Biofilms and Enterococcus faecalis Biology

描述（由申请人提供）：粪肠球菌是从医院相关感染患者中分离出的前三种最常见的细菌之一，它可以引起高度致命的心内膜炎。肠球菌对抗菌剂具有高度的固有和获得性耐药性，而且它们倾向于作为耐药性基因向更高致病性生物体传播的主要渠道，这增强了肠球菌的医学重要性。肠球菌通常从植入医疗器械上形成的生物膜中分离出来，在心脏瓣膜上定植和生长也被认为是生物膜生长的一种形式。生物膜环境可能是肠球菌向金黄色葡萄球菌转移高水平万古霉素耐药性的生态位。我们已经使用遗传筛选来鉴定大量体外生物膜形成的新遗传决定因素，并且正在进行的研究为许多这些决定因素在体内感染期间形成的生物膜中的重要性提供了越来越多的证据。许多以前未被表征的肠球菌生物膜决定因子在多种重要病原体中显示出显著的保守性；如果它们在功能上是保守的，这些基因的产物就构成了开发化学抑制剂或疫苗的潜在靶标库，这些化学抑制剂或疫苗可以在许多不同病原体产生的感染期间阻止生物膜的形成。当前资助的结果为回答肠球菌生物膜形成的重要基本问题提供了坚实的基础，也为增加我们对细菌致病机制的理解提供了新方法。为解决这些问题而提出的具体目标是：利用本基金提供的信息和资源，确定以下过程中涉及的关键信号和调节机制：a)从浮游生物到生物膜生长的初始过渡；b)生物膜群落的后续发展。2. 确定肠球菌生物膜形成相关基因的破坏对毒力的影响，并从粪肠球菌中发现的新型生物膜决定因素中鉴定金黄色葡萄球菌功能保守的生物膜/毒力基因。3. 确定粪肠杆菌核心基因组中生物膜诱导的抗生素耐药性决定因素。

DESCRIPTION (provided by applicant): Enterococcus faecalis iis one of the top three most frequently-isolated species from hospital- associated infections of 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 and acquired resistance to antimicrobial agents, and by their propensity to act as a major conduit for the spread of resistance genes to more highly-pathogenic organisms. Enterococci are commonly isolated from biofilms formed on implanted medical devices, and colonization and growth on heart valves is also considered a form of biofilm growth. The biofilm environment is a likely niche for transfer of high-level vancomycin resistance from enterococci to Staphylococcus aureus. We have used genetic screens to identify a large number of novel genetic determinants of biofilm formation in vitro, and ongoing studies provide increasing evidence for the importance of many of these determinants in biofilms formed in vivo during infections. Many previously un-characterized enterococcal biofim determinants show significant conservation in a variety of important pathogens; if they are functionally conserved, the products of these genes comprise a pool of potential targets for the development of chemical inhibitors or vaccines that could block biofilm formation during infections produced by many different pathogens . The results from the current grant provide a strong foundation for answering important basic questions about the biology of enterococcal biofilm formation, as well as new approaches to increasing our understanding of bacterial pathogenic mechanisms. The specific aims proposed to address these questions are to: 1. Use the information and resources from the present grant to identify critical signals and regulatory mechanisms involved in: a) the initial transition from planktonic to biofilm growth and, b) the subsequent development of the biofilm community. 2. Determine the effects of disruption of genes involved in enterococcal biofilm formation on virulence and identify functionally-conserved biofilm/virulence genes in S. aureus from the pool of novel biofilm determinants discovered in E. faecalis. 3. Identify determinants of biofilm-induced antibiotic resistance in the core genome of E. faecalis. PUBLIC HEALTH RELEVANCE: The research proposed in this application is focused on the process by which a bacterium called Enterococcus faecalis is able to grow on surfaces in a structure called a biofilm. In recent years it has become widely accepted that bacterial growth in biofilms causes major differences in the physiology and behavior of bacteria from that observed in liquid cultures, and that biofilm formation is involved in the production of many, if not most bacterial infections. Our research will employing genetic techniques to identify and characterize previously un-studied enterococcal genes that are important in biofilm formation, and to determine whether similar genes in another important pathogen, Staphylococcus aureus, have the same biological functions as the enterococcal genes. If there is functional conservation of these genes, it could speed the development of new antimicrobial drugs or vaccines.