IncX4 Plasmid-Mediated <i>mcr-1.1</i> in Polymyxin-Resistant <i>Escherichia coli</i> from Outpatients in Santa Catarina, Southern Brazil

Abstract

Plasmid-mediated polymyxin resistance has become a global health concern, not only because its dissemination has occurred drastically but also because it has begun to be reported in multidrug-resistant (MDR) pathogens. We hereby report microbiological and genomic characteristics of two <i>mcr-1.1</i>-positive polymyxin-resistant <i>Escherichia coli</i> isolates identified for the first time in community patients, in Santa Catarina, Southern Brazil. <i>E. coli</i> strains belonging to ST206 and ST354 and the resistome analysis revealed the presence of clinically important genes responsible for MDR profile. Interestingly, in both polymyxin-resistant <i>E. coli</i> strains, <i>mcr-1.1</i> genes were carried by IncX4 plasmids, responsible for the worldwide dissemination of <i>mcr-</i>type genes. In this regard, plasmid backbones were almost identical to the first IncX4 plasmid reported in Brazil and sharing more than 99.9% identity to IncX4 plasmids from China, also lacking the ISApl1 insertion sequence upstream of <i>mcr-1</i>. In conclusion, these data confirm the presence of international ST206 and ST354 carrying <i>mcr-1.1</i> genes and that the IncX4 plasmids have been key vectors contributing to the endemic status of <i>mcr-1.1</i>-positive polymyxin-resistant <i>E. coli</i> in Brazil. Also, we described the first known clinical isolate with the <i>mrc1.1</i> gene in Santa Catarina state, Brazil, showing that plasmid-mediated polymyxin resistance has been affecting humans earlier than has been known so far.