Inhalable bioaerosols, bacterial microbiome, and inflammation: A day in the life of a dairy worker

摘要

Dairy workers are at the nexus of bioaerosol exposures, which contain microbial communities and associated pro-inflammatory components. These workers experience adverse respiratory health outcomes. We evaluated the full size distribution (from 0 to 100 μm in aerodynamic diameter) and biological composition of dairy milking parlor bioaerosols across four aerodynamic size fractions (<3, 3- 10, 10-30, and >30μm). Our focus was on modeling microbial communities using high-throughput DNA sequencing. In a related study, we conducted a panel study measuring cytokines in sequential nasal lavages from dairy workers over repeated workdays to model the inflammatory response from bioaerosol exposure. Cytokines were measured using Luminex, a multiplexing assay. We used linear mixed models to understand the association between inhalable dust and select constituents (endotoxin and (3-glucans) and transcripts coding for pro-inflammatory (TNF-α) and anti-inflammatory (IL-10) cytokines. Airborne particulate mass followed a bimodal size distribution (one mode at 3 pm and a second above 30 pm), which also correlated with the relative concentrations of the following microbiological markers: bacterial endotoxin, 3-hydroxy fatty acids, and muramic acid. DNA sequencing of these aerosols revealed a diverse microbiome containing potentially hazardous constituents and opportunistic pathogens. Findings from our repeated measures affirm that workplace endotoxin exposures play a meaningful role in subclinical inflammation. A total of 36 workers (7 female, 29 male) participated for a median of 3 days (range: 1 - 3). Controlling for gender, smoking status, and length of employment, we found that a 10 EU increase in endotoxin was associated with a 0.12 pg/mL increase in TNF-α (95% CI: 0.0007, 0.244) and a 0.073 pg/mL decrease in IL-10 (95% CI: -0.142, -0.004). These studies are the first of their kind and are helping to inform a current intervention study to develop effective control strategies.