Distribution and migration of antibiotic resistance genes, as well as their correlation with microbial communities in swine farm and its surrounding environments

The prevalence and correlation of antibiotic resistance genes (ARGs) in pig farm wastewater treatment plants (WWTPs) and the surrounding environment were investigated using metagenomics and real time quantitative PCR. The hosts of ARGs were also studied in this study. The abundance of ARGs decreased significantly in the anoxic/oxic (A/O) process and disinfection tank of WWTPs. New ARGs emerged in wastewater that passed though the anaerobic reactor. The abundances of ARGs in the soils and waters near the WWTPs were 10- and 35-fold higher than those in the control, respectively. The abundance of ARGs in wells near the WWTPs were an order of magnitude higher than that in the control. Similarly, a high abundance of ARGs was detected in pig manure. After composting, most of the ARGs were eliminated, but sul1 increased by 10.5-fold. A high-throughput analysis revealed that the WWTPs altered the microbial community structure in the surrounding environment, with 52% and 37% of the operational taxonomic units (OTUs) endemic to the soil and water samples near WWTPs in comparison with these data in the control, respectively. The phyla Proteobacteria, Choroflexi, and Actinobacteriota dominated the water and soil samples. In addition, three pathogenic genera were found in the surrounding soil and water samples. A metagenomic analysis identified 14 types of ARGs (>1%), with the highest proportion of multidrug ARGs at 47%. A total of 28 subtypes of ARGs were detected (>1%), with macB the most prevalent. The correlation analysis revealed that several key phyla, including Proteobacteria, Actinobacteria and Acidobacteria, were the main potential hosts and positively correlated with the ARGs. Efflux pumps (60-66%) were the primary resistance mechanism, and each resistance mechanism was distributed in similar proportions in the microbial community.