ASTM E1766-95(2002)

The test method is designed to demonstrate that all accessible surfaces and internal recesses or lumina of previously cleaned, reusable medical devices can be rendered free of recoverable microorganisms when processed in a specified sterilizer cycle.

Surviving spores are recovered by swabbing, brushing, or irrigating with an elution fluid. Recovery methods may be enhanced by mechanical action, sonication, and repeated flushing with elution fluid.

Note 1—The spore inoculation technique described in this test method is only one of the available procedures for testing the sterilization of devices. Spores on paper strips (biological indocators) are a traditional tool used to develop and monitor sterilization cycles and are also appropriate for the evaluation of sterilization of medical devices.⁶

1.1 This test method covers a reproducible procedure for testing processes used to sterilize reusable medical devices (instruments). This test method is not designed to validate a sterilization process, but tests an established sterilization cycle or process. It is a practical test of the effectiveness of a sterilization process applied to reusable medical devices. Bacterial spores more resistant to the test sterilant than the natural bioburden of the instrument are used as the test organisms. Commercially available liquid suspensions of bacterial spores are used to inoculate the instruments.

1.2 This test method is intended for reusable medical devices cleaned in accordance with the device manufacturer's instructions and prepared for sterilization in accordance with the instructions for the sterilization process being used.

1.3 This test method assumes that cleaned, reusable medical devices will be free of visible soil but may have remaining adherent bioburden. A worst-case bioburden can be represented by suspensions of bacterial endospores, which are commercially available for monitoring chemical or physical sterilization processes. These endospores should have a verifiable resistance (D value) to the specific process and sterilant being evaluated.

1.4 It is impractical to test for the sterility of some devices by immersion in growth medium because of their complexity, size, and availability (for long-term incubation) or adverse effects on the devices from long-term immersion. Therefore, elution, rinsing, or swabbing techniques are used to recover test organisms from inoculated devices.

1.5 A recovery control will be included by inoculation of a test device and use of the elution methods without applying the sterilization process being tested. A minimal recovery of 10⁶ colony-forming unit (CFU)/mL per device is required for the recovery control.

1.6 Results of the recovery control and process test cycle are compared to determine the effectiveness of the sterilization process.

1.7 Results of the recovery control and applied inoculum are compared to determine the recovery efficiency, if desired.

1.8 The procedure should reveal that tested devices are free of recoverable microorganisms when five or more consecutive tests are conducted.

1.9 A knowledge of microbiological techniques is required to conduct these procedures.

1.10 The values stated in SI units are to be regarded as the standard.

1.11 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.