Co-Existence of mcr-1 and blaNDM-5 in an Escherichia coli Strain Isolated from the Pharmaceutical Industry, WWTP

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 andbla(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.