Fragmented Microplastics Synergize with Biological Treatment To Potentiate Antibiotic Resistance Dissemination during Sewage Treatment

Wastewater treatment plants (WWTPs) are important reservoirs for antibiotic resistance genes (ARGs) and microplastics (MPs), and serve as hotspots for antibiotic resistance spread. However, actual survey data on their combined pollution along the entire sewage treatment chain remain scarce. This study integrated metagenomic sequencing and high-throughput qPCR to analyze the correlation between ARGs and MPs. The results revealed that clinically relevant and rank I high-risk intracellular antibiotic resistance genes (iARGs) were significantly enriched in the plastisphere throughout the sewage treatment process, particularly on fragmented MPs. FEAST source-tracking analysis revealed that MP-bound iARGs and extracellular ARGs in the biologically treated sewage contributed to 13-43 and 25-39% of the corresponding iARGs and eARGs detected in the effluent, respectively. Fragmented MPs also colocalized ARGs, virulence factors, and mobile genetic elements, potentially facilitating plasmid-mediated gene transfer. Acinetobacter, the primary ARG host and detected across 75 WWTPs with high ARG load, may serve as an antibiotic resistance indicator. This study highlights MP-driven ARG dissemination in WWTPs and informs resistance control strategies.