Deciphering the drivers of antibiotic resistance gene transmission in the megacity: Co-occurring contaminants and bacterial community.

Urban waters are widely contaminated with co-occurring microplastics and antibiotics. Human-land interactions (e.g., wastewater discharge, stormwater runoff, and land use) drive contaminant distribution and antimicrobial resistance. Nevertheless, there is a lack of systematic research evaluating the role of co-occurring contaminants in shaping the spread of antibiotic resistance genes (ARGs). In this study, a metagenomic approach was used to characterize the diversity and distribution of ARGs based on contaminant co-occurring patterns. The random forests and partial least squares path model (PLS-PM) were used to identify and prioritize the factors impacting ARGs, leading to a thorough environmental health ecological risk evaluation. Industrial waters, especially pharmaceutical factories, were significant reservoirs and hotspots for the development of ARGs. Urban estuaries further gathered and amplified the effects of co-occurring contaminants, thereby enhancing the prevalence of ARGs. The potential spread of ARGs was dominated by contaminant co-occurring patterns in urban waters, whereas microbial communities dominated in sediments. Urban zoning comprehensively affected environmental health risks, indicating that environmental management strategies, such as controlling pollution sources and implementing remediation, should prioritize water bodies in agricultural areas and sediments in commercial/residential areas.