Construction of the XZ113 delta eaeA, XZ113 delta stx2 and XZ113 delta ehxA mutants of STEC O18 XZ113 and their pathogenicity in mice
产志贺毒素大肠杆菌O18 XZ113 株主要毒力基因eaeA、stx2、ehxA 突变株的构建及其对小鼠的致病作用

Objective] To study the contribution of virulence genes of STEC O18 XZ113 isolate to the pathogenicity in mice.Methods] The eaeA,stx2 and ehxA knock-out mutants of STEC strain XZ113 were generated using λ-Red recombination system.Results] Bacterial adherence test showed that the eaeA mutant adhered to HEp-2 cells in a diffuse manner with no microcolony formation.Vero cells assay showed that the stx mutant had no cytotoxicity to Vero cells.Enterohemolytic activity test showed that the ehxA mutant lost the ability to express the enterohemolytic activity.Competition assay between the wild-type strain XZ113 and its mutants in vivo and in vitro showed that all mutants were mildly attenuated in vitro,but in vivo,XZ113△eaeA was moderate attenuated,XZ113△stx2 and XZ113△ehxA were all highly attenuated.Conclusions] These results indicate that the virulence factors encoded by the stx2 and ehxA genes were important for the pathogenesis of STEC O18 in mice.