Fibrous and Fragmented Microplastics Discharged from Sewage Amplify Health Risks Associated with Antibiotic Resistance Genes in Aquatic Environments

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.