2025 Volume 56 Issue 1 Pages 38-45
Sterile pharmaceutical products are required to be free from microbial contamination as determined using the Sterility Test in the Japanese Pharmacopoeia. In this test, the products are cultured in fluid thioglycollate medium (FTM) and soyabean casein digest medium (SCDM) for at least 14 days to detect microbial growth. Previously, we examined the suitability of FTM and SCDM to detect five micro-organism species (Bacillus subtilis, Candida albicans, Clostridium sporogenes, Pseudomonas aeruginosa, and Staphylococcus aureus) described in the Sterility Test and three bacterial species (Methylobacterium extorquens, Mycobacterium chelonae, and Serratia marcescens subsp. marcescens) that have been identified in recalled pharmaceuticals. However, not all micro-organisms inoculated at the level of 10 colony forming units (CFU) were detected in FTM and SCDM, and incubation for 28 days was necessary to detect M. extorquens in SCDM. Further, the detectability of other bacteria identified in recalled pharmaceuticals, such as Burkholderia cepacia, Pseudomonas fluorescens, Ralstonia pickettii, has not been verified yet. Therefore, this study aims to investigate the suitability of FTM and SCDM for detecting B. cepacia, P. fluorescens, R. pickettii, and M. extorquens inoculated at the levels of 10 and 100 CFU. After inoculation of 100 CFU, all bacteria were detected in both media, except for M. extorquens in FTM. After inoculation of 10 CFU, B. cepacia, M. extorquens, P. fluorescens, and R. pickettii were all detected in SCDM. However, M. extorquens in SCDM required at least 28 days for detection. Furthermore, although B. cepacia and P. fluorescens were detected in FTM, R. pickettii and M. extorquens were not completely detected at the 10 CFU level. These results suggest that different culture media or alternative detection methods are needed to ensure reliable detection of M. extorquens.
