Genome Analysis of Emergence Mechanisms of New Enterohemorrhagic Escherichia coli and Genome-Based Drug Research toward HUS Treatment

儿童和老年人感染肠出血性大肠杆菌(EHEC)会导致溶血性尿毒症综合征(HUS)，这是一种严重的并发症，预后差。EHEC的III型分泌系统(肠道定植机制)被认为是HUS发生发展所必需的。然而，在O86型EHEC引起的家庭内感染的情况下，尽管大肠杆菌菌株没有III型分泌系统，但感染的儿童发生了HUS，并死亡。在本研究中，我们调查了O86型EHEC菌株的分子遗传学特性。这些菌株含有一个120.73 kb的质粒(PO86A)，编码一个弥漫性黏附因子(HdaA)，并能溶原2型志贺毒素(Stx2)的一个60.238 kb的噬菌体。PO86A还含有福氏志贺氏菌IgA1蛋白水解酶基因，对O86型EHEC菌株具有黏膜免疫抗性。STX噬菌体显示出仅在O86菌株中存在的插入位点的特性，而在O157菌株中未发现。这些结果支持这样一种假设，即在儿童的肠道中，O86血清型特异性Stx2噬菌体被溶原化为高度定植(扩散贴壁和产生IgA1蛋白酶)的O86大肠杆菌菌株，导致新的EHEC的出现，导致致命的HUS。我们还得出结论，III型分泌物对HUS的发展不是必需的。此外，志贺毒素还可诱导炎性细胞因子IL-6、IL-8等引起HUS。我们证明了中草药山梨碱和抗菌剂天青霉素抑制了这种炎性细胞因子的诱导，很可能阻断了核因子-kB的激活途径。

Infection of children and the elderly with enterohemorrhagic Escherichia coli (EHEC) results in hemolytic uremic syndrome (HUS), a severe complication with a poor prognosis. The type III secretion system (mechanism of intestinal colonization) of EHEC has been considered to be essential for the development of HUS. However, in case of intrafamilinal infection due to serotype O86 EHEC, although the E.coli strains do not have the type III secretion system, infected children developed HUS, and died. In this study, we investigated the molecular genetic properties of serotype O86 EHEC strains. These strains had a 120.73-kb plasmid (pO86A) encoding a diffuse adherence factor (HdaA), and lysogenized a 60.238-kb phage encoding type 2 Shiga toxin (Stx2). pO86A also had the Shigella flexneri type IgA1 protease gene, and conferred resistance to mucosal immunity to serotype O86 EHEC strains. The Stx phage showed properties of the insertion site found only in O86 strains, but not in O157 strains. These results support the hypothesis that in the intestinal tract of a child, serotype O86-specific Stx2 phage is lysogenized into highly-colonizing (diffusely-adhering and IgA1 protease-producing) O86 E.coli strains, resulting in the emergence of new EHEC, causing fatal HUS. It was also concluded that type III secretion is not essential for the development of HUS. Moreover, it is considered that Shiga toxin induces inflammatory cytokines such as IL-6 and IL-8 to cause HUS. We demonstrated that a Chinese herb, anisodamine, and an antimicrobial agent, azityhromycin, inhibited such an inflammatory cytokine induction, most probably blocking the NF-kB activation pathway.