Dissemination of the mcr-1 colistin resistance gene

In their Comment on the Article by Yi-Yun Liu and colleagues about the emergence of plasmid-mediated colistin resistance involving the mcr-1 gene from bacteria isolated in China,1 David Paterson and Patrick Harris2 referred to our finding of colistin resistance in two Escherichia coli isolates from a pig and a human being in Laos that were indistinguishable by pulsed-field gel electrophoresis.3 Our results, suggested animal to human transmission for which no known chromosomally encoded colistin resistance mechanisms were identified, raising the question of a similar mechanism of colistin resistance to that identified by Liu and colleagues.