Isogenic strain of Escherichia coli O157:H7 that has lost both Shiga toxin 1 and 2 genes
Isogenic strain of Escherichia coli O157:H7 that has lost both Shiga toxin 1 and 2 genes
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DOI：
10.1128/cdli.8.4.711-717.2001
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发表时间：
2001-07-01
期刊：
影响因子：
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通讯作者：
Takeda, T
中科院分区：
文献类型：
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作者：
Feng, P;Dey, M;Takeda, T
从出血性结肠炎患者分离的大肠杆菌O 157：H7菌株在鉴别培养基上显示出两种略有不同的菌落形态类型。每种形态类型，命名为TT 12 A和TT 12 B，被分离，并且使用各种测定的血清学试验证实两种菌株均携带O 157和H7抗原。生化试验表明，菌株在AP 120 E分析上具有相同的谱，并且像典型的O 157：H7菌株一样，不发酵山梨糖醇或显示P-葡萄糖醛酸酶活性。多重PCR分析表明，TT 12 B不携带滋贺毒素1（Stx 1）或Stx 2的基因，而这些基因存在于TT 12 A中并产生毒素。除此之外，两种菌株均携带+93 gusA突变、肠溶血素的duster I ehxA基因和γ-内膜蛋白的eae基因，这些都是O 157：H7血清型的特征。表型分析证实两株菌均具有肠溶血素活性，并对HeLa细胞具有粘附和消退性损伤。多位点酶电泳分析表明，这些菌株在遗传上亲缘关系较近，属于同一克隆群。XbaI消化的基因组DNA的脉冲场凝胶电泳（PFGE）分型显示，这两种菌株有两条带不同，但具有90%的相似性，并聚集在同一进化枝中，检查的所有其他非产Stx的O 157：H7菌株聚集在一个主要进化枝中，该进化枝与产Stx的O 157：H7菌株不同。TT 12 B与TT 12 A除了产生Stx之外是相同的，并且其PFGE谱也与产生Stx的O 157：H7菌株的PFGE谱更密切相关，这表明TT 12 B通过缺失两个stx基因而衍生自TT 12 A。
An Escherichia coli O157:H7 strain isolated from a patient with hemorrhagic colitis was found to exhibit two slightly different colony morphology types on differential medium, Each morphological type, designated TT12A and TT12B, was isolated, and serological testing using various assays confirmed that both strains carried the O157 and the H7 antigens, Biochemical testing showed that the strains had identical profiles on AP120E analysis and, like typical O157:H7 strains, did not ferment sorbitol or exhibit P-glucuronidase activity. Analysis with a multiplex PCR assay showed that TT12B did not carry the gene for either Shiga toxin 1 (Stx1) or Stx2, whereas these genes were present in TT12A and the toxins were produced. Apart from that, both strains carried the +93 gusA mutation, the duster I ehxA gene for enterohemolysin, and the eae gene for gamma -intimin, which are all characteristics of the O157:H7 serotype. Phenotypic assays confirmed that both strains exhibited enterohemolysin activity and the attachment and effacing lesion on HeLa cells. Multilocus enzyme electrophoresis analysis showed that the strains are closely related genetically and belong in the same clonal group. Pulsed-field gel electrophoresis (PFGE) typing of XbaI-digested genomic DNA revealed that the two strains differed by two bands but shared 90% similarity and clustered in the same clade, All other non-Stx-producing O157:H7 strains examined clustered in a major clade that was distinct from that of Stx-producing O157:H7 strains. The findings that TT12B was identical to TT12A, except for Stx production, and its PFGE profile is also more closely related to that of Stx-producing O157:H7 strains suggest that TT12B was derived from TT12A by the loss of both stx genes.