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Characterization of Five Escherichia coli Isolates Co-expressing ESBL and MCR-1 Resistance Mechanisms From Different Origins in China - PubMed

  • ️Tue Jan 01 2019

Characterization of Five Escherichia coli Isolates Co-expressing ESBL and MCR-1 Resistance Mechanisms From Different Origins in China

Pei Zhang et al. Front Microbiol. 2019.

Abstract

Present study characterized five Escherichia coli co-expressing ESBL and MCR-1 recovered from food, food-producing animals, and companion animals in China. Antimicrobial susceptibility tests, conjugation experiments, and plasmid typing were performed. Whole genome sequencing (WGS) was undertaken for all five isolates using either PacBio RS II or Illumina HiSeq 2500 platforms. The cefotaxime and colistin resistance encoded by bla CTX-M and mcr-1 genes, respectively, was transferable by conjugation either together or separately for all five strains. Interestingly, the ESBL and mcr-1 genes could be co-selected by cefotaxime, while the colistin only selected the mcr-1-carrying plasmids during the conjugation experiments. Five E. coli sequence types (ST88, ST93, ST602, ST162, and ST457) were detected. Although diverse plasmid profiles were identified, IncI2, IncFIB, and IncFII plasmid types were predominant. These five clonally unrelated isolates harbored the mcr-1 gene located on similar plasmid backbones, which showed high nucleotide similarity to plasmid pHNSHP45. The mcr-1 gene can be co-transmitted with bla CTX-M genes through IncI2 plasmids with or without ISApl1 in our study. Characterization of these co-existence ESBL and mcr-1 isolates extends our understanding on the dissemination of these resistance markers among bacteria of diverse origins.

Keywords: ESBL; Escherichia coli; co-occurrence; conjugative plasmids; mcr-1 gene.

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Figures

FIGURE 1
FIGURE 1

A heat-map showing the comparison of the five Escherichia coli donors and the resultant transconjugants, characterized on the basis of their plasmid profiles according to the S1-PFGE results; ESBL- and mcr-1-markers identified by PCR; antimicrobial resistance profile; and plasmid replicon type(s). The MIC for colistin in each group combination is also shown. (T) in the first column typifies the transconjugant. C and M in the first column typifies cefotaxime and colistin, respectively. Black and white squares denote the presence and absence, respectively, of a particular feature. Antimicrobial compounds are abbreviated as follows: AMP, ampicillin; CAZ, ceftazidime; CHL, chloramphenicol; CIP, ciprofloxacin; CTX, cefotaxime; CZO, cefazolin; GEN, gentamicin; IMP, imipenem; SXT, trimethoprim/sulfamethoxazole; TET, tetracycline; TGE, tigecycline.

FIGURE 2
FIGURE 2

(A) Major structural features of the mcr-1-harboring IncI2 plasmids in this study in comparison with the reference plasmid pHNSHP45 (Accession number KP347127). (B) Comparative schematic representation of the flanking regions of the mcr-1 genes in IncI2 plasmids. Areas shades in gray indicate homologies in the corresponding genetic environment on each plasmid. The ORFs are shown as boxes or arrows. Antibiotic resistance-encoding genes are indicated in red boxes/arrows. The individual conjugation-related genes are indicated with yellow boxes/arrows and the corresponding genes are indicated with capital letters inside the yellow boxes. Blue boxes/arrows denote transposon- and integron-associated genes. The putative virulence-related genes are indicated by violet boxes. The replication-associated genes are shown in green. White boxes/arrows indicate hypothetical proteins or mobile element proteins [The figures are not drawn to scale].

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