Biofilms and Enterococcus faecalis Biology

描述(申请人提供)：粪肠球菌是哺乳动物肠道中的一种正常寄居者，在健康人类中通常不具有致病性。然而，它已经成为妥协患者的主要医院病原体，并可导致一种高度致命的心内膜炎。肠球菌对抗菌剂具有高度的内在抗药性，并倾向于通过水平转移获得和捐献新的耐药基因，从而增强了肠球菌的医学重要性。肠球菌通常是从植入的医疗设备如导管和喂养管上形成的生物膜中分离出来的，在心脏瓣膜上的定植和生长可能代表了生物膜生长状态的一种形式。最近的一份报告表明，生物被膜环境可能是将高水平的万古霉素耐药性从肠球菌转移到金黄色葡萄球菌的利基环境。在这个项目中，将使用体外和动物模型来分析粪肠球菌生物膜形成的生理学和遗传学。这项工作可能导致鉴定使生物体从共生生活方式适应病原体生活方式所需的新基因产物。该项目的具体目标是： 1)鉴定形成生物膜所需的粪肠球菌遗传决定因素。 2)利用报告基因结构来监测生物膜中的表达，并表征粪肠球菌为适应浮游生物膜生长所使用的传感机制。 3)用高分辨扫描电子显微镜分析粪肠球菌生物膜的细胞和分子结构。 4)检测筛选出的生物膜缺陷突变株对实验性心内膜炎的毒力。

DESCRIPTION (provided by applicant): Enterococcus faecalis is a normal inhabitant of the mammalian intestinal tract, and is not normally pathogenic in healthy humans. However, it has become a major nosocomial pathogen in compromised patients and it can cause a highly fatal form of endocarditis. The medical importance of the enterococci is enhanced by their high degree of inherent resistance to antimicrobial agents, and their propensity to both acquire and to donate novel resistance genes by horizontal transfer. Enterococci are commonly isolated from biofilms formed on implanted medical devices such as catheters and feeding tubes, and colonization and growth on heart valves may represent a form of the biofilm growth state. A recent report suggests the biofilm environment as a likely niche for transfer of high-level vancomycin resistance from enterococci to Staphylococcus aureus. In this project, the physiology and genetics of biofilm formation in E. faecalis will be analyzed using both in vitro and animal models. This work could lead to the identification of novel gene products required for the adaptation of the organisms from a commensal lifestyle to that of a pathogen. The specific aims of the project are: 1) To identify the E. faecalis genetic determinants required for biofilm formation. 2) To use reporter gene constructs to monitor expression in biofilms, and to characterize the sensing machinery used by E. faecalis to adapt to biofilm growth from planktonic growth. 3) To analyze the cellular and molecular structure of E. faecalis biofilms using high resolution scanning electron microscopy. 4) To test the virulence of selected biofilm-deficient mutants in experimental endocarditis.