Abstract: The emergence of the plasmid-borne colistin-resistant gene (mcr-1 ) poses a great threat to human health. What is worse, the recent observations of the co-existence of mcr-1  with other antimicrobial resistance genes in some bacteria cause further concern. Here, we present the first report of a wild Escherichia coli  strain that co-carries an mcr-1  encoding phage-like IncY plasmid (pR15_MCR-1) and a bla _NDM-5 encoding IncX3 plasmid (pR15_NDM-5) from a pharmaceutical industry, wastewater treatment plant, in China. This study highlights the spreading of E. coli  carrying both mcr-1  and bla _NDM-5 genes in the pharmaceutical industry.
Importance: Escherichia coli  strains that carry both mcr-1  and bla _NDM-5 genes are of great health concern and are already found in humans and animals worldwide, yet there is a paucity of observations of this resistant strain in the environment. Here we present the first isolation of an E. coli  strain (R15) that co-carries mcr-1  and bla _NDM-5 genes from a wastewater treatment plant in China. Whole-genome sequencing indicated that R15 harbored two plasmids, pR15_MCR-1 and pR15_NDM-5, that carry mcr-1  and bla _NDM-5, respectively. The observation of this wild-derived E. coli  strain that carries mcr-1  and bla _NDM-5 genes simultaneously calls for the urgency to improve monitoring and reducing its further spreading.
Keywords: mcr-1 , bla _NDM-5, wastewater treatment plant, Escherichia coli