Identification of novel mobile colistin resistance gene .

Mobile colistin resistance () genes represent an emerging challenge. Here we describe a novel gene, , on an IncFIA plasmid of an clinical strain. has the highest nucleotide identity (79.69%) with and encodes MCR-10 with 82.93% amino acids identical to MCR-9. confers 4-fold increase in colistin MIC (from 1 to 4 mg/L) when cloned into a colistin-susceptible strain. By screening GenBank, was found in various species of countries in four continents, suggesting that this gene has widely spread. MCR-10 shows 79.04% to 83.67% amino acid identity and highly conserved predicted protein structures with chromosomally encoded MCR-like phosphoethanolamine transferases (designated MCR-B here) of various species. MCR-10, MCR-9 and MCR-B proteins may, therefore, originate from a common ancestor. was adjacent to a site-specific recombinase-encoding gene and was bracketed by IS and may be mobilized by site-specific recombination or composite transposon. Our results indicate that is a novel plasmid-borne colistin resistance gene and warrants immediate monitoring and further studies.