Non-biodegradable microplastics amplify antibiotic resistance and pathogen spread in bay plastisphere

Microplastics (MPs) serve as reservoirs that facilitate the dissemination of antibiotic resistance genes (ARGs) and human bacterial pathogens (HBPs), posing significant threats to public health. However, quantitative evaluations of high-risk ARGs in the plastisphere and comprehensive assessments of their associated health implications are still scarce. In this study, we employed in-situ incubation combined with high-throughput quantitative PCR and metagenomic sequencing to systematically compare the prevalence of ARGs, virulence factor genes (VFGs), mobile genetic elements (MGEs), and HBPs between biodegradable and non-biodegradable MPs. Our findings revealed a marked enrichment of ARGs, VFGs, MGEs, and HBPs in non-biodegradable MPs (polypropylene, polyethylene, and polystyrene) relative to the biodegradable MPs (polyhydroxyalkanoates, polylactic acid, and polybutylene adipate terephthalate). Furthermore, an integrated risk assessment combining high-risk ARGs quantification with a Projection Pursuit Regression model revealed significantly elevated microbial risks associated with non-biodegradable MPs. Taxonomic analysis further indicated that Pseudomonas and Aeromonas act as key HBP vectors carrying ARGs and VFGs in the plastisphere, underscoring their role in facilitating the spread of antimicrobial resistance and virulence. These results highlight how plastic properties mediate microbial colonization patterns under complex field conditions, providing a robust framework for environmental risk evaluation and the targeted management of plastic-associated biological hazards.