# Associations Between Fine Particulate Matter-Associated Bacteria and Respiratory Tract Microbiota in Pigs

## TL;DR

This study explores how bacteria in fine particulate matter (PM2.5) in pig farms relate to the respiratory microbiota of pigs, highlighting the role of PM2.5 as a potential carrier of pathogens.

## Contribution

The study identifies PM2.5 as a vector for potential respiratory pathogens in pigs and reveals distinct microbial community patterns in PM2.5 and respiratory tracts.

## Key findings

- PM2.5-associated bacteria vary with sampling height and are more similar to upper respiratory tract microbiota.
- 140 core potential bacterial pathogens were identified in both PM2.5 and pig respiratory tracts.
- PM2.5 and respiratory tract microbial communities show distinct interaction and assembly patterns.

## Abstract

Air quality and biosecurity in pig farms are increasingly recognized as essential for preventing disease outbreaks, protecting animal welfare, and maintaining the economic viability of the pork industry. This study collected fine particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) at different heights within pig farms and analyzed bacterial community distribution using high-throughput sequencing technology. The results revealed distinct variations in the overall bacterial community and the distribution of pathogenic bacteria at different heights. As an important carrier of bacteria and pathogens, PM2.5 warrants effective management to safeguard piggery health and mitigate losses associated with respiratory diseases, thereby contributing to a more sustainable pig production system.

Environmental health and biosecurity in pig farms and surroundings are increasingly threatened by pathogenic bacteria carried by fine particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) in enclosed piggeries. However, limited attention has been given to these pathogens and their association with the respiratory microbiome of pigs. Using high-throughput sequencing, we investigated the overall and pathogenic bacterial communities attached to PM2.5 in pig houses, as well as those in the upper (URT) and lower respiratory tracts (LRT) of healthy fattening pigs. Concentrations of PM2.5, particulate matter with an aerodynamic diameter of 10 μm or less (PM10), ammonia (NH3), total volatile organic compounds (TVOCs), and hydrogen sulfide (H2S) were significantly higher inside the piggery than in the surrounding environment. The composition of PM2.5-associated bacteria varied with sampling height and showed greater similarity to the microbiota of the URT, particularly the oropharynx, than to that of the LRT. Additionally, 140 core potential bacterial pathogens were identified via Venn analysis in both PM2.5 and respiratory tracts. Co-occurrence network analysis and community assembly patterns revealed that microbial communities in PM2.5 and the respiratory tract exhibit distinct interaction and assembly characteristics. These findings highlight the potential role of PM2.5 as a vector for respiratory pathogens and underscore the importance of air quality management in pig farming to safeguard environmental health.