Detection of <i>mcr-1</i> Gene among Escherichia coli Isolates from Farmed Fish and Characterization of <i>mcr-1</i> -Bearing IncP Plasmids

Abstract

The presence of the <i>mcr-1</i> gene in <i>Escherichia coli</i> isolated from retail freshwater fish was investigated. Seven (3.65%) clonally unrelated original <i>E. coli</i> isolates from grass carp were positive for <i>mcr-1</i> The <i>mcr-1</i> genes were encoded by either chromosomes (<i>n</i> = 2) or conjugative plasmids (2 IncI2, 2 IncP, and 1 IncX4). The IncP plasmids were similar to other <i>mcr-1</i>-harboring IncP plasmids from China, though the insertion sites varied. Our report warrants further surveillance of resistance genes in aquaculture.