- Sterility testing is a critical quality attribute for advanced therapy medicinal products (ATMPs), including bone marrow–derived mesenchymal stem cells (BM-MSCs).
- Compendial sterility methods mandated by pharmacopeial standards (e.g., USP <71> and Ph. Eur. 2.6.1) require up to 14 days, often exceeding the practical shelf life of cell-based products.
- A validated 2-day sterility test enables timely clinical release without compromising microbiological safety, representing a major advance for time-sensitive regenerative therapies.
Key Findings
Lysák et al. evaluated an automated blood culture system (BACTEC, Becton Dickinson) against the European Pharmacopoeia 14-day sterility test using supernatant from bone marrow–derived MSC cultures produced under GMP conditions in an academic cleanroom facility. Samples were collected 48 h prior to cell harvest and inoculated with three bacterial and three fungal species at target concentrations ranging from ~1 to 1,000 CFU to assess time to detection (TTD) and sensitivity.1
- Rapid bacterial detection: Staphylococcus aureus and Pseudomonas aeruginosa were detected in <18 h at ~1–10 CFU using the automated system, compared with ~24 h using the compendial method.
- Improved detection of slower-growing bacteria: Bacillus subtilis at ~10–100 CFU was detected significantly faster by the automated system (mean TTD ~10.3 h) than by the compendial method (~60 h).
- Accelerated fungal detection: Candida albicans and Aspergillus brasiliensis at ~10–100 CFU were detected earlier using automated culture (15.5 h and 31.5 h, respectively) than with the compendial method (48 h).
- Comprehensive detection within 48 hours: All tested organisms were detected within 48 hours using the automated system at sensitivity levels of ~1–10 CFU. In contrast, B. subtilis required up to 72 hours for detection using the compendial method.
- Release-compatible timeframe: The 2-day automated sterility test provided microbiological assurance equivalent to the compendial method, within a timeframe compatible with clinical MSC product release.
Bigger Picture
This study demonstrates that automated blood culture systems can be successfully adapted for rapid sterility testing of cell-based therapeutic products. Confirming sterility within 48 h addresses a major bottleneck in ATMP manufacturing, particularly for products with limited stability or urgent clinical need. When supported by appropriate validation, such rapid methods align with emerging regulatory acceptance of alternative sterility testing strategies and contribute to faster, safer delivery of advanced cell therapies.
(Image credit: iStock / James Mutter)
References:
- Lysák et al. 2016. Validation of Shortened 2-Day Sterility Testing of Mesenchymal Stem Cell-Based Therapeutic Preparation on an Automated Culture System. Cell and Tissue Banking.
