GENETICS OF CAPSULAR POLYSACCHARIDE PRODUCTION IN ENTEROCOCCUS FAECALIS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。肠球菌是医院获得性感染的主要原因，占所有医院感染的近10%。肠球菌引起的感染由于存在多重耐药，构成了重大的治疗挑战。拟议的研究将确定如何在遗传水平上实现胶囊多样性。最近的证据表明，粪肠球菌具有数量有限的荚膜血清型，大多数分离株属于4种主要血清型（a - d）。最近的临床证据表明，具有C和D胶囊型的粪肠球菌菌株可能比表达其他胶囊型的菌株更具致病性。基于广泛的免疫交叉反应，血清型C和D似乎在结构上相关。血清型C胶囊生物合成的遗传基础是由一个由9个基因组成的操纵子编码，命名为cpsC-K。血清C和D菌株的遗传比较发现，除cpsF外，操纵子中每个基因的序列都有广泛的保守性，cpsF仅存在于血清C菌株中。我们的目标是通过在粪肠杆菌V583（一种血清型C菌株）中构建cpsF的框架内缺失突变体来解决这一差异。D型菌株与天然胶囊启动子表达的cpsF在多拷贝质粒上的互补也将用于证实cpsF的存在赋予C型特异性的假设。这些衍生的菌株将使用类型特异性抗血清进行ELISA检测。此外，将对纯化的荚膜材料进行GC/MS碳水化合物组成分析，以确定C型和D型血清型差异的组成基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Entercocci are leading causes of hospital-acquired infections, accounting for nearly 10% of all nosocomial infections. Infections caused by enterococci constitute a significant treatment challenge due to the presence of multi-drug resistance. The proposed studies will determine how capsule diversity is achieved at the genetic level. Recent evidence suggests that E. faecalis has a limited number of capsular serotypes and that the majority of isolates fall into 4 predominant serotypes (A-D). Recent clinical evidence suggests that E. faecalis strains possessing capsule types C and D maybe more pathogenic than strains expressing other capsule types. Serotypes C and D appear to be structurally related based on extensive immunologic cross-reactivity. The genetic basis for serotype C capsule biosynthesis is encoded by an operon of 9 genes, designated cpsC-K. Genetic comparison between serogroup C and D strains revealed extensive sequence conservation for each gene in the operon with the exception of cpsF, which was only present in serotype C strains. We aim to address this difference by constructing an in-frame deletion mutant of cpsF in E. faecalis V583, a serotype C strain. Complementation of type D strains with cpsF expressed from the native capsule promoter on a multi-copy plasmid will also be used to confirm the hypothesis that the presence of cpsF confers type C specificity. These derived strains will be examined by ELISA using type-specific antisera. In addition, carbohydrate compositional analysis on purified capsular material using GC/MS will be performed to determine the compositional basis for the serotype differences between types C and D.