Pig finishing buildings and broiler chicken barns contribution to outdoor airborne microbiota and antibiotic-resistance genes: From the source to the farms surroundings

Mechanically ventilated livestock operations continuously emit bioaerosols containing bacteria and antimicrobial resistance genes (ARGs), yet their environmental dispersion remains poorly characterized. This study assessed the characterization of airborne microbial and ARG markers from two pig finishing buildings (PFBs) and two broiler chicken barns (BCBs) across a one-kilometer distance gradient. Air samples were analyzed for microbial and ARG concentrations and bacterial diversity. A one-phase exponential decay model revealed a rapid decline in airborne concentrations within the first 10 meters from the source, with half-distances generally below 10 meters. Despite differences in animal species and husbandry conditions, reduction rates were similar across farm types, suggesting consistent physical dispersion processes. Microbial diversity indices did not vary significantly with distance, but the relative abundance of bacterial genera showed shifts in community structures along the distance gradient. Bacteria profiles around farms were different from those compared to control sites. Network analyses revealed denser ARG-bacteria associations in PFBs, particularly involving tetracyclines and macrolides resistances, compared to BCBs. These findings suggest that emitted bioaerosols can persist beyond immediate farm boundaries and contribute to background environmental levels. This study highlights the importance of including air in surveillance programs and supports the need for integrated One Health approaches to better understand and mitigate the environmental spread of pathogens and antimicrobial resistance.