Large-scale metagenomic-based study of antibiotic resistance in the environment.

Antibiotic resistance, including multiresistance acquisition and dissemination by pathogens, is a critical healthcare issue threatening our management of infectious diseases [1-3]. Rapid accumulation of resistance phenotypes implies a reservoir of transferable antibiotic resistance gene determinants (ARGDs) selected in response to inhibition of antibiotic concentrations, as found in hospitals [1, 3-5]. Antibiotic resistance genes were found in environmental isolates, soil DNA [4-6], secluded caves [6, 7], and permafrost DNA [7, 8]. Antibiotics target essential and ubiquitous cell functions, and resistance is a common characteristic of environmental bacteria [8-11]. Environmental ARGDs are an abundant reservoir of potentially transferable resistance for pathogens [9-12]. Using metagenomic sequences, we show that ARGDs can be detected in all (n=71) environments analyzed. Soil metagenomes had the most diverse pool of ARGDs. The most common types of resistances found in environmental metagenomes were efflux pumps and genes conferring resistance to vancomycin, tetracycline, or β-lactam antibiotics used in veterinary and human healthcare. Our study describes the diverse and abundant antibiotic resistance genes in nonclinical environments and shows that these genes are not randomly distributed among different environments (e.g., soil, oceans or human feces).