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）会导致溶血性尿毒综合征（HUS），这是一种预后不良的严重并发症。肠出血性大肠杆菌的III型分泌系统（肠道定植机制）被认为是HUS发展的关键。然而，在由于血清型O 86 EHEC引起的家庭内感染的情况下，尽管大肠杆菌菌株不具有III型分泌系统，但受感染的儿童发展为HUS并死亡。本研究对O 86型肠出血性大肠杆菌的分子遗传学特性进行了研究。这些菌株具有编码弥散粘附因子（HdaA）的120.73-kb质粒（pO 86 A），并溶原化编码2型滋贺毒素（Stx 2）的60.238-kb噬菌体。pO 86 A还具有福氏志贺菌IgA 1型蛋白酶基因，并赋予对血清型O 86 EHEC菌株的粘膜免疫抗性。Stx噬菌体显示仅在O 86菌株中发现的插入位点的性质，而不是在O 157菌株中。这些结果支持以下假设：在儿童肠道中，血清型O 86特异性Stx 2噬菌体溶原化为高度定殖（弥漫粘附和产生IgA 1蛋白酶）的O 86大肠杆菌菌株，导致新的EHEC出现，引起致命的HUS。还得出结论，III型分泌对于HUS的发展不是必需的。此外，认为滋贺毒素诱导炎性细胞因子如IL-6和IL-8引起HUS。我们证明，中药山莨菪碱和抗菌剂azityhromycin，抑制这种炎症细胞因子的诱导，最有可能阻断NF-κ B活化途径。

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.