Plasmid-mediated Colistin Resistance: What Do We Know?

Abstract

Polymyxins (polymyxin E/colistin and polymyxin B) are considered the last-resort therapy against carbapenem-resistant Enterobacterales; however, the resistance of Enterobacterales to polymyxins is increasing worldwide. Until 2015, this resistance was related to chromosomal mutations, but in November 2015, it was described in China the transferable colistin resistance in animals and humans isolates of E. coli and K. pneumoniae, mediated by the mcr-1 gene (mobile colistin resistance), located in a plasmid. Following the first description of the mcr-1 gene, it has been reported in several regions of the world, in different bacterial species, from different sources and others mcr variants have been described. Moreover, the co-occurence of the mcr gene and other antimicrobial resistance genes was reported. This discovery changed the scenario of resistance to polymyxins, as this gene could be promptly disseminated among Gram negative bacilli becoming a major concern for public health. This review summarizes recent data about the plasmid-borne mcr colistin resistance gene.