The frequency and dissemination of antibiotic-resistant bacteria (ARB) and the antibiotic-resistant genes (ARG) they harbor are significant public health problems worldwide. While the wide-spread increased use of antibiotics has amplified selection for ARB and ARG in aquatic environments, metals can also increase antibiotic resistance. Metal resistance has been frequently associated with antibiotic resistance; however, the actual role of metals on ARGs in drinking water distribution systems (DWDS) remains unknown. The main objective of this research is to determine how metals in DWDS impact ARB and ARGs in drinking water. The central hypothesis is that diverse metal species in drinking water are selecting for ARB and ARGs. We employed culture-dependent methods and molecular techniques to investigate the prevalence of heterotrophic ARB and ARGs in treated drinking water. Microcosms of drinking water or source water were spiked with increasing concentrations of zinc orthophosphate or copper chloride. During microcosm experiments heterotrophic ARB were quantified by direct plating on 9 different antibiotic containing R2A growth media. Following microcosm experiments, DNA was extracted and ARGs (ermF, ermB, blaSHV, qnrA, sul1, and intI1) were quantified via qPCR. Exposure to zinc orthophosphate increased the relative abundance of ciprofloxacin, streptomycin, and tetracycline resistant bacteria, and increased relative abundance of type I integron related genes (sul1 and intI1). The bacterial community in tap water exposed to copper had increased relative abundance of ampicillin, chloramphenicol, ciprofloxaxin, erythromycin, streptomycin, sulfamethoxazole, and trimethoprim resistant bacteria, and the genes intI1 and blaSHV. Collectively these results indicate that increased soluble zinc and copper can yield increased relative abundance of ARB and ARGs. This research will produce a better understanding of the selective environment generated by metals within a DWDS. These results can be used to for engineering decisions aimed at protection of public health.

Effects of metals on the relative abundance of antibiotic resistant bacteria in drinking water

255th National Meeting (2018)

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