Microbial species contributions to the inflammatory potential of occupational bioaerosol exposures from biomass-based energy production.

The production of reactive oxygen species (ROS) by neutrophils and other immune cells is essential for host defense and contributes to inflammatory responses to inhaled microorganisms. Elevated occupational exposure to bioaerosols and particles, has been shown to induce ROS production in cell-based assays. This study aimed to investigate how individual fungal and bacterial species and overall species composition contribute to ROS production induced by complex mixed bioaerosol exposures. Using a cell assay with neutrophil-like differentiated HL-60 cells, ROS production was measured after challenge with personal exposure samples from workers (n = 129) at 22 Danish biomass plants combusting straw, wood chips, wood pellets, or a combination thereof. The measured ROS production is here referred to as the total inflammatory potential (TIP) of the complex exposure samples. Associations between TIP and levels of exposures and the species of microorganisms, as identified with MALDI-TOF MS, were assessed. A mixed model including all measured exposure levels showed that TIP was associated with exposure to endotoxin, inhalable dust, and bacteria cultured aerobically at 25 °C. Analysis using constrained ordination showed that TIP was associated with the composition of bacteria cultured anaerobically at 37 °C. Finally, the species Paenibacillus barengoltzii, Pantoea agglomerans, and Aspergillus montevidensis showed positive associations with TIP, while Staphylococcus capitis was negatively associated with TIP. The results indicate that in addition to concentrations of microorganisms, microbial species may influence the capacity of mixed exposures to induce ROS production in a human cell line, and thus potentially affect the inflammatory potential of exposures.