mcr-1.2, a new mcr variant carried on a transferable plasmid from a colistin-resistant KPC carbapenemase-producing Klebsiella pneumoniae strain of sequence type 512

A novel mcr variant, named mcr-1.2, encoding a Gln₃-to-Leu functional variant of MCR-1, was detected in a KPC-3-producing ST512 Klebsiella pneumoniae isolate collected in Italy from a surveillance rectal swab from a leukemic child. The mcr-1.2 gene was carried on a transferable IncX4 plasmid whose structure was very similar to that of mcr-1-bearing plasmids previously found in Escherichia coli and K. pneumoniae strains from geographically distant sites (Estonia, China, and South Africa).