Standard Test Method for Microbial Ingress Testing on Single-Use Systems

Importancia y uso:

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. Such physical test methods are described in Test Method E3336. Two microbial test methods (aerosol exposure and immersion exposure) are described in this test method 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.

4.2.1 Any size defect may be forced to fail under sufficiently aggressive conditions (including a large enough sample size, high differential pressure, or high hydrostatic pressure, for example) that would not ordinarily reflect normal use conditions. Thus, it is necessary to clearly define the relevant conditions for a test through a risk assessment of both the actual SUS claims and its final use (Practice E3244). Once that is established, the size of defect that can be detected under those conditions can be determined, if required, using defined defects.

4.2.2 “Relevant conditions” refers to worse-case actual use conditions but does not mean that a SUS must be tested under theoretically absolute (extreme) “worst-case” conditions.

4.2.3 Testing may be performed on individual components or entire systems. Considerations for defining “relevant conditions” and testing design should be based on a risk assessment for the SUS intended use and should include:

4.2.3.1 A channel created by a defect or breach through the film thickness or through a seam or connection which must be filled with liquid to allow microbial passage.5^, 6

4.2.3.2 Factors that could influence liquid filling of a channel, including a liquid’s viscosity, defect size and type, plastic materials and pressure applied inside the SUS.

4.2.3.3 Rationale for selecting a defect type should be based on the probable type of defect(s) that could occur during the SUS life cycle

4.2.3.4 Rationale for selection of defect sizes should be based on a deterministic physical testing method (detection limit)

4.2.3.5 Consideration of pressure(s) differential applied during testing to simulate conditions that a SUS may be subjected to during actual use conditions (Practice E3244).

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 Aliaskarisohi7).

4.4 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).

4.4.1 If the test objective is to determine the MALL and demonstrate correlation between physical integrity test sensitivity and microbial ingress, selection of the calibrated defect (laser-drilled hole, capillary, copper wire) should be based on the most probable type of defect that could occur during the SUS’s life cycle.

4.4.2 The selection of defect sizes should be based on the expected transition from ingress to no ingress under the SUS’s intended use-case conditions, alternatively, worst-case conditions can be selected. As described in the Practice E3244, a typical range is from 1 µm to 100 µm. The defect sizes should be calibrated by a defined method.

4.4.3 One approach for determining the MALL of a SUS film material is to test single-use film coupons with calibrated defects, in holders. This enables higher throughput testing; however, using coupons as test articles may not represent a scale-down model of an entire SUS.

4.4.4 Another approach is to validate the test method on alternative container-like vials. The principle remains the same. The alternative container must be able to hold the minimum size defect.

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.

Subcomité:

E55.07

Referida por:

E3244-23, E3336-22

Volúmen:

14.01

Número ICS:

07.100.10 (Medical microbiology)

Palabras clave:

aerosol; integrity; integrity test; liquid; microbial ingress test; single use system;