Wastewater treatment plants (WWTPs) are key sources of antibiotic resistance genes (ARGs) and microplastics (MPs) in aquatic environments. However, field data on ARG-MP copollution remain scarce, hindering environmental risk assessment of ARGs. This study used metagenomic sequencing and high-throughput qPCR to examine the composition and association of ARGs and MPs in sewage discharge-receiving waters. The results indicated that sewage discharge significantly increased the abundance of ARG-MP complexes in receiving waters, with fibrous and fragmented MPs exhibiting enhanced ARG enrichment and thereby serving as selective vectors for pathogens. Effluents promoted plasmid-mediated gene transfer and microbial functional shifts, driving intracellular ARG proliferation in the plastisphere. Fibrous and fragmented MPs showed strong co-occurrence patterns with ARGs, virulence factor genes, and mobile genetic elements, suggesting their role in antimicrobial resistance dissemination. A projection pursuit regression model indicated effluent-induced MP risk escalation at the estuary and downstream areas, which was associated with fragmented and polyamide MPs. Notably, WWTPs released substantial extracellular ARGs, with MPs potentially serving as a protective niche and a proliferative microenvironment. Here, we determined the role of WWTPs in shaping the aquatic resistome via MPs, which provides critical data for risk assessment and control strategies.
Keywords: enrichment; environmental risk; extracellular antibiotic resistance genes; intracellular antibiotic resistance genes; microplastics; proliferation.