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【目的】探讨毒力基因eaeA、stx2、ehxA与产志贺毒素大肠杆菌O18致病力的关系。【方法】利用λ-Red重组系统,构建STEC XZ113株eaeA、stx2、ehxA基因缺失突变株并进行一系列生物学特性的研究。【结果】细胞粘附试验表明突变株XZ113△eaeA对HEp-2细胞的粘附能力明显降低;Vero细胞毒素试验表明突变株XZ113△stx2失去了使Vero细胞发生病变的能力;溶血活性试验表明突变株XZ113△ehxA无法在血平板上产生溶血圈,丢失了溶血能力。回复株在以上表型方面与野生株XZ113一致;与亲本株的体外竞争试验结果表明,突变株竞争力减弱,体内竞争结果表明突变株XZ113△eaeA被中度致弱;突变株XZ113△stx2和突变株XZ113△ehxA被高度致弱。【结论】stx2、ehxA基因在STEC O18 XZ113株的致病过程中发挥着更为重要的作用。
【Objective】 To investigate the relationship between virulence genes eaeA, stx2, ehxA and virulence of Shiga toxin-producing Escherichia coli O18. 【Method】 The eaeA, stx2 and ehxA deletion mutants of STEC XZ113 strain were constructed by λ-Red recombination system and a series of biological characteristics were studied. 【Results】 Cell adhesion assay showed that the adhesion ability of mutant strain XZ113 △ eaeA to HEp-2 cells was significantly reduced. Vero cytotoxicity assay showed that the mutant strain XZ113 △ stx2 lost the ability to cause Vero cells to develop lesions. Hemolytic activity test showed that the mutation Strain XZ113 △ ehxA can not generate hemolytic circle on the blood plate, losing the hemolytic ability. The results of in vitro competition with the parental strain showed that the competitiveness of the mutants was weakened and the in vivo competition results showed that the mutant strain XZ113 △ eaeA was moderately weakened. The mutant strains XZ113 △ stx2 and Mutant XZ113 △ ehxA is highly attenuated. 【Conclusion】 The stx2 and ehxA genes play a more important role in the pathogenesis of STEC O18 strain XZ113.