Enterococci are the 3rd most common cause of community-onset infective endocarditis (IE) and the 2nd to 3rd most common cause of healthcare-associated infections overall (but are 1st-2nd in healthcare-associated IE, with E. faecalis (Efs) predominating). Antimicrobial resistance likely facilitates establishment of enterococci in the hospital setting and in the flora of hospitalized patients, and certainly makes therapy more difficult, particularly for IE. Our recent work has focused on the contributions to pathogenesis of Efs adherence to ECM proteins, a phenotype not usually seen after standard in vitro growth. We identified Ace and showed that it is an Adhesin to Collagen (CN) of Efs, that factors like serum, CN and growth at 46 C induce ace expression, that the ubiquitous ace gene is important in Efs experimental IE, that immunization with Ace protects against EIE, and we delineated the molecular mechanism of Ace's binding to CN. Our work on other Efs surface proteins which, like Ace, have deviant Ig-like folds, led us to the """"""""Ebp"""""""" genes and their role in Endocarditis, Biofilm and Pilus formation;later we showed that the ebp genes are part of the Efs core genome and are also important in ascending murine UTIs and for a second CN-adherence phenotype. We also identified a family of fibrinogen (FG)-binding MSCRAMMs that require the presence of Ebp pili to confer FG adherence to Efs cells and, recently, we showed that serum a) elicits, during growth, ECM adherence, and also b) serves as an activator of adherence, perhaps by forming bridges between ECM proteins and adhesins. In this renewal, plans for Ace are to 1) demonstrate (by introducing, into ace, the mutations that decrease in vitro CN-binding of rec-Ace) that the attenuation seen with ace knock-out mutants is specifically associated with loss of Ace's CN- binding activity (vs. an unrelated effect due to loss of this surface protein), 2) explore the efficacy of anti-Ace mAbs in preventing Efs IE and the molecular basis by which displacing mAbs function, and 3) determine the mechanism of ace induction by serum and CN. Goals relating to Ebp pili and FG adhesins are to 1) localize Ebp pilin subunits within pili and define the role of these subunits and two sortases in pilus biogenesis, 2) identify the mechanism responsible for pilus-associated (non-Ace) CN adherence and the role of individual pilins in biofilm, cell adherence, and virulence, 3) determine the basis for elimination of FG adherence in pilus mutants even though FG-adhesins are still present, 4) determine if immunity against Ebp subunits prevents experimental IE, and 5) investigate the mechanism by which serum elicits pilus formation and conditions and mechanisms for pilus regulation. Finally, we will investigate a possible additive effect between ace and ebpABC in EIE and between mAbs to them in inhibition of CN adherence of Efs cells. Our long-range goals are 1) to understand the mechanism of action of these adhesins in pathogenesis, with 2) the hope that the results of our studies will form the basis for rational design of modalities to prevent or ameliorate Efs infections, and 3) will provide a better understanding of how this organism interacts with the human host.

Public Health Relevance

This proposal seeks to understand how enterococci, bacteria that are important in hospital-associated infections, cause heart valve infections, a uniformly fatal disease without antibiotics. We seek to understand how these bacteria attach to heart valves and other human tissues and proteins, and to develop ways to prevent these infections.

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 Texas Health Science Center Houston
Internal Medicine/Medicine
Schools of Medicine
United States
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Gao, Peng; Pinkston, Kenneth L; Bourgogne, Agathe et al. (2017) Functional studies of E. faecalis RNase J2 and its role in virulence and fitness. PLoS One 12:e0175212
Singh, Kavindra V; Tran, Truc T; Nannini, Esteban C et al. (2017) Efficacy of Ceftaroline against Methicillin-Susceptible Staphylococcus aureus Exhibiting the Cefazolin High-Inoculum Effect in a Rat Model of Endocarditis. Antimicrob Agents Chemother 61:
La Rosa, Sabina Leanti; Montealegre, Maria Camila; Singh, Kavindra V et al. (2016) Enterococcus faecalis Ebp pili are important for cell-cell aggregation and intraspecies gene transfer. Microbiology 162:798-802
Montealegre, Maria Camila; Singh, Kavindra V; Somarajan, Sudha R et al. (2016) Role of the Emp Pilus Subunits of Enterococcus faecium in Biofilm Formation, Adherence to Host Extracellular Matrix Components, and Experimental Infection. Infect Immun 84:1491-1500
Singh, Kavindra V; La Rosa, Sabina Leanti; Somarajan, Sudha R et al. (2015) The fibronectin-binding protein EfbA contributes to pathogenesis and protects against infective endocarditis caused by Enterococcus faecalis. Infect Immun 83:4487-94
Panesso, Diana; Planet, Paul J; Diaz, Lorena et al. (2015) Methicillin-Susceptible, Vancomycin-Resistant Staphylococcus aureus, Brazil. Emerg Infect Dis 21:1844-8
Montealegre, Maria Camila; La Rosa, Sabina Leanti; Roh, Jung Hyeob et al. (2015) The Enterococcus faecalis EbpA Pilus Protein: Attenuation of Expression, Biofilm Formation, and Adherence to Fibrinogen Start with the Rare Initiation Codon ATT. MBio 6:e00467-15
Tran, Truc T; Palmer, Hannah R; Weimar, Marion R et al. (2015) Oral Bacitracin: A Consideration for Suppression of Intestinal Vancomycin-Resistant Enterococci (VRE) and for VRE Bacteremia From an Apparent Gastrointestinal Tract Source. Clin Infect Dis 60:1726-8
Somarajan, Sudha R; La Rosa, Sabina Leanti; Singh, Kavindra V et al. (2015) The fibronectin-binding protein Fnm contributes to adherence to extracellular matrix components and virulence of Enterococcus faecium. Infect Immun 83:4653-61
Roh, Jung Hyeob; Singh, Kavindra V; La Rosa, Sabina Leanti et al. (2015) The two-component system GrvRS (EtaRS) regulates ace expression in Enterococcus faecalis OG1RF. Infect Immun 83:389-95

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