Bacterial diversity in the indoor air of pharmaceutical environment

To monitor bacterial diversity of ISO Class 8 pharmaceutical clean room environment using conventional culture-based methods and pyrosequencing analysis.

Bacterial isolates were obtained through viable particulate air monitoring, passive air monitoring and surface-monitoring procedures. A total of 157 bacterial isolates were obtained and assigned to four different phyla, Actinobacteria, Firmicutes, Proteobacteria and Deinococcus-Thermus, encompassing 52 species of 24 genera based on 16S rRNA gene sequence analysis. The genera Micrococcus and Staphylococcus were found as the main bacterial groups among the isolates. However, a big discrepancy was found between the culture based and pyrosequencing results. A total of 11 409 quality reads were obtained from the pyrosequencing analysis, and the subsequent phylogenetic analysis indicated that Proteobacteria was the most abundant group at phylum level, followed by Actinobacteria and Firmicutes. Bacillus, Propionibacterium and Acinetobacter were identified as the most abundant genera by the pyrosequencing analysis.

The culture-based results were in line with previous reports on the airborne bacterial composition of various environments, but the pyrosequencing analysis revealed a unique diversity of bacteria in this case. No significant pathogens above Riskgroup 2 were found from either culture based or pyrosequencing studies.

The presence of various bacterial taxa including a number of groups, whose presence in air is previously unknown, was confirmed through this analysis. The main source of bacteria in the indoor air environment of pharmaceutical processes is likely human, but no significant primary pathogens were detected. Culture-based analysis may give limited information on the bacterial diversity of air environment.