CONTROL OF ENTEROTOXIN GENE EXPRESSION IN S AUREUS

描述（改编自申请人摘要：金黄色葡萄球菌是一种 人类疾病的主要原因，尤其是医院感染。也是 在美国，细菌性食源性疾病的第三大常见原因 States.该微生物产生一种或多种血清学上不同的肠毒素 当在食物中生长时， 呕吐和腹泻的病理学特征， 葡萄球菌食物中毒尽管它通常与食物有关 中毒时，肠毒素也是细菌的毒力因子。的 毒素由于是超抗原，可以诱导多克隆T细胞 在受感染的个体中激活。这种激活降低了 以产生针对细菌的适当免疫反应 感染许多肠毒素的表达，就像其他 毒力相关外毒素。金黄色葡萄球菌，当被激活时， 辅助基因调节子网络（AGR）。agr系统包括两个组成部分 调节系统，作为一个群体传感器在S。金黄色。是 我认为这个系统可以使外毒素的产生最大化， 感染过程中，当主机安装炎症反应，以 感染和有机体必须作出反应，以击退吞噬细胞。 与此相一致的是，不能激活的agr突变体， 外毒素产生，比野生型亲本的毒性显著降低 株本项目利用肠毒素B和D基因作为模型系统 以确定AGR系统如何激活外毒素表达。短 来自这些肠毒素基因启动子区的DNA片段已被克隆。 位于氯霉素乙酰转移酶报告基因的前面， 已经显示含有AGR相关激活所必需的序列 的表达。在这个项目中，位点特异性突变将被引入到 负责AGR激活的序列和特定碱基将是 鉴定负责增强的调节物种的性质 表达将被识别。分子间相互作用的本质 将定义效应物种类和肠毒素基因启动子。的 RNAIII的特异性作用，即最初产生的效应物种类， 两组分系统的活化将根据以下方面进行评价： 肠毒素基因表达增强。

Description (Adapted from applicant's abstract: Staphylococcus aureus is a major cause of human disease, especially nosocomial infections. It is also the third most common cause of confirmed bacterial food borne disease in the United States. The organism produces one or more serologically distinct enterotoxins when growing in food and the ingestion of the preformed toxin is responsible for the vomiting and diarrhea symptomology which is the hallmark of staphylococcal food poisoning. Despite its usual association with food poisoning, the enterotoxins are also virulence factors for the bacterium. The toxins, by virtue of being superantigens, can elicit a polyclonal T-cell activation in an infected individual. This activation diminishes the capacity of the individual to mount an appropriate immune response against the bacterial infection. Expression of many of the enterotoxins, like that of other virulence-associated exotoxins of S. aureus, is enhanced when activated by the accessory gene regulator (agr) network. The agr system involves a two component regulatory system which functions as a quorum sensor in S. aureus. It is thought that this system maximizes exotoxin production at a time in the infectious process when the host is mounting an inflammatory-response to the infection and the organism must respond to fight off the phagocytic cells. Consistent with this are the findings that agr mutants, which cannot activate exotoxin production, are significantly less virulent than then wild-type parent strain. This project utilizes the enterotoxin B and D genes as a model system to determine how the agr system works to activate exotoxin expression. Short DNA fragments from the promoter region of these enterotoxin genes have been positioned in front of a chloramphenicol acetyltransferase reporter gene and have been shown to contain the sequences necessary for agr related activation of expression. In this project, site-specific mutations will be introduced into the sequence and the specific bases responsible for the agr activation will be identified. The nature of the regulatory species responsible for the enhanced expression will be identified. The molecular nature of the interaction between the effector species and the enterotoxin gene promoter will be defined. The specific role of RNAIII, the effector species first generated by the initial activation of the two component system, will be evaluated with regard to enhancement of enterotoxin gene expression.