Moraxella Species as Potential Sources of MCR-Like Polymyxin Resistance Determinants

Abstract

Plasmid-mediated resistance to polymyxins mediated by the MCR-1/2 determinants has been reported in Enterobacteriaceae worldwide. Using PCR-based and cloning strategies, a series of Moraxella spp. were screened for mcr-like genes. Moraxella spp. that are mainly animal pathogens but may also be human pathogens were identified as potential reservoirs of mcr-like genes.

Keywords: MCR; animal; plasmid; polymyxin; reservoir; resistance.

FIG 1

Sequence comparison of plasmid-mediated MCR-like determinants. The plasmid-mediated MCR-1 and MCR-2 determinants were published previously (6, 16). MCR-LIN is from M. lincolnii, MCR-CAT from M. catarrhalis, MCR-OSL from M. osloensis, and MCR-POR from M. porci. Slashes indicate identical amino acid residues. Shaded areas indicate conserved cysteine residues forming the three disulfide bridges of the MCR-1 catalytic domain (28). The threonine 285 that was shown to be the catalytic nucleophile in MCR-1 (28) is also conserved among all the MCR proteins, indicated by open boxes.

FIG 2

Phylogenetic tree obtained for a series of phosphoethanolamine transferase encoding genes (A) and 16S RNA genes (B) by the distance method using the neighbor-joining algorithm (SeaView v4 software) (40). Branch lengths are drawn to scale and are proportional to the number of amino acid changes with 200 bootstrap replications. The distance along the vertical axis has no significance.