Arsenic and cadmium as predominant factors shaping the distribution patterns of antibiotic resistance genes in polluted paddy soils

Heavy metals have been recognized as potential factors driving the evolution and development of antibiotic resistance. However, the relative effects of cadmium (Cd) and arsenic (As) on the prevalence and distribution of antibiotic resistance genes (ARGs) remain unclear. We investigated the co-selection effects of Cd and As on ARGs in 45 paddy soils polluted by heavy metals, using high-throughput quantitative PCR. A total of 119 ARGs and 9 mobile genetic elements (MGEs) were detected in all samples. Regression analysis showed that the single pollution index (PIAs and PICd) and Nemerow integrated pollution index (NIPI) both had significant and positive correlations with ARGs (P < 0.05), indicating the co-selective effects of Cd and As on ARGs distribution. The significant correlations between bacterial taxa and different ARGs in network analysis revealed potential hosts of ARGs. Structural equation models indicated that the effects of As on ARGs were stronger than that of Cd. The profile of ARGs could be impacted by Cd and As indirectly by strongly affecting the bacterial abundance. Overall, this study extended our knowledge about the co-selection of Cd and As on ARGs in paddy soil, and had important implications for assessing the potential risks of ARGs in paddy soils.