Contamination profiles of antibiotic resistance genes in the sediments at a catchment scale

•ARGs of tetracycline, sulfonamide, macrolide, and integrons detected in sediment•sul2 was the highest resistance gene and the intI2 was found to be the lowest.•The distribution of ARGs was correlated to the sediment properties.•Sediment is a reservoir of ARGs and plays a key role in disseminating ARGs in basin.

The aim of this study was to investigate the contamination profiles of tetracycline, sulfonamide, and macrolide resistance genes, as well as integrons in sediments of Dongjiang River basin of South China by real time quantitative polymerase chain reaction. sul2 was the most abundant resistance gene, with the average concentration of 6.97 × 108 copies/g and 1.00 × 108 copies/g in the dry and wet seasons, respectively, followed by ermF, sul3, sul1, intI1, tetA, ermB, tetX, tetM, tetQ, tetO, tetW, tetS, ermC, and tetB. The abundance of intI2 gene was the lowest in the sediment samples. Significant correlations existed between the ARGs and sediment properties as well as metals (Cu and Zn) and corresponding antibiotic classes, suggesting that the contamination of ARGs is related to chemical pollution of the sediments in the river basin. Principal component analysis showed distinct groupings of the sampling sites, reflecting that human activities are the key player in the dissemination of ARGs in the catchment environment.

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