Continuous microbiological air monitoring for aseptic filling lines

Pharmaceutical aseptic filling lines are used to fill sterile biotechnology products without affecting their quality by a terminal sterilization step. Standard grade A filling environments are required to have < 1 colony-forming unit (CFU) per cubic meter (m3) of air. Aseptic filling is the production cycle with one of the highest contamination risks. A typical method of contamination monitoring is to actively draw air and filter it through special gelatin filters.

The study aims to establish whether continuous sampling provides effective monitoring for the entire production process by determining whether trapped organisms can withstand long-term drying stress with unaltered recovery.

In two experimental phases, the study examined microbial recovery in long-term air-stressed membranes as well as the viability of microorganisms on gelatin filters during 8-hour runs of filtration with high-efficiency particulate air-filtered air from a laminar flow hood using the MD 8 Airscan system. Stressed and unstressed filters were compared with parallel-run reference filters as controls. The CFUs were counted and the genus of the identified microorganism populations determined to examine any changes in microbiological flora occurring during continuous long-term sampling.

Compared to the unstressed reference filters, neither total recovery nor recovered bacterial diversity changed. No statistically significant differences in CFUs were found between test filters and reference filters, nor were any statistically significant differences found in the microbiological flora between test filters and reference filters. CFU populations were comparable in both experiments.

Eight hours of continuous air sampling on gelatin filters with the MD 8 Airscan system did not affect total recovery or change the diversity of recovered microorganisms compared to the controls.