By John M. Balbus
Antimicrobial resistance is not just a daunting global health problem; it is a daunting global environmental health problem. This is because antibiotics, their residues, and active metabolites are transported widely through the environment by a number of pathways. The problem is intensified by the fact that numerous antibiotics are used in massive quantities in animal agriculture, and that exposure to one antibiotic can sometimes lead to resistance to multiple antibiotics through gene linkages.
Two recent papers highlight the global environmental health aspects of antimicrobial resistance, taking a One Health approach. One Health emphasizes the connectivity between human health and the health of animal species, both domestic and wild. By studying patterns of resistance genes in animals, environmental samples, and humans, researchers have generated important questions about the role of environmental transmission and amplification in the global spread and intensification of antimicrobial resistance.
The first paper, published by Jing Wang et al. in Zoological Research, is a systematic review of the literature of resistance gene identification in wild animals. It documents the occurrence of Extended-Spectrum Beta Lactamase (ESBL)-producing Enterobacteriaciae bacteria in over 80 species of wildlife, mostly birds, as well as four other critical types of antimicrobial resistance genes (AmpC cephalosporinase, carbapenemase, and colistin resistance) in numerous wildlife species around the world. The paper notes that wildlife could serve as an important reservoir for antimicrobial resistance genes, and that the mobility of bird species could serve as an important mechanism of global spread of resistance.
The second paper, published by Purohit et al. in the International Journal of Environmental Public Health Research, describes a small study of a single village in the Indian state of Madhya Pradesh. Researchers took water samples from drinking water sources and nearby water bodies and stool samples from small children and domestic animals, all within a several-day period. They then isolated bacteria from these different sources to assess antibiotic resistance. They found similar patterns of resistance to a wide variety of antibiotics, including quinolones, carbapenems, cephalosporins, tetracyclines, and sulfonamides. They also found similar genetic transfer and rates of multidrug resistance among the various sources. The authors conclude that this kind of “one health” approach, which samples humans and non-human sources simultaneously, is important in monitoring antibiotic resistance in vulnerable communities and in developing stewardship programs.
Both papers together suggest that antimicrobial resistance interventions that focus solely on clinical usage and clinical settings may miss critical reservoirs of resistance and be limited in their effectiveness. Consideration of environmental reservoirs and a One Health approach that examines the role of wildlife in maintaining or transmitting resistance across distances are needed to fully understand and intervene in this crisis.