Influence of Pig Farming on the Human Gut Microbiota: Key Role of Airborne Microbial Communities

It has been hypothesized that genetics and diet influence the composition of the human caecal microbiota. However, it remains unclear if and how occupational microbial exposure impacts the microbial communities of the human gut. Using a one health approach, pig farms (n=26) were visited and stool specimens of pig farmers (n=59), air samples (n=19) and rectal swabs of pigs at three different growth stages (n=144) collected. Samples from a group of cow farmers were included as control group (n=22). The microbiota of all samples was characterized by 16S rDNA sequencing and the DADA2 pipeline.In contrast to cow farmers, we found that the microbial composition of stool samples from pig farmers shared extensive fractions with samples from the pigs. Specifically, increased Prevotellaceae and decreased Bacteroidaceae were observed for pigs (and pig farmers?) as compared to cow farmers. Using DADA2, relevant sequence variants (SVs) were co-identified in pigs, air and stool samples from pig but not cow farmers. Dissimilarity indices were significantly increased for the pigs within as compared to between pig farms for all three growth stages (suckling, weaning and fattening pigs). We hypothesize that SVs originating from pig feces circulate in the stable air and by breathing get trapped in the mucus of pig farmers. Through ingestion and hence, transfer into the gastrointestinal tract the composition of the farm workers' gut microbiota is subsequently altered. The consequence of this finding on human health and the epidemiological impact regarding transfer of resistance genes needs to be further investigated.