Airborne human-associated ARGs in municipal wastewater treatment plants

Antibiotic resistance genes (ARGs) in bioaerosols pose significant health hazards to humans because of their inhalability. Municipal wastewater treatment plants (MWTPs) are one of the typical sources of bioaerosol generation. However, there is a lack of clear understanding of human-associated ARGs (HA-ARGs) in bioaerosols from MWTPs. This study focused on airborne HA-ARGs in a typical MWTP. The results found that 331 HA-ARGs were identified in bioaerosols, dominated by multidrug, aminoglycoside, β-lactam, macrolide, lincosamide, and streptogramin genes. The detected abundances of the airborne HA-ARGs were 5.77-2.12E+ 03 transcripts per kilobase million (TPM), 202.36-3.17E+ 09 copies/ngDNA, and 4.42-4.92E+ 06 copies/m³_air. The greatest abundances were detected mainly in the sludge dewatering house and in the summer and winter. HA-ARGs were mainly propagated and amplified by vertical gene transfer (VGT) and horizontal gene transfer (HGT). Proteobacteria, Actinobacteria, and Bacteroidetes were bacteria that had a strong co-occurrence with airborne HA-ARGs in VGT. Plasmids and transposases were the dominant mobile genetic elements in HGT. The analysis of co-occurrence network showed that VGT was identified as the main pathway for the spread and amplification of airborne HA-ARGs, with an average contribution of 85.38 %. These results provide a theoretical basis for potential risk assessment and reduction of airborne HA-ARGs in MWTPs.