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.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Bacterial Pathogenesis Study Section (BACP)
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Huntley, Clayton C
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University of Minnesota Twin Cities
Schools of Medicine
United States
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Dale, Jennifer L; Nilson, Jennifer L; Barnes, Aaron M T et al. (2017) Restructuring of Enterococcus faecalis biofilm architecture in response to antibiotic-induced stress. NPJ Biofilms Microbiomes 3:15
Frank, Kristi L; Vergidis, Paschalis; Brinkman, Cassandra L et al. (2015) Evaluation of the Enterococcus faecalis Biofilm-Associated Virulence Factors AhrC and Eep in Rat Foreign Body Osteomyelitis and In Vitro Biofilm-Associated Antimicrobial Resistance. PLoS One 10:e0130187
Dale, Jennifer L; Cagnazzo, Julian; Phan, Chi Q et al. (2015) Multiple roles for Enterococcus faecalis glycosyltransferases in biofilm-associated antibiotic resistance, cell envelope integrity, and conjugative transfer. Antimicrob Agents Chemother 59:4094-105
Cook, Laura C C; Dunny, Gary M (2014) The Influence of Biofilms in the Biology of Plasmids. Microbiol Spectr 2:
Frank, Kristi L; Colomer-Winter, Cristina; Grindle, Suzanne M et al. (2014) Transcriptome analysis of Enterococcus faecalis during mammalian infection shows cells undergo adaptation and exist in a stringent response state. PLoS One 9:e115839
Cook, Laura C C; Dunny, Gary M (2014) The influence of biofilms in the biology of plasmids. Microbiol Spectr 2:0012
Leuck, Anne-Marie; Johnson, James R; Dunny, Gary M (2014) A widely used in vitro biofilm assay has questionable clinical significance for enterococcal endocarditis. PLoS One 9:e107282
Frank, Kristi L; Guiton, Pascale S; Barnes, Aaron M T et al. (2013) AhrC and Eep are biofilm infection-associated virulence factors in Enterococcus faecalis. Infect Immun 81:1696-708
Dunny, Gary M (2013) Enterococcal sex pheromones: signaling, social behavior, and evolution. Annu Rev Genet 47:457-82
Cook, L C; Dunny, G M (2013) Effects of biofilm growth on plasmid copy number and expression of antibiotic resistance genes in Enterococcus faecalis. Antimicrob Agents Chemother 57:1850-6

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