Intestinal colonization of Enterohemorrhagic E. coil

肠出血性大肠杆菌(EHEC)是一种新出现的由食物和水传播的病原体 定植于远端回肠和结肠，并产生强烈的环毒素。EHEC感染导致多种疾病 从轻度腹泻到潜在致命的溶血性尿毒症综合征。这些细菌，特别是血清型 O157：H7对公众健康构成重大威胁，被归类为NIAID B类优先事项 病原体。O157：H7基因组含有-1.4兆碱基的DNA，这些DNA在O157：H7的基因组中是不存在的 非致病性E.coll K-12。这一额外的DMA以177个O-岛的形式散布在 与E.coll K-12共享的序列。我们的中心假设是O-岛编码了 大肠杆菌O157：H7的大部分致病特性。所有已报道的EHEC毒力因子都是 编码在O-岛，我们最近发现了另一个O-岛编码因子，AcfO，它促进 肠出血性大肠杆菌肠道定植。我们已经开发了方法来快速和全面地调查 未知O-岛对EHEC致病性的贡献。 虽然在体外对大肠杆菌O157：H7与哺乳动物细胞的相互作用进行了广泛的研究， 对肠道定植所需的EHEC因子知之甚少。我们的这一差距 这些知识主要是由于缺乏现成的人类EHEC感染的动物模型。我们的 初步数据表明，幼兔是研究肠道的良好模型宿主 大肠杆菌O157：H7感染的临床表现。幼兔出现腹泻和结肠炎，并 可以进行肠道定植的分析。在这个方案中，我们将利用幼兔来进行 对缺失单个O岛的肠出血性大肠杆菌突变体进行全面、高通量的筛选。在Aim I中，我们将 确定促进肠道定植的EHEC O-岛基因。我们的调查方法是 这里确定的基因产物的作用机制由AIM II中提出的实验来说明， 在这里我们将描述acfO的表达、调节、功能、传递和分布。这些 研究将产生关于EHEC致病机制的有价值的新信息，并识别 可能为新疗法和疫苗提供新靶点的定植因素。

Enterohemorrhagic Escherichia coll (EHEC) are an emerging group of food- and water-borne pathogens that colonize the distal ileum and colon and produce potent cytoxins. EHEC infection causes illnesses ranging from mild diarrhea to the potentially fatal hemolytic uremic syndrome. These bacteria, particularly serotype O157:H7, represent a significant threat to public health and are classified as NIAID Category B Priority pathogens. The O157:H7 genome contains -1.4 megabases of DMAthat are not present in the genome of non-pathogenic E. coll K-12. This additional DMA is interspersed as 177 'O-islands' along the backbone of sequences that are shared with E. coll K-12. Our central hypothesis is that the O-islands encode the majority of the pathogenic properties of E. coli O157:H7. All the reported EHEC virulence factors are encoded in O-islands, and we recently identified an additional O-island encoded factor, AcfO, that promotes EHEC intestinal colonization. We have developed methodology to rapidly and comprehensively survey the contribution of uncharacterized O-islands to EHEC pathogenicity. Although the interaction of E. coli O157:H7 with mammalian cells in vitro has been extensively studied, relatively little is known about the EHEC factors that are required for intestinal colonization. This gap in our knowledge is primarily due to the lack of a readily available animal model of human EHEC infection. Our preliminary data demonstrates that infant rabbits are an excellent model host for study of the intestinal manifestations of E. coli O157:H7 infection. Infant rabbits develop diarrhea and colitis, and quantitative analysis of intestinal colonization can be performed. In this proposal, we will utilize infant rabbits to carry out a comprehensive, high throughput screen of EHEC mutants with single O-islands deleted. In Aim I, we will identify the EHEC O-island genes that promote intestinal colonization. Our approach for investigating the mechanisms of action of gene products identified here is illustrated by the experiments proposed in Aim II, where we will characterize the expression, regulation, function, transmission and distribution of acfO. These studies will yield valuable new information about the mechanisms of EHEC pathogenicity and identify colonization factors that may provide new targets for novel therapeutics and vaccines.