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A Novel mcr-1 Variant Carried by an IncI2-Type Plasmid Identified From a Multidrug Resistant Enterotoxigenic Escherichia coli

By Hongbo Liu, Hongbo Liu, Binghua Zhu, Binghua Zhu, Beibei Liang, Beibei Liang, Xuebin Xu, Shaofu Qiu, Leili Jia, Peng Li, Lang Yang, Lang Yang, Yongrui Li, Ying Xiang, Ying Xiang, Jing Xie, Ligui Wang, Chaojie Yang, Yansong Sun and Hongbin Song and Hongbin Song

Abstract

In this study, we discovered a novel mobilized colistin resistance (mcr-1) gene variant, named mcr-1.9, which was identified in a colistin-resistant enterotoxigenic Escherichia coli (ETEC) strain from a clinical diarrhea case. The mcr-1.9 gene differs from mcr-1 at position 1036 due to a single nucleotide polymorphism (G→A), which results in an aspartic acid residue being replaced by an asparagine residue (Asp346→Asn) in the MCR-1 protein sequence. Antimicrobial susceptibility testing showed that the mcr-1.9-harboring ETEC strain is resistant to colistin at a minimum inhibitory concentration of 4 μg/ml. Plasmid profiling and conjugation experiments also suggest that the mcr-1.9 variant can be successfully transferred into the E. coli strain J53, indicating that the gene is located on a transferable plasmid. Bioinformatics analysis of data obtained from genome sequencing indicates that the mcr-1.9 gene is located on a 64,005 bp plasmid which has been named pEC26. This plasmid was found to have high similarity to the mcr-1-bearing IncI2-type plasmids pWF-5-19C (99% identity and 99% coverage) and pmcr1-IncI2 (99% identity and 98% coverage). The mcr-1.9-harboring ETEC also shows multidrug resistance to nine classes of antibiotics, and contains several virulence and antimicrobial-resistance genes suggested by the genome sequence analysis. Our report is the first to identify a new mcr-1 variant in an ETEC isolated from a human fecal sample, raising concerns about the existence of more such variants in human intestinal flora. Therefore, we believe that an undertaking to identify new mcr-1 variants in the bacterial communities of human intestines is of utmost importance, and that measures need to be taken to control the spread of mcr-1 and its variants in human intestinal microflora

Topics: mobilized colistin resistance (mcr-1) gene, novel mcr-1 variant, clinical diarrhea, enterotoxigenic Escherichia coli (ETEC), multidrug resistance (MDR), Microbiology, QR1-502
Publisher: Frontiers Media S.A.
Year: 2018
DOI identifier: 10.3389/fmicb.2018.00815/full
OAI identifier: oai:doaj.org/article:6675277bbf3347d98cbeb3109005ae56
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