Complete Sequences of mcr-1-Harboring Plasmids from Extended-Spectrum-β-Lactamase- and Carbapenemase-Producing Enterobacteriaceae

Abstract

Here we completely sequenced four mcr-1-haboring plasmids, isolated from two extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli and two carbapenemase-producing Klebsiella pneumoniae clinical isolates. The mcr-1-harboring plasmids from an E. coli sequence type 2448 (ST2448) isolate and two K. pneumoniae ST25 isolates were identical (all pMCR1-IncX4), belonging to the IncX4 incompatibility group, while the plasmid from an E. coli ST2085 isolate (pMCR1-IncI2) belongs to the IncI2 group. A nearly identical 2.6-kb mcr-1-pap2 element was found to be shared by all mcr-1-carrying plasmids.

FIG 1

Structures of plasmids pMCR1-IncX4 and pMCR1-IncI2. (A) Comparison of IncX4 plasmids pSH146_32 (GenBank accession no. JX258655), pMCR1_IncX4 (KU761327, this study), and pJIE143 (JN194214); (B) comparison of IncI2 plasmids pHNSHP45 (KP347127) and pMCR1_IncI2 (KU761326, this study). Colored arrows represent open reading frames, with dark blue, yellow, green, red, purple, and orange arrows representing replication genes, mobile elements, plasmid transfer genes, the mcr-1 gene, other antimicrobial resistance genes, and plasmid backbone genes, respectively. Blue shading denotes regions of shared homology among different plasmids.

FIG 2

Genetic structure of mcr-1-harboring elements in selected plasmids. Plasmid incompatibility groups are noted on the left, along with the plasmids and/or strains harboring the genetic structure depicted. Arrows denote open reading frames (ORF), with red, gray, yellow, and white arrows denoting mcr-1, pap2, ISApl1, and neighboring genes, respectively. Following BLAST analysis of NCBI draft genomes, only contigs long enough to unambiguously identify plasmid replicon groups were included in this figure. The dashed yellow outline of the IncP ISApl1 ORF therefore indicates that only a partial sequence is available. The small black arrows adjacent to ISApl1 denote the inverted reverse repeats (IRR). The GenBank accession numbers of the mcr-1 contig sequences for EC5, EC7, EC13, 2012CEB2196SAL, 2012CEB4337SAL, 2013LSAL02374, and 2013LSAL04524 are JWKF01000084, JWKG01000081, JUJZ01000081, LKJJ01000031, LKJK01000087, LNCZ01000024, and LKJD01000010, respectively.