In recent years, antibiotic resistance genes (ARGs) in aquatic environments have emerged as a significant challenge to public health security. While previous studies have primarily focused on the prevalence and distribution of ARGs in rivers, their spatial variation, environmental risks and sources along river systems have not been systematically investigated. This study comprehensively examined the distribution, variation trend, and sources of ARGs pollution along the lower reaches of the Yangtze River. The results revealed that the predominant ARG types in the lower Yangtze River conferred resistance to multidrug, macrolide, and tetracycline antibiotics. ARG abundances increased from the upstream to the midstream but were the lowest in the downstream region. Aquaculture and livestock production were identified as the major contributors to ARG variance. At the phylum level, Proteobacteria and Actinobacteria were the primary potential hosts of ARGs. Environmental risks associated with ARGs were higher in midstream river water and sewage discharge points. Linear regression analysis indicated significant positive correlations between the diversity of both ARGs and their host communities and the abundance of mobile genetic elements (MGEs). Source analysis further demonstrated that the three most abundant ARG types of ARG in downstream river, multidrug, MLS, and tetracycline resistance genes were co- influenced by upstream river water and sewage inputs, with river water contributing a higher proportion (64.83% -73.39%). The findings provide important data to support the development of strategies for monitoring and controlling ARG pollution in the lower Yangtze River. • Totally 891 unique ARGs belonging to 21 antimicrobial classes were identified in the river system. • Pseudomonas and Actinomycetota were important host of ARGs at phylum level for both river and wastewater samples. • Source tracking revealed that upstream river water significantly influenced the distribution of multidrug, MLS, and tetracycline resistance genes downstream in the lower reaches of the Yangtze River.
Jia et al. (Sun,) studied this question.