西安地区3株产二元毒素ST5型艰难梭菌基因组特征

Genomic characteristics of 3 strains of binary toxin-producing Clostridium difficile ST5 in Xi'an

  • 摘要: 目的 了解西安地区产二元毒素艰难梭菌的耐药基因、毒力基因和移动遗传元件的分子特征。方法 应用二代和三代测序仪对临床分离的3株ST5艰难梭菌(CD2019008、CD2022013和CD2023025)进行测序,使用Prokka软件对测序结果进行注释,Easyfig软件对PaLoc和CdtLoc区域的序列进行分析,Abricate软件预测耐药基因和毒力基因,E-test药敏条检测3株艰难梭菌的药物敏感性,使用ICEscreen、ISEScan、PlasmidFinder和噬菌体搜索工具来分析移动遗传元件。结果 3株艰难梭菌基因组大小范围4.07~4.15 Mbp,与RT027/ST1和RT078/ST11菌株相比,3株ST5菌株携带的PaLoc区域更大且插入了Tn6218转座元件,编码了截短的TcdC蛋白。同时含有完整的二元毒素编码及调控基因,这些基因与RT027/ST1菌株具有高度同源性。除携带有tcdA、tcdB和cdtA/B毒素基因,还携带有6个细胞黏附基因、1个胞外酶基因和5个耐药基因,3株艰难梭菌对环丙沙星均耐药,菌株CD2019008对左氧氟沙星耐药,对其余药物均敏感。2株艰难梭菌鉴定出了ICEs和IMEs,插入序列IS优势家族为IS200/IS605结论 通过对3株产二元毒素艰难梭菌的全基因组特征分析,并与流行株027和078型进行比较,本研究揭示了ST5型菌株的毒力与耐药基因谱、移动遗传元件特征及其特有的转座子Tn6218。该菌株具备成为高毒力优势流行株的潜力,应加强对ST5型艰难梭菌的监测与研究。

     

    Abstract: OBJECTIVE To investigate the molecular characteristics of antimicrobial resistance genes, virulence genes, and mobile genetic elements (MGEs) in binary toxin-producing Clostridium difficile strains in Xi'an. METHODS The three strains of clinical ST5 C. difficile isolates (CD2019008, CD2022013 and CD2023025)were sequenced. The sequencing results were interpreted by Prokka software, the sequences at PaLoc and CdtLoc regions were analyzed by Easyfig software, the drug resistance gens and virulence genes were predicted by Abricate software; the antimicrobial susceptibilities of the three strains of C. difficile were detected by E-test strips, and the MGEs were observed with the use of ICEscreen, ISEScan, PlasmidFinder and phage search tools. RESULTS The genome sizes of the three strains of C. difficile ranged from 4.07 to 4.15 Mbp. The three strains of ST5 isolates carried larger PaLoc region than the RT027/ST1 isolates and RT078/ST11 isolates and were inserted with Tn6218 transposable element and encoded a truncated TcdC protein. They harbored complete binary toxin encoding and regulatory genes, which showed high homology with those in the RT027/ST1 strains. In addition to the toxin genes tcdA, tcdB, and cdtA/B, the strains carried 6 cell adhesion genes, 1 extracellular enzyme gene, and 5 antimicrobial resistance genes. All of the three strains of C. difficile were resistant to ciprofloxacin; the strain CD2019008 was resistant to levofloxacin but was sensitive to other antibiotics. ICEs and IMEs were identified in two strains of C. difficile, and the predominant family of inserted sequence (IS) was IS200/IS605. CONCLUSIONS The virulence and drug resistance gene spectrum, characteristics of MGEs and peculiar transposon Tn6218 are revealed in the study through the analysis of whole genomic characteristics of the three strains of binary toxin-producing C. difficile and comparison with the prevalent strains of type 027 and 028. The strain possesses the potential to emerge as a hypervirulent predominant strain, and it is necessary to strengthen the surveillance and study of ST C. difficile.

     

/

返回文章
返回