Effects of a Mining Dam Disaster on Antimicrobial-Resistant and Metal-Tolerant Bacterial Strains Recovered from Environmental Samples

Anthropogenic activities are closely related to the emergence, spread, and evolution of antimicrobial resistance (AMR). In addition to the introduction of chemical pollutants into the environment, dam failure may contribute to the selection of AMR and metal tolerance, and horizontal gene transfer. In this context, environmental samples from unaffected and affected sites were analyzed to obtain bacterial strains and investigate AMR and metal tolerance, as well as antimicrobial resistance genes (ARGs) and metal tolerance genes (MTGs). A wide diversity of emerging bacterial pathogens has been detected, which are often associated with multidrug resistance and multimetal tolerance. Intrinsic and acquired ARGs and MTGs were identified in clinically important bacteria. Extended-spectrum β-lactamase-encoding genes were exclusive of Pseudomonas aeruginosa and Escherichia coli from sediments and soils of affected sites. Overall, P. aeruginosa, E. coli, and Klebsiella pneumoniae were the ones that presented ARGs and/or MTGs, as well as the coexistence of them, which increased in the affected sites. These findings support that mining pollution increased the amount of MTGs and that they co-occur with different ARGs in a great diversity of bacterial species.