Microbial Control: Detection of Cutibacterium acnes, a high-risk aerotolerant anaerobe recovered in the biopharmaceutical industry

A microbial control program that broadens its scope to evaluate the risks associated with both anaerobic and aerobic micro-organisms will result in improved product quality and patient safety. Although the development and implementation of an anaerobic bioburden assay is process and facility dependent, the importance of testing for anaerobic bioburden is shown in the various case studies provided by multiple companies. The case studies in this paper show that, in some instances, contamination went undetected due to not having the correct test conditions in place. It is recommended that companies implement methods for detecting facultative anaerobic bacteria for upstream mammalian cell culture processes.

This peer-reviewed paper outlines the risk of aerotolerant anaerobic bacterial contamination during the manufacture of biologic drug substance (DS) and the challenges of detecting facultative anaerobes. Aerotolerant anaerobes can withstand oxygen without consuming it, making them difficult to detect. An aerotolerant anaerobic contamination can pose a risk to product quality and patient safety, and often occurs during upstream manufacturing. Upstream DS manufacturing involves using growth medium, which is prepared in an open environment, manually, with materials that have a high nutrient content. Upstream DS manufacturing also occurs at warm temperatures, and has long process durations without filtration, providing Cutibacterium acnes (C. acnes) with an environment to successfully proliferate. The upstream process presents a high risk for C. acnes contamination. Because of this, the most likely point of detection is at the end of the production of upstream processing.

The case studies from multiple biopharmaceutical companies outlined here include instances where contamination events occurred during upstream processing and it was not possible to detect them by using routine bioburden testing methods. Most of these contaminations were detected by process monitoring, which is slow to detect anaerobic contamination. After experiencing these anaerobic contamination events, companies decided to implement anaerobic bioburden testing. Since traditional aerobic bioburden tests may not detect aerotolerant anaerobes, several different methods have been implemented to detect C. acnes.

In conclusion, a microbial control program that broadens its scope to evaluate the risks associated with both anaerobic and aerobic micro-organisms will result in improved product quality and patient safety. The importance of testing for anaerobic bioburden is shown above in the various case studies provided by biopharmaceutical companies. The case studies show that, in some instances, contamination went undetected due to not having the correct test conditions in place. Because of this, it is recommended that companies implement methods for detection of aerotolerant anaerobic bacteria for upstream mammalian cell culture processes.