Studies on Emergent Diarrheagenic E. coli Pathogens

描述(申请人提供)：儿童腹泻每年导致200万5岁以下儿童死亡，主要发生在服务不足的国家。大肠杆菌病原体被认为是仅次于轮状病毒的第二大死亡原因。已知六类致泻性大肠杆菌可引起腹泻，然而，我们小组最近的研究发现了一种新的致泻性类别，称为局部性粘附性大肠杆菌(LAEC)，它与南美洲哥伦比亚的儿童腹泻显著相关。这项研究的长期目标是了解这种新出现的LAEC病原体的流行病学和发病的分子机制。第一个具体目标建议通过开展两项国际多中心病例对照研究来评估LAEC与儿童腹泻的频率和相关性。我们假设LAEC与生活在发展中国家的5岁以下儿童的儿童腹泻有关。第二个具体目标将解释LAEC毒力因子是如何在人类感染的仔猪模型中导致疾病的关键。我们推测，IV型菌毛和一种新的III型分泌系统引导细菌细胞入侵与LAEC腹泻的发病直接相关。最后一个具体目标是对LAEC菌株进行基因组DNA测序分析，以确定导致LAEC作为病原体出现的遗传因素。我们假设LAEC共享共同的定义明确的毒力基因，这些基因是通过水平基因转移获得的。这个项目意义重大，因为它将带来关于LAEC流行病学、遗传学和发病机制的基础知识，并将产生分子生物学工具，促进LAEC腹泻流行病学、预防措施和疫苗开发研究的未来研究。

DESCRIPTION (provided by applicant): Childhood diarrhea leads to 2 million deaths every year among children less than 5 years of age mainly in underserved countries. E. coli pathogens are believed to be the second most common cause of death after Rotavirus. Six categories of diarrheagenic E. coli have been known to cause diarrhea, yet, recent studies by our group have identified a new diarrheagenic category designated localized adherent E. coli (LAEC) that is significantly associated with childhood diarrhea in Colombia, South America. The long term goal of this study is to understand the epidemiology and the molecular mechanisms of pathogenesis of this new LAEC emergent pathogen. The first specific aim proposes to evaluate the frequency and association of LAEC with childhood diarrhea by conducting two international multicenter case-control studies. We hypothesize that LAEC is associated with childhood diarrhea in children less than 5 years of age living in developing countries. The second specific aim will explain how LAEC virulence factors are essential to cause disease in a piglet model of human infection. We hypothesize that the type IV bundle-forming pilus and a novel type III secretion system directing bacterial-cell invasion are directly associated with the pathogenesis of LAEC diarrhea. The last specific aim will conduct genome DNA sequencing analysis of LAEC strains to identify the genetic elements that resulted in the emergence of LAEC as a pathogen. We hypothesize that LAEC shares in common well defined virulence genes that were acquired by horizontal gene transfer. This project if significant because it will bring fundamental knowledge on the epidemiology, genetics, and pathogenesis of LAEC and will generate molecular biology tools to facilitate future studies on LAEC diarrhea epidemiology, prevention measures and vaccine development research.