Sterility testing represents a critical step within the overall contamination control strategy (CCS) for sterile products. Unlike environmental monitoring, in-process controls, or other types of testing, sterility testing is performed at the end of the manufacturing process and relies on a limited sample size. As a result, the conditions under which sterility testing is performed carry a heavy weight during audits and investigations. In this Pharma Matters Q&A, Amina Rahmoune, Laboratory Operations Manager, Sterility Assurance, Nelson Labs, explains how sterility testing in cleanrooms and isolators must be evaluated in the context of how effectively these environments support contamination control, not simply whether they meet minimum environmental classifications.

To support a comprehensive CCS, Rahmoune tells Contract Pharma, sterility testing environments are expected to align with manufacturing controls, personnel practices, and monitoring programs. European Union (EU) Good Manufacturing Practice (GMP) Annex 1 (2022) states that contamination control should be holistic, lifecycle-based, and documented, and should extend beyond manufacturing and take into consideration quality control activities, such as sterility testing. Sterility testing in traditional cleanrooms relies on aseptic techniques by operators, gowning practices, cleaning and disinfection, and environmental monitoring to maintain control. While this approach remains highly suitable when properly designed and managed, it introduces variability that must be actively mitigated through training, trending, and proceduralized practices (Parenteral Drug Association Technical Report No. 1). In contrast, sterility testing in an isolator reduces reliance on human factors by creating a physical separation between personnel and the test environment, which aligns closely with EU GMP Annex 1’s emphasis on eliminating contamination risks at the source rather than managing them procedurally.

According to Rahmoune, sterility testing environments must ensure aseptic handling in accordance with United States Pharmacopeia (USP) , “Sterility Tests.” Multiple CCSs can be implemented when it comes to providing an aseptic environment for sterility testing. While both isolators and cleanrooms are…