奇异变形杆菌临床株对碳青霉烯类耐药的分子机制和同源性

Molecular mechanisms and clonal relatedness of carbapenem-resistant Proteus mirabilis clinical isolates

目的探讨ICU患者耐碳青霉烯类奇异变形杆菌临床株的分子机制和同源性。方法5株奇异变形杆菌分离自ICU患者的痰液或尿液。菌株的鉴定和药敏实验采用梅里埃VITEK 2Compact系统;PCR方法首先扩增菌株编码碳青霉烯酶基因,然后基于Illumina Miseq和Nanopore MinION技术获得菌株的全基因组序列,并用ResFinder等软件分析耐药基因和移动元件;菌株之间的同源性检测采用脉冲场凝胶电泳(PFGE);菌株的碳青霉烯基因定位则通过S1核酸酶切脉冲场凝胶电泳(S1-PFGE)和WGS(whole-genome sequencing)。结果这5株奇异变形杆菌的耐药表型和基因型一致,都携带blaNDM-1、blaTEM-1、blaCMY-2和blaOXA-1基因。依据Tonover规则,脉冲场凝胶电泳结果表明这5株菌间存在克隆聚集性。基因组测序和S1核酸酶切脉冲场凝胶电泳结果都证明blaNDM-1基因位于菌株的染色体上。结论结果表明在ICU存在染色体上携带blaNDM-1、blaTEM-1、blaCMY-2和blaOXA-1基因的奇异变形杆菌的克隆传播。

Objective The aim of this study was to investigate the molecular mechanisms and clonal relatedness of carbapenem-resistant Proteus mirabilis strains isolated from patients hospitalized in a intensive care unit(ICU).Methods Five Proteus mirabilis isolates were recovered between August 2019and September 2019from the clinical sputum or urine culture.The identification and antimicrobial susceptibility tests of these strains were determined by VITEK-2 Compact system.The carbapenemase encoding genes were detected using PCR and sequencing.Then whole-genome sequencing of these isolates were conducted by Illumina Miseq and Nanopore MinION technologies.The resistance genes and mobile elements were identified with ResFinder and other softwares.Clonality of the strains was assessed by pulsed field gel electrophoresis(PFGE).The genetic location of carbapenemase encoding gene was determined by nuclease S1-PFGE and WGS technologies.Results The five Proteus mirabilis isolates shared an identical phenotypic and genotypic profiles and harbored blaNDM-1,blaTEM-1,blaCMY-2and blaOXA-1genes.These strains were also found clonally-related with each other by PFGE according to Tenover criteria.Both whole-genome sequencing and S1-PFGE showed that the genes encoding the carbapenemase NDM-1were located on the chromosome in the Proteus mirabilis isolates.Conclusion The results indicated that there was a clonal dissemination of Proteus mirabilis strains which harbored blaNDM-1,blaTEM-1,blaCMY-2and blaOXA-1in the intensive care unit.