Presence of high-risk ARGs with greater diversity and abundance in the rare resistome in wastewater across China.

Antibiotic resistance genes (ARGs) are widely recognized as hazardous materials that pose risks to public health. The core resistome, with its low ARG diversity yet accounting for the majority of the total ARG abundance, dominating the profile of antibiotic resistance. In this study, nationwide wastewater surveillance in China using metagenomic sequencing also identified a core resistome of 117 ARGs that accounted for 69.6 % of the total abundance. The emphasis of the work was to examine the rare resistome that included 1503 ARGs outside the core resistome. The abundances of clinically relevant ARG types (e.g., β-lactams and quinolones) were significantly higher in the rare resistome compared to the core resistome. Human pathogen-related ARGs were much greater in subtype number (96 vs. 34) and significantly higher in abundance (67.0 % vs. 33.0 %) in the rare relative to the core resistome, indicating that the rare resistome was the major contributor to the human pathogen resistome. The majority of ARG types accounting for the highest proportions of the rare resistome were plasmid-originated (65.5 %-100 %). In addition, human pathogen-related ARGs also had a significantly higher proportion of plasmid sources than non-pathogen ARGs, further highlighting their importance in wastewater-based surveillance.