ABSTRACT Sterility testing of cellular and gene therapy products is required to ensure safe infusion for the recipient. Sterility testing is often performed using broth-based media per the biopharmaceutical compendial USP method. Automated blood culture systems have emerged as a potential alternative method, but data remain limited. It also remains unclear whether different cellular and gene therapy product formulations inhibit microbial growth during sterility testing, which could lead to false-negative sterility results. This study evaluated the ability to perform sterility testing using the BacT/Alert Virtuo automated blood culture system, BacT/Alert FA plus (aerobic) and FN plus (anaerobic) blood culture bottles, and two product formulations: (i) Plasmalyte-A + 2.5% human serum albumin (HSA) and (ii) Plasmalyte-A + 5% HSA + 5% dimethyl sulfoxide (DMSO). Contrived specimens were created using either formulation or a saline-only growth control inoculated with Staphylococcus aureus , Bacillus subtilis , Pseudomonas aeruginosa , Clostridium sporogenes , Candida albicans , or Aspergillus brasiliensis . Contrived specimens were prepared in blood culture sets consisting of an aerobic bottle and an anaerobic bottle and incubated for a maximum of 14 days. Bottles flagging positive underwent culture-dependent microbial identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for bacteria and yeast or using macroscopic and microscopic identification for filamentous fungi. The automated blood culture system method correctly flagged all contrived blood culture sets within 72 h, demonstrating no inhibitory effect on microbial recovery from either formulation. Note, both aerobic and anaerobic bottles were necessary to detect microbes with different growth preferences (e.g., strict aerobes and obligate anaerobes). Another important finding was that the addition of calcofluor staining and a Sabouraud dextrose agar (SDA) plate improved early mold detection when no organisms were detected by the initial Gram stain from a positive blood culture. Taken together, our findings suggest that two standard cellular and gene therapy product formulations do not interfere with sterility testing in an automated blood culture detection system. IMPORTANCE Cellular and gene therapy products have emerged in recent years as an important treatment modality at large academic medical centers; however, these products must be tested for microbial contamination to ensure product safety. Compared to the gold standard, agar-based solid media method, automated blood culture systems have emerged as a potential alternative method of sterility testing. Here, we evaluated the ability of an automated blood culture detection system (BacT/Alert Virtuo) to reliably detect diverse microorganisms, ranging from bacteria to mold, in two standard cellular and gene therapy product formulations. Our results support current evidence that the use of automated blood culture detection systems is a reliable alternative method of sterility testing for different formulations of cellular and gene therapy products.
Snyder et al. (Fri,) studied this question.