Enterococcal Pathogenesis:Role of Cytolysin

描述（由申请人提供）：肠球菌已成为多重耐药医院感染的主要原因。 然而，它们作为寄生微生物存在了4亿多年，从昆虫到人类。 我们以前的工作，以及其他人的工作，已经表明，使医院分离的粪肠球菌更具毒性的因素之一是一种称为“溶细胞素”的毒素。“E. 粪菌溶细胞素具有抗菌特性，并且是人细胞的溶细胞毒素。我们先前表明，这种毒素导致感染死亡的风险增加了5倍，它与几个额外的毒力性状一起沿着在致病岛上传递，并且它的表达受到一种称为“趋化”的新过程的调节，该过程允许细菌检测附近靶细胞的存在，并产生大量毒素 虽然我们已经证明了E. 粪肠球菌溶细胞素毒素在结构和调控方面是新的，我们还不知道它如何影响人类感染的严重性，或在感染模型中，它使E.粪便感染多达100 急性毒性高出一倍。 我们也不知道“识别”在 转录水平。因此，我们建议确定毒素的抗菌特性是否允许E。 粪便进入胃肠道微生物群，是否由于抗菌活性而导致细菌组成的变化并在结肠内过度生长，是否通过其对哺乳动物细胞的细胞溶解活性损害结肠的屏障功能，或者它是否通过阻碍先天免疫系统从感染部位清除生物体而加剧感染。为了了解它的表达是如何调节的，我们还建议解剖新的双组分调节系统，这已被证明是必要的，其镇压和抑郁症。 这将通过定位溶细胞素操纵子转录起始的精确点，并确定这些起始位点与操纵子调控区结构特征之间的关系来完成。我们将确定导致高水平毒素表达的诱导信号是否从细胞外部传递，或者t是否被内化并直接导致操纵子抑制。 最后，我们将确定exactl如何每个调节蛋白相互关联，并涉及到溶细胞素操纵子的控制区域内的结构特征。 这些结果将为了解溶细胞素如何加重E. 粪便感染，以及 控制其表达所需的信息。

DESCRIPTION (provided by applicant): Enterococci have emerged as leading causes of multidrug resistant hospital infection. Yet they have existed as commensal microbes of everything from insects to man for over 400 million years. Our previous work, as well as the work of others, has shown that one of the factors that makes hospital isolate of Enterococcus faecalis more virulent is a toxin termed "cytolysin." The E. faecalis cytolysin has antibacterial properties, as well as being a cytolytic toxin for human cells. We previously showed that this toxin contributed a 5-fold increased risk of death from infection, that it was conveyed on a pathogenicity island along with several additional virulence traits, and that its expression is regulated by a novel process termed "telesensing" that allows the bacterium to detect the presence of target cells in the vicinity, and in respose produce high levels of the toxin. Although we have shown that the E. faecalis cytolysin toxi is novel in structure and regulation, we do not yet know how it contributes to the severity of infection in man, or in models of infection where it renders E. faecalis infection as much as 100 times more acutely toxic. We also do not know exactly how "telesensing" works at the level of transcription. Therefore, we propose to determine whether the antibacterial property of the toxin allows E. faecalis entry into the GI tract microbiota, whether it there causes changes in the bacterial composition and overgrows within the colon because of the antibacterial activity, whether it compromises the barrier function of the colon through its cytolytic activity for mammalian cells, or whether it exacerbates infection by impeding the innate immune system from clearing the organism from a site of infection. To understand how its expression is regulated, we also propose to dissect the novel two component regulatory system which has been shown to be necessary for its repression and depression. This will be done by mapping the precise points where transcription of the cytolysin operon is initiated, and determining the relationship between those start sites and structural features of the regulatory region of the operon. We will determine whether the inducing signal that results in high level toxin expression is communicated from the outside of the cell, or whether t is internalized and directly causes operon depression. Finally, we will determine exactl how each of the regulatory proteins relate to each other, and relate to structural features within the control region of the cytolysin operon. These results will provide needed information for knowing how the cytolysin exacerbates E. faecalis infection, as well as the information needed for controlling its expression.