ASTM E3251-20

4.1 Single-use systems (SUSs) used for biopharmaceutical manufacturing must maintain sterility and product quality of the fluid inside. Such articles or systems should therefore be validated as providing an effective barrier against microbial ingress. The microbial barrier properties of a SUS may be demonstrated using deterministic physical tests that have been correlated to microbial integrity. Two test methods (aerosol exposure and immersion exposure) are described that can be used to demonstrate microbial integrity of a SUS or determine the MALL, the maximum defect size that does not allow microbial ingress, into a SUS.

4.2 It is important to note that the results of microbial ingress tests are heavily dependent on the conditions under which the test is performed and are not suitable for routine checking of a SUS due to the test’s destructive nature.

4.3 The selection of challenge microorganism and minimum target challenge concentration should be based on a risk assessment, justified, and validated, as necessary, for the limit of detection. A minimum of 10⁶ CFU/cm² surface area (aerosol) or 10⁶ CFU/mL (liquid immersion) is typically used (ISO 15747 and Aliaskarisohi4.4 SUS test articles bearing calibrated defects may be produced and tested to allow either the determination of the minimum defect size that can be detected by a microbial test method under given conditions (for example, microbial ingress) or to determine the MALL of SUSs under use-case conditions (for example, aerosol test).

4.5 These procedures should be conducted in a microbiological laboratory by trained personnel. It is assumed that basic microbiological equipment and supplies for conducting routine microbiological manipulations (for example, standard plate counts, autoclave sterilization, etc.) are available.

1.1 The microbial test method outlined in this document applies to microbial ingress risk assessment of a single-use system (SUS) or its individual components that require integrity testing either by the assembly supplier or the end user of the assembly based on a potential risk of a breach to the product or manufacturing process.

1.2 The aim of microbial ingress testing of sterile SUSs used in biopharmaceutical manufacturing is two-fold:

1.3 Both purposes for microbial ingress testing as described in 1.2.1 and 1.2.2 can either be conducted by liquid immersion or aerosol exposure. For the purpose described in 1.2.2, the type of exposure should be determined according to the SUS’s use-case conditions and a risk assessment.

1.4 The method used to create a breach, hole or defect in single-use film or in a SUS test article, as well as the analytical method used to physically characterize the defect size is outside of the scope of this document. The sampling plan for a given test article should be justified with the rationale of sampling size to obtain a statistically meaningful effect (Practice E3244). Determining the appropriate number of SUS test articles will depend on a risk assessment of the SUS and the conditions of its use and is also outside of this document’s scope.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.