Contribution of environmental factors on the distribution of antibiotic resistance genes in agricultural soil

Antibiotic resistance (AR) has become a potential concern to public health. It is mainly associated with the overuse and misuse of antibiotics in the environment. Several factors influence the development and dissemination of antibiotic resistance genes (ARGs); however, the relative contribution of these factors has been scarcely characterized. To study the impact of each factor, we examined the effects of five antibiotics, eight heavy metals, five physicochemical properties, and bacterial community on the abundance of 310 ARGs in agricultural soils collected near a smelter. Tetracycline was found in the highest levels of all the samples compared to the other four antibiotics, with the most severe contamination (1738.534 μg/kg) occurring in the sample farthest from the plant (2556 m), whereas the highest copy number of ARGs (sulfonamide resistance genes, 3.63 × 10−1 copies/16SrRNA) and the worst heavy metal pollution (Cd, 18.900 mg/kg; Pb, 1938.000 mg/kg) were detected in the sample closet to the plant (741 m). Pearson and Spearman rank correlation analysis showed that the abundance of 84 ARGs was impacted by these four factors in the soil. The bacterial phyla contributed to 79.76% of ARGs variation, whereas antibiotics, heavy metals, and physicochemical properties contributed 4.76%, 1.19%, and 3.57%, respectively. Bacterial community was the main factor influencing the distribution of ARGs. Antibiotics and heavy metals may affect the distribution of ARGs not only by themselves but also by influencing the structure of bacterial community in the soil. The research provides insights into the different contributions of factors to AR control.