New variant of mcr-3 in an extensively drug-resistant Escherichia coli clinical isolate carrying mcr-1 and blaNDM-5

Abstract

A colistin- and carbapenem-resistant Escherichia coli clinical isolate was found to carry two plasmid-borne colistin-resistant genes, mcr-1 and the newly identified mcr-3, and a carbapenemase gene, blaNDM-5. mcr-3 is a new variant (mcr-3.5) in the isolate and encodes three amino acid substitutions compared with the original MCR-3. mcr-3 was carried by a TnAs3-like transposon on a self-transmissible IncP plasmid in the isolate, highlighting that mcr-3 may have widely spread.