Sterility testing is an essential part of in-process and release testing for cellular therapy products. The FDA specifically recommends that sterility testing be performed as outlined in 21 CFR 610.12. Furthermore, because they are concerned that antibiotics may interfere with the accurate assessment of sterility testing, the FDA requires preliminary bacteriostasis and fungistasis testing according to the USP """"""""<71> Sterility Test"""""""" on all samples containing antibiotics, including cells grown in antibiotic-containing media. The methods for sterility testing described in the CFR and USP standards were developed more than 25 years ago, and are labor-intensive and require incubation for 14 days. Since the time these methods were published, more sensitive and rapid methods have been developed for detection of microbial growth in various body fluids. These modern methods include automated systems for the detection of microbial growth in blood and other normally sterile fluids. Despite the fact many laboratories use these automated systems to assess sterility of cellular therapy products, the FDA has not sanctioned this application because there are no published data from any formal comparison of these newer methods with the CFR and USP methods. For these reasons, we have developed a validation protocol comparing the CFR and USP methods with two automated culture methods: the bioMerieux BacT/Alert system and the Becton Dickinson Bactec system. Six different cell products from the Department of Transfusion Medicine (DTM) were seeded with selected bacteria (8 strains) and fungi (2 strains) (10 colony forming units and 50 CFUs) and then tested in triplicate with each method. The test sensitivity and time to detect a positive culture were assessed. With each bacterium and fungus, the automated systems were found to be more rapid and sensitive for detection of contaminated cell products. Growth of strict aerobic and anaerobic organisms grew preferentially in aerobic and anaerobic blood culture broths, respectively; therefore, each cell product would have to be cultured in the two broth formulations. A second but related study was performed for NCI to assess use of the automated culture systems for determining sterility of their cell therapy products. The design of the studies was the same as described above although a more limited number of organisms were evaluated with a single cell therapy product. The results of these studies were identical to that reported above. The data collected in these studies have been submitted to the FDA for their review. The FDA has already accepted use of the automated culture systems for processing the NCI cell products and we anticipate the same decision will be made for the DTM cell therapy products. This will result in a more sensitive and rapid sterility testing method and a significant reduction in cost for processing these products. The results of these studies have been presented at the national transfusion medicine meeting and a manuscript reporting these findings is in preparation.
| Khuu, H M; Stock, F; McGann, M et al. (2004) Comparison of automated culture systems with a CFR/USP-compliant method for sterility testing of cell-therapy products. Cytotherapy 6:183-95 |
