Role of Tir and intimin in the virulence of rabbit enteropathogenic Escherichia coli serotype O103:H2
Role of Tir and intimin in the virulence of rabbit enteropathogenic Escherichia coli serotype O103:H2
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DOI：
10.1128/iai.68.4.2171-2182.2000
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发表时间：
2000-04-01
影响因子：
3.1
通讯作者：
Oswald, E
中科院分区：
文献类型：
--
作者：
Marchès, O;Nougayrède, JP;Oswald, E
属于 O103 血清群的附着和消除 (A/E) 兔肠道致病性大肠杆菌 (REPEC) 菌株是断奶兔腹泻的重要原因。与人类 EPEC 菌株一样，它们具有肠细胞消失位点，聚集了参与 A/E 病变形成的基因。此外，致病性 REPEC O103 菌株产生 Esp 依赖性但 Eae (intimin) 独立的宿主细胞细胞骨架改变，其特征是形成粘着斑复合物以及将肌动蛋白细胞骨架重组为束 应力纤维。为了研究 intimin 及其易位辅助受体 (Tir) 在 REPEC 致病性中的作用，我们使用了新构建的同基因 fir 无效突变体和先前描述的 eae 无效突变体。当人类 HeLa 上皮细胞被感染时，tir 突变体仍然能够诱导应力纤维的形成，正如之前报道的 eae null 突变体一样。当使用兔上皮细胞系 RK13 时，REPEC O103 产生经典的荧光肌动蛋白染色 (FAS) 效果，而 eae 和 tir 突变体均为 FAS 阴性。在兔结扎回肠环模型中，两种突变体均不能诱导 A/E 损伤。与紧密粘附在肠细胞上并破坏刷状缘微绒毛的亲本菌株相反，两种突变体的细菌都聚集在粘液中，而没有到达并破坏微绒毛。然后通过给断奶兔子口服接种来分析 intimin 和 Tir 的体内作用。尽管口服接种后3周，这两种突变株仍然存在于兔子的肠道菌群中，但两种突变株均未在接种的兔子中引起任何临床症状或显着的体重减轻，而亲本菌株导致90%的接种兔子死亡。尽管如此，感染这两种突变体的兔子的固有层中都存在炎症浸润，其中eae无效突变体的炎症反应更大。总之，我们已经证实了intimin在毒力中的作用，并且我们首次证明Tir也是体内致病性的关键因素。
Attaching and effacing (A/E) rabbit enteropathogenic Escherichia coli (REPEC) strains belonging to serogroup O103 are an important cause of diarrhea in weaned rabbits. Like human EPEC strains, they possess the locus of enterocyte effacement clustering the genes involved in the formation of the A/E lesions, In addition, pathogenic REPEC O103 strains produce an Esp-dependent but Eae (intimin)-independent alteration of the host cell cytoskeleton characterized by the formation of focal adhesion complexes and the reorganization of the actin cytoskeleton into bundles of stress fibers. To investigate the role of intimin and its translocated coreceptor (Tir) in the pathogenicity of REPEC, we have used a newly constructed isogenic fir null mutant together with a previously described eae null mutant. When human HeLa epithelial cells were infected, the tir mutant was still able to induce the formation of stress fibers as previously reported for the eae null mutant. When the rabbit epithelial cell line RK13 was used, REPEC O103 produced a classical fluorescent actin staining (FAS) effect, whereas both the eae and tir mutants were FAS negative. In a rabbit ligated ileal loop model, neither mutant was able to induce A/E lesions. In contrast to the parental strain, which intimately adhered to the enterocytes and destroyed the brush border microvilli, bacteria of both mutants were clustered in the mucus without reaching and damaging the microvilli. The role of intimin and Tir was then analyzed in vivo by oral inoculation of weaned rabbits. Although both mutants were still present in the intestinal flora of the rabbits 3 weeks after oral inoculation, neither mutant strain induced any clinical signs or significant weight loss in the inoculated rabbits whereas the parental strain caused the death of 90% of the inoculated rabbits. Nevertheless, an inflammatory infiltrate was present in the lamina propria of the rabbits infected with both mutants, with an inflammatory response greater for the eae null mutant, In conclusion, we have confirmed the role of intimin in virulence, and we have shown, for the first time, that Tir is also a key factor in vivo for pathogenicity.