Regulation and Role in Pathogenesis of Megaplasmid-encoded Virulence Factors of Shiga Toxin producing Escherichia coli

产生志贺毒素的大肠杆菌(STEC)会导致人类严重的胃肠道感染，这可能会导致潜在的致命的全身并发症，如溶血性尿毒症综合征(HUS)。长期以来，STEC病的病理一直被认为是志贺毒素(STX)产生的直接原因。然而，越来越多的证据表明，STEC菌株引起严重疾病的能力各不相同。虽然特定菌株产生的STX的数量或亚型明显起作用，但染色体致病岛(PAI)或巨质粒上编码的假定辅助毒力因子也是重要的。该项目是一个正在进行的大型研究计划的一部分，该计划旨在确定STEC的毒力因素，并确定新型疫苗和药物的靶标。它将集中在STEC巨质粒编码的因子上，特别是那些来自缺乏肠细胞消失位点(LEE)的菌株的因子。李氏阴性的STEC巨粒比O157：H7等李氏阳性菌株的大得多(160kb比92kb)，并编码一些独特的蛋白，其致病机制尚不清楚。这里描述的项目的主要目的是确定这些巨质粒中的哪些基因在模拟体内发生的条件下表达。这将使我们能够针对单个基因进行突变，以便在动物模型中评估它们对发病的贡献。

Shiga toxin producing Escherichia coli (STEC) cause serious gastrointestinal infections in humans, which can lead to potentially fatal systemic complications, such as the haemolytic uraemic syndrome (HUS). The pathology of STEC disease has long been considered to be directly attributable to the production of Shiga toxin (Stx). However, there is increasing evidence that STEC strains vary in their capacity to cause serious disease. Although the amount or subtype of Stx produced by a given strain clearly plays a role, putative accessory virulence factors encoded on chromosomal pathogenicity islands (PAI) or megaplasmids are also important. This project is part of a large on-going research program aimed at characterizing virulence factors of STEC and identifying targets for novel vaccines and drugs. It will focus on factors encoded by the STEC megaplasmids, particularly those from strains that lack the locus of enterocyte effacement (LEE). LEE-negative STEC megaplasmids are much larger than those from LEE-positive strains such as O157:H7 (160 vs 92 kb), and encode a number of unique proteins whose role in pathogenesis is unknown. The principal aim of project described here is to identify which of these megaplasmid genes are expressed under conditions that mimic those which occur in vivo. This will enable us to target individual genes for mutagenesis, such that their contribution to pathogenesis can be assessed in animal models.