Chapter 17 - The environmental resistome: Human exposure, health risks, and research needs

Abstract

Antibiotic resistance is a global concern due to its environmental, ecological, and human health risks. Antibiotic resistance comprises of antibiotic resistance genes coding for resistance, antibiotic-resistant bacteria, and the associated virulence genes and mobile genetic elements. The human health impacts of antibiotic resistance have received significant policy, research, and public attention. Yet comprehensive reviews discussing the human health effects, exposure routes, and risk factors in both low-income and developed countries are still limited. The current review presents a Source-Pathway-Receptor-Impact/Consequence (SPRI/C) analysis of the humans health impacts of the environmental resistome. First, evidence on the origins, detection, and behaviour of environmental antibiotic resistomes is discussed. Second, the mechanisms of antibiotic resistance and environmental circulation including horizontal gene transfer are discussed. Then, the multiple human exposure pathways to the environmental resistome are discussed, including: (1) water and food ingestion, (2) inhaling air-borne antibiotic resistance, and (3) skin/dermal contacts with contaminated surfaces. Risk factors and risky behaviour predisposing humans to the health risks of antibiotic resistance in low-income countries are discussed. A critique of the data is presented showing that quantitative empirical evidence on the human health impacts of the environmental resistome is still weak and predominantly inferential. The Disability-Adjusted Life Years (DALYs) and Quantitative Microbial Risk Assessment (QMRA) are proposed as tools to acquire the quantitative evidence on human health impacts. Future directions and perspectives on the human health risks of antibiotic resistance, including several knowledge gaps, are discussed.