deal of time, effort, and care to perform the USP <71> test for sterility in accordance with the United States Pharmacopeia and the FDA. We take many measures to ensure that we maintain the sterile environment where testing is performed and are eager to answer any questions our customers may have about or otherwise related to this test.

Sources: (this is the test method itself)

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