Overlooked fate and associated pathogens of antimicrobial resistance in the Yellow River Delta, China

The spread of antibiotic resistance genes (ARGs) within terrestrial inputs and marine dispersal in estuarine deltas has posed significant environmental challenges, exacerbated by diverse microbial habitats, estuarine eutrophication, and other anthropogenic impacts. However, the precise mechanisms governing persistence and associated risks of ARGs in this region remain poorly understood. In this study, the distribution, mobility, removal and hosts of ARGs in wetlands and rivers of the Yellow River Delta (YRD) region were systematically investigated through metagenomic approaches. A total of 23 antibiotics were detected in water (0.07-4.67 ng/L) and 14 antibiotics in sediment (0.0042-0.4768 ng/g). Following wetland treatment, despite a 67.5% reduction in antibiotic concentrations, the relative abundance of antibiotic resistance genes decreased by only 7.60%, indicating substantial persistence of genetic resistance. Moreover, Proteobacteria were identified as primary hosts for ARGs. ARGs carried by resistant pathogens, especially ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), also showed a significant reduction in the abundance and diversity throughout the wetland. Notably, total nitrogen in water (Water-TN) greatest shaped the composition of the resistome and microbiome, while the presence of antibiotics exerted stronger selective pressure on ARGs in wetland than in river. Collectively, this study highlights the associated risks of ARGs in YRD, offering insights for controlling antimicrobial resistance in deltas.