Colistin resistant Escherichia coli harbouring mcr 1 isolated from food animals in Hanoi, Vietnam.
286 www.thelancet.com/infection Vol 16 March 2016 consistent with it being nested within an ISApl1 composite transposon (figure) IS1294 uses a one ended, rolling circle transposition mechanism capable of mobilising adjacent sequences. We postulate that mcr 1 was originally introduced into the ISApl1 element by IS1294, which was subsequently lost. We have identifi ed mcr 1 in a human faecal E coli isolate in Cambodia taken 2 years before the human isolates were collected in the study by Liu and colleagues, and which is associated with diff erent genetic structures than those reported by Liu and colleagues. IS1294 mediated transposition of the gene into an ISApl1 composite transposon may have represented the original import mechanism of mcr 1 into Enterobacteriaceae. Large, established databases of whole genome sequences represent a rich repository to investigate the historical presence of novel resistance mechanisms.
The Lancet. Infectious diseases