Thank you for your question. In performing direct inoculation testing as you described, since there is a transfer step between the sample and the media jar, where the syringe / needle is outside of either container, it wouldn’t be considered a “closed system”. However, with proper aseptic technique and environmental controls in place, this process can be performed in an aseptic manner. Regarding volumes of sample per filter, there is no defined maximum sample volume which can be passed through a filter, assuming no clogging / filterability issues are observed. However, USP does state for testing of aqueous solutions to not exceed rinsing with “5 times 100 mL per filter, even if during method suitability, it has been demonstrated that such a cycle does not fully eliminate the antimicrobial activity.” As you mentioned, proper validation (method suitability) is required to demonstrate the chosen method is effective for the formulation and sample volume being tested. Please contact us if you have additional questions: info@arlok.com.

@@ARLBioPharma thanks for getting back to me. I'll drop you an email as I have some more questions.

@@ARLBioPharma confusion re the closed system aspect as with filtration one must still use a needle from a sterility test kit? 🙄