Environmental fate of antibiotic resistance genes in livestock farming

Abstract

As emerging environmental pollutants, antibiotic resistance genes (ARGs) are prevalent in livestock farms and their surrounding environments. Although existing studies have focused on ARGs in specific environmental media, comprehensive research on ARGs within farming environments and their adjacent areas remains scarce. This review explores the sources, pollution status, and transmission pathways of ARGs from farms to the surrounding environment. Drawing on the "One Health" concept, it also discusses the potential risks of ARGs transmission from animals to human pathogens and the resulting impact on human health. Our findings suggest that the emergence of ARGs in livestock farming environments primarily results from intrinsic resistance and genetic mutations, while their spread is largely driven by horizontal gene transfer. The distribution of ARGs varies according to the type of resistance genes, seasonal changes, and the medium in which they are present. ARGs are disseminated into the surrounding environment via pathways such as manure application, wastewater discharge, and aerosol diffusion. They may be absorbed by humans, accumulating in the intestinal microbiota and subsequently affecting human health. The spread of ARGs is influenced by the interplay of microbial communities, antibiotics, heavy metals, emerging pollutants, and environmental factors. Additionally, we have outlined three control strategies: reducing the emergence of ARGs at the source, controlling their spread, and minimizing human exposure. This article provides a theoretical framework and scientific guidance for understanding the cross-media migration of microbial resistance in livestock farming environments.

Keywords: Farming environment; Manure; Resistance genes; Transmission pathways.