Validation of an automated blood culture system for sterility testing of cell therapy products

Background aims. Automated blood culture systems are widely used for the detection of microorganisms in cell therapy products. However, they are not validated by the manufacturers for this purpose. The aim of this study was to assess the ability of the Bactec system (Becton-Dickinson, Le Pont-De-Claix, France) to detect the microorganisms that could contaminate cell therapy products. Methods. Three types of vials and conditions were tested: Plus Aerobic/F and Anaerobic/F media incubated at 35 degrees C and Mycosis IC/F medium incubated at 30 degrees C. All vials were incubated 10 days. We tested 18 microorganisms, including slow growers and some with fastidious nutritional requirements (10 bacteria, four yeasts, four filamentous fungi), each with four inocula (10-104 colony-forming units) performed in quintuplicate. Results. The combination of Plus Aerobic/F and Plus Anaerobic/F vials detected all the tested pathogenic bacteria, all the tested Gram-positive skin commensal or environmental bacteria, all the tested yeasts, and three of four tested filamentous fungi. The addition of the Mycosis IC/F vial extended the range of detected microorganisms to one fungal environmental contaminant. Two bacterial environmental contaminants were not detected by our method. Low inocula of the skin contaminant Propionibacterium acnes were detected only after 7 days of incubation. Conclusions. These data suggest that (i) the prolongation of the incubation time of Plus Aerobic/F and Plus Anaerobic/F. vials from 7 to 10 days and (ii) the use of Mycosis ICfF medium make minor contributions in the sterility testing of cell therapy products. We have validated the Bactec method using aerobic and anaerobic vials incubated 7 days at 35 degrees C.