Heterogeneous genetic location of mcr-1 in colistin-resistant Escherichia coli isolates from humans and retail chicken meat in Switzerland: Emergence of mcr-1-carrying IncK2 plasmids

Abstract

We characterized the genetic environment of mcr-1 in colistin-resistant Escherichia coli strains isolated in Switzerland during 2014 to 2016 from humans (n 3) and chicken meat (n 6). Whole-genome and plasmid sequencing identified the mcr-1 gene integrated in IncX4 (of which, one strain carried the mcr-1.2 variant), IncI2, IncHI2, and novel IncK2 plasmids (overall, n 7), as well as in the bacterial chromosome (n 2) in single or duplicate copies. Our study supports the easy mobilization of mcr-1 across diverse genetic locations.