Biofilms and Enterococcus faecalis Biology

描述(由申请人提供)：粪肠球菌i型是最常见的三种分离菌株之一，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和获得性耐药性，并倾向于充当耐药性基因向更高致病性生物传播的主要渠道，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也被认为是生物膜生长的一种形式。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。我们已经使用遗传筛选来确定大量新的体外生物膜形成的遗传决定因素，正在进行的研究提供了越来越多的证据，证明这些决定因素中的许多在感染期间在体内形成的生物膜中的重要性。许多以前没有特征化的肠球菌生物膜决定簇在各种重要病原体中显示出显著的保守性；如果它们在功能上保守，这些基因的产物就构成了一个潜在靶点，用于开发化学抑制剂或疫苗，这些药物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。目前的资助结果为回答有关肠球菌生物被膜形成的生物学的重要基本问题以及增加我们对细菌致病机制的理解提供了坚实的基础。提出的解决这些问题的具体目标是：1.利用目前赠款的信息和资源，确定涉及以下方面的关键信号和调控机制：a)从浮游到生物膜生长的初始过渡，以及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中断对毒力的影响，并从粪肠球菌中发现的新的生物膜决定因素库中鉴定功能保守的金黄色葡萄球菌生物膜/毒力基因。3.确定粪肠球菌核心基因组中生物膜诱导的抗生素耐药性的决定因素。 公共卫生相关性：本申请中提出的研究重点是一种名为粪肠球菌的细菌能够在一种名为生物膜的结构的表面上生长的过程。近年来，人们普遍认为，细菌在生物膜中的生长会导致细菌的生理和行为与液体培养中观察到的细菌有很大的不同，生物膜的形成参与了许多细菌感染的产生，如果不是大多数细菌感染的话。我们的研究将利用基因技术来鉴定和鉴定以前未被研究过的在生物被膜形成中起重要作用的肠球菌基因，并确定另一种重要病原体金黄色葡萄球菌中的类似基因是否具有与肠球菌基因相同的生物学功能。如果这些基因的功能得到保护，可能会加快新的抗菌药物或疫苗的开发。

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.