A Novel mcr-1 Variant Carried by an IncI2-Type Plasmid Identified From a Multidrug Resistant Enterotoxigenic Escherichia coli.
A Novel mcr-1 Variant Carried by an IncI2-Type Plasmid Identified From a Multidrug Resistant Enterotoxigenic Escherichia coli.
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从多重耐药产肠毒素大肠杆菌中鉴定出 IncI2 型质粒携带的新型 mcr-1 变体
DOI：
10.3389/fmicb.2018.00815
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发表时间：
2018
影响因子：
5.2
通讯作者：
Song H
中科院分区：
文献类型：
--
作者：
Liu H;Zhu B;Liang B;Xu X;Qiu S;Jia L;Li P;Yang L;Li Y;Xiang Y;Xie J;Wang L;Yang C;Sun Y;Song H
在这项研究中，我们发现了一种新的动员粘菌素耐药（mcr-1）基因变异体，命名为mcr-1.9，这是从临床腹泻病例中的粘菌素耐药肠毒素大肠杆菌（ETEC）菌株中鉴定出来的。由于单核苷酸多态性（G→A），mcr-1.9基因与mcr-1的1036位不同，导致MCR-1蛋白序列中天冬氨酸残基被天冬酰胺残基（Asp 346 →Asn）取代。抗菌药物敏感性试验表明，携带mcr-1.9的ETEC菌株对最小抑菌浓度为4 μg/ml的粘菌素具有耐药性。质粒谱分析和接合实验也表明，mcr-1.9变异体可成功转移至E. coli菌株J53，表明该基因位于可转移的质粒上。基因组测序数据的生物信息学分析表明，mcr-1.9基因位于64，005 bp质粒（命名为pEC 26）上。发现该质粒与携带mcr-1的IncI 2型质粒pWF-5- 19 C（99%同一性和99%覆盖率）和pmcr 1-IncI 2（99%同一性和98%覆盖率）具有高度相似性。携带mcr-1.9的ETEC还显示出对9类抗生素的多药耐药性，并含有基因组序列分析表明的几种毒力和抗菌剂耐药基因。我们的报告首次在从人粪便样本中分离的ETEC中鉴定出一种新的mcr-1变体，引起了人们对人肠道植物群中存在更多此类变体的担忧。因此，我们认为在人肠道细菌群落中鉴定新的mcr-1变体至关重要，需要采取措施控制mcr-1及其变体在人肠道菌群中的传播。
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.