Direct Inoculation and Membrane Filtration Methods

Sterility testing is required to ensure viable contaminating microorganisms are not evident in a product. This testing is conducted by direct inoculation or membrane filtration methods and can be performed in an isolator or cleanroom environment.

Sterility Testing Techniques

Direct Inoculation

  • The test article is directly inoculated into two types of media to allow for the detection of both aerobic and anaerobic microorganisms.
  • After inoculation, both media types are incubated for 14 days. Intermittent observations as well as a final observation at the end of the testing period are conducted to detect evidence of microbial contamination.

Membrane Filtration

  • Sterile, enclosed units allow for the simultaneous filtration of equal volumes of test samples through two membrane filters.
  • Samples are incubated in two types of media for 14 days, facilitating the detection of both aerobic and anaerobic microorganisms.

Bacteriostasis/Fungistasis Testing – B/F Testing

In conjunction with the sterility test, bacteriostasis fungistasis testing is performed to assess whether or not the test article is inhibitory to the growth of microorganisms. The performance of the B/F test is necessary to validate the sterility result and confirm that there are no antimicrobial properties within the test article that would inhibit the detection of microbial organisms during the sterility assay.

Vaporized Hydrogen Peroxide (VHP) Ingress Testing

Vaporized hydrogen peroxide (VHP) ingress testing is performed within an isolator that undergoes VHP decontamination. This assay evaluates if VHP ingress into a test article container is evident, which may affect the validity of the results.

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In addition to offering the convenience of performing sterility testing at our sites in Ireland and Pennsylvania, we have cutting-edge technologies to support rapid sterility testing in-house using Celsis® ATP bioluminescence instruments.

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Frequently Asked Questions (FAQs) for Sterility Testing

  • What is sterility testing?

    Sterility testing is designed to demonstrate the presence or absence of extraneous viable contaminating microorganisms in biological parenterals designed for human use.

  • Why is sterility testing performed for 14 days?

    The sterility assay is 14 days allowing for an appropriate incubation period to detect slower-growing microorganisms. While many bacterial and fungal organisms can be detected in a shorter incubation period, some microorganisms require a longer incubation period to proliferate.

  • What is Sterility Test USP <71>?

    Sterility test USP <71> reflects the chapter within the United States Pharmacopeia (USP) that outlines the manner in which a sterility assay should be performed, including details of the methodology and how a product should be tested based upon sample size and fill volume.