Hexaconazole enantiomers drive the dissemination and risks of antibiotic resistance genes in the soil-earthworm system.

Abstract

Chiral fungicides constitute a substantial proportion of commonly used pesticides; however, the spread of antibiotic resistance genes (ARGs) in agricultural settings under repeated exposure to different enantiomers is still unclear. Here, the prevalence and potential risks of ARGs were investigated in the soil-earthworm ecosystem when exposed to hexaconazole (HEX) enantiomers. Metagenomic analysis indicated that R-HEX and S-HEX facilitated the dissemination of ARGs in soil without earthworms, but this effect diminished with successive exposures. Notably, S-HEX exhibited a greater effect on ARG profiles compared to R-HEX. Furthermore, HEX enantiomers, particularly S-HEX, increased the mobility potential of ARGs and enhanced host pathogenicity, thereby contributing to elevated ecological risks. Specifically, exposure to the HEX enantiomer led to an enrichment of dominant pathogenic ARG hosts, such as Enterobacteriaceae. Importantly, earthworms alleviated the enantiomer-driven dissemination of ARGs and weakened their association with mobile genetic elements (MGEs). Overall, this study offers novel perspectives on the enantiomer-driven propagation of ARGs induced by the chiral pesticide hexaconazole in soil and highlights the role of earthworms in mitigating ARG contamination. These findings contribute significantly to the risk assessment and remediation strategies for chiral pesticides.