Intestinal colonization of Enterohemorrhagic E. coil

描述（由申请人提供）：肠出血性大肠杆菌（EHEC）是一种新兴的食物和水传播病原体，定植在远端回肠和结肠并产生强毒性的细胞毒素。肠出血性大肠杆菌感染引起的疾病范围从轻微腹泻到可能致命的溶血性尿毒症综合征。这些细菌，特别是血清型O157:H7，对公共卫生构成重大威胁，被列为NIAID B类重点病原体。O157:H7基因组包含-1.4兆碱基的DNA，这些DNA不存在于非致病性大肠杆菌K-12的基因组中。这些额外的DNA散布在与大肠杆菌K-12共有的序列的主干上，形成177个“o岛”。我们的中心假设是o型岛编码了大肠杆菌O157:H7的大部分致病特性。所有报道的肠出血性大肠杆菌毒力因子都在o岛编码，我们最近发现了一个额外的o岛编码因子AcfO，它促进肠出血性大肠杆菌的肠道定植。我们已经开发了快速和全面调查未表征的o型岛对肠出血性大肠杆菌致病性的贡献的方法。虽然大肠杆菌O157:H7与体外哺乳动物细胞的相互作用已被广泛研究，但对肠道定植所需的肠出血性大肠杆菌因子知之甚少。我们知识上的这一差距主要是由于缺乏现成的人类肠出血性大肠杆菌感染动物模型。我们的初步数据表明，幼兔是研究大肠杆菌O157:H7感染肠道表现的良好模型宿主。幼兔出现腹泻和结肠炎，可进行肠道定植定量分析。在本提案中，我们将利用幼兔对单个o岛缺失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，我们将鉴定肠出血性大肠杆菌促进肠道定植的o岛基因。我们研究这些基因产物的作用机制的方法是通过Aim II中提出的实验来说明的，在Aim II中，我们将描述acfO的表达、调控、功能、传递和分布。这些研究将产生有关肠出血性大肠杆菌致病性机制的有价值的新信息，并确定可能为新疗法和疫苗提供新靶点的定植因子。

DESCRIPTION (provided by applicant): Enterohemorrhagic Escherichia coli (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 DNA that are not present in the genome of non-pathogenic E. coli K-12. This additional DNA is interspersed as 177 'O-islands' along the backbone of sequences that are shared with E. coli 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.