Environmental Reservoirs, Genomic Epidemiology, and Mobile Genetic Elements

Antimicrobial resistance (AMR) is a serious threat to public health and the environment, as it reduces the effectiveness of treatments and increases the risk of life-threatening infections. AMR evolution is influenced by various factors, such as the presence and concentration of antimicrobial agents in microbial niches, the diversity and abundance of microbes, and the environmental conditions that affect their survival and growth. One of the main drivers of AMR evolution is horizontal gene transfer (HGT), which is the exchange of genetic material between different microbes. HGT can occur through different mechanisms, such as plasmids, phages, mobile elements, and other DNA fragments. These mechanisms allow microbes to acquire new genes that confer resistance to different antimicrobial agents, or to modify existing genes to enhance their resistance. It can also facilitate the spread of AMR genes among different microbes, both within and across species. The environmental reservoirs and natural conditions that affect AMR evolution and transmission are diverse and complex. Some examples of these reservoirs such as soil, water, plants, animals, and humans act as sources or sinks of AMR genes, depending on the balance between gene acquisition and gene loss. Natural conditions like temperature, pH, salinity, oxygen levels, nutrient availability, and microbial interactions affect AMR evolution and transmission. These conditions can modulate the expression and activity of AMR genes, as well as the fitness and competitiveness of resistant microbes. This chapter provides an overview of the major environmental reservoirs and natural conditions affecting AMR evolution, and evolution and transmission of antimicrobial resistance genes in environmental settings. It also discusses the challenges and opportunities for monitoring and controlling AMR in these settings, as well as the implications for human health and the environment.