Particle-size stratification of airborne antibiotic resistant genes, mobile genetic elements, and bacterial pathogens within layer and broiler farms in Beijing, China.

The particle-size distribution of antimicrobial resistant (AMR) elements is crucial in evaluating their environmental behavior and health risks, and exposure to the fecal microbiome via particle mass (PM) is an important route of transmission of AMR from livestock to humans. However, few studies have explored the association between air and fecal AMR in farm environments from the perspective of particle-size stratification. We collected feces and PMs of different sizes from layer and broiler farms, quantified antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and human pathogenic bacteria (HPB) using Droplet digital PCR (ddPCR), and analyzed the bacterial communities based on 16S rRNA sequencing. The particle-size distributions of 16S rRNA and AMR elements were similar and generally increased with larger particle sizes in chicken farms. In broiler farms, we observed a bimodal distribution with two peaks at 5.8-9.0 µm and 3.3-4.7 µm. The dominant airborne bacterial phyla were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. The dominant phyla in the feces were the same as those in the air, but the order of relative abundance varied. The particle-size distributions of specific bacterial genera differed between the animal-farm types. Overall, the degree of association between feces and different particulates increased with increasing particle size. The microbial communities in the coarse particles were similar to those in fecal samples. Escherichia coli, Staphylococcus spp., Campylobacter spp., and sul 2 (sulfonamide ARGs) tended to attach to small particles. We highlight the particle size-specific relationship between fecal and air microbes involving ARGs, MGEs, and HPB and provide valuable information for comprehensively assessing the transmission of fecal microorganisms through the airpath and its environmental and occupational health risks.

Airborne fungi and human exposure in different areas of composting facilities.

Airborne fungi can pose serious health concerns in humans; however, the area-specific abundance and composition of airborne fungal microbiota discharged from composting facilities remain unclear. In the present study, we collected air samples from composting, packaging, office, and downwind areas of four commercial composting facilities. The characteristics of airborne fungi, including pathogen/allergen-containing genera, and their corresponding human exposure in different areas of composting facilities were analyzed using high-throughput sequencing and ddPCR. High fungal concentrations and richness were detected in the air of the packaging area. In all four areas, Ascomycota, Basidiomycota, and Mucoromycota were observed to be the primary fungal phyla, with Cladosporium, Alternaria, and Aspergillus as the consistently dominant fungal genera. A large number of endemic airborne fungi were found in the composting and packaging areas, which also shared the most common airborne fungi as well as pathogen/allergen-containing genera. The packaging area contributed substantially to airborne fungi in the office and downwind areas. Area-specific human exposure to broad airborne fungal compositions was revealed, especially regarding the pathogen/allergen-containing genera. Current results provide valuable data for a comprehensive understanding of area-specific airborne fungi in composting facilities and highlight the importance of assessing the inhaled exposure to airborne fungi in evaluating their following health risks.

Aerosolization Behaviour of Fungi and Its Potential Health Effects during the Composting of Animal Manure.

Compost is an important source of airborne fungi that can adversely affect occupational health. However, the aerosol behavior of fungi and their underlying factors in composting facilities are poorly understood. We collected samples from compost piles and the surrounding air during the composting of animal manure and analyzed the aerosolization behavior of fungi and its potential health effects based on the fungal composition and abundance in two media using high-throughput sequencing and ddPCR. There were differences in fungal diversity and richness between the air and composting piles. Ascomycota and Basidiomycota were the two primary fungal phyla in both media. The dominant fungal genera in composting piles were Aspergillus, Thermomyces, and Alternaria, while the dominant airborne fungal genes were Alternaria, Cladosporium, and Sporobolomyces. Although the communities of total fungal genera and pathogenic/allergenic genera were different in the two media, fungal abundance in composting piles was significantly correlated with abundance in air. According to the analysis on fungal composition, a total of 69.10% of the fungal genera and 91.30% of pathogenic/allergenic genera might escape from composting pile into the air. A total of 77 (26.64%) of the fungal genera and six (20%) of pathogenic/allergenic genera were likely to aerosolize. The influence of physicochemical parameters and heavy metals on the aerosol behavior of fungal genera, including pathogenic/allergenic genera, varied among the fungal genera. These results increase our understanding of fungal escape during composting and highlight the importance of aerosolization behavior for predicting the airborne fungal composition and corresponding human health risks in compost facilities.

[Diversity and Community Structure of Airborne Fungi in Different Working Areas of Composting Plants].

Composting plants are an important source of airborne fungi. At present, no research has been reported on differences in the types and abundance of escaped fungi in different working areas, which makes it very difficult to comprehensively assess the ecological health risks of the air in composting plants. In light of this situation, this study collected air samples from the composting, packaging, office, and downwind areas of the composting plants and used high-throughput sequencing technology to analyze and compare the biological diversity and community structure of airborne fungi in the four areas. The source of airborne fungi in offices and downwind areas was further traced. The results showed that the highest abundance and diversity of airborne fungi were found in the packing and composting areas of the composting plants. Ascomycota and Basidiomycota were two fungal phyla with the highest relative abundance in the four regions. Overall, the distribution of dominant fungal genera differed; Trichocomaceae and Davidiella were the dominant genera in three areas of the composting plants. Among the 136 detected fungal genera, the number of endemic airborne fungal genera in the composting and packaging area was the largest, and 52.94% of the fungal genera was shared by the four areas. At the level of fungal genera, the community structures in the air in three areas of the composting plants were similar. The statistical difference analysis results of the key genera in different areas of the composting plants showed that the number of different fungal genera between the downwind, packaging, and composting areas was the largest, and no statistically different fungal genera were detected in the air between the packaging and composting areas. The Source Tracker analysis results showed that the contribution percentage of the packaging and composting areas to the airborne fungi in the office and downwind areas was between 9.52%-15.85%. The results of this study will provide basic data for evaluating the relationship between airborne fungal exposure and human health in different areas of the composting plant, as well as its ecological impact on the surrounding air environment.