Extended-spectrum β-lactamases, carbapenemases and the mcr-1 gene: is there a historical link?

The plasmid mediated mcr-1 gene encoding for Enterobacteriaceae colistin resistance has been recently identified across five continents. The objective of the present study was to trace historical events concerning the discovery and emergence of the mcr-1 gene along with ESBL and carbapenemase genes since several studies have reported identifying mcr-1 genes among Extended-Spectrum β-Lactamases (ESBL) and/or carbapenemase producing Escherichia coli. A retrospective study reported the identification of the mcr-1 gene in E. coli strains isolated in the 1980s, and this seems to correspond to the first identification of ESBL enzymes. The first discovery of the New Delhi metallo-beta-lactamase-1 (NDM-1) in 2009 was associated with a significant increase in mcr-1 gene prevalence in E. coli strains obtained from food producing animals. We noticed that a historical link has existed between mcr-1, ESBL and carbapenemase genes since the 1980s, and we believe that the re-evaluation of colistin use in livestock needs an overall approach that includes not only colistin use reduction but also the reduction of all antibiotic use.