Spread of antibiotic resistance in the environment: Impact on human health

Abstract

Antibiotic-resistant pathogenic bacteria pose a high threat to human health, but the environmental reservoirs of resistance genes are poorly understood. The origins of antibiotic resistance in the environment are relevant to human health because of the increasing importance of zoonotic diseases as well as the requirement for predicting emerging resistant pathogens. Only little is known about the antibiotic resistomes of the great majority of environmental bacteria, although there have been calls for a greater understanding of the environmental reservoirs of antibiotic resistance. The data on antibiotic resistance before the antibiotic era and in soil show how far away we are from a complete picture about the ecology of antibiotic resistance genes (ARGs). Most of the natural antibiotic producers reside in soil, but soil is a particularly challenging habitat due to its chemical and physical heterogeneity. The prevalence and diversity of ARGs in the environment led to hypotheses about the native roles of resistance genes in natural microbial communities. This chapter gives an overview on the occurrence of antibiotic resistance determinants in different environments, discusses the environmental sources, the functions and roles of resistance determinants in microbial ecology, and the ways by which those genes may be disseminated in response to human antibiotic use. It also describes molecular methodologies used to study antibiotic resistance dissemination in the environment and attempts to assess the risks associated with resistance spread in the environment for human health.