This proposal presents a five-year research career development program focused on the study of the mechanism of resistance of Enterococcus faecium to the lipopeptide antibiotic daptomycin. E. faecium is known as one of the """"""""no-ESKAPE"""""""" pathogens and has become one of the most challenging organisms to treat successfully in the clinical setting due to its multi-drug resistant nature, increasing prevalence, high attributable costs and limited antibiotics with reliable activity against this organism. Daptomycin is a lipopeptide antibiotic which has become the last-resort drug for the treatment of enterococcal infections due to is potent in vitro activity. However, with increasing use, the emergence of daptomycin-resistant Enterococcus is on the rise. Previous whole genome sequence comparison of a clinical strain-pair of E. faecium identified mutation in the histidine kinase of a two-component regulatory system designated YycFG, which is an essential two-component regulatory system involved in the cell envelope response to antibiotics. The role of YycFG in the development of daptomycin resistance in enterococci has not been characterized. The current proposal aims to uncover the role of the YycFG regulon in development of daptomycin resistance and design new pharmacological strategies to optimize the use of daptomycin in E. faecium isolates with alterations in the YycFG system. The following specific aims are outlined in this proposal:
Specific Aim I : Characterization of the YycFG cell envelope regulon in E. faecium and Specific Aim II: Evaluation of pharmacologic strategies to treat daptomycin-resistant E. faecium. Successful completion of this work will provide insights into the genetic dynamics of resistance and cell-wall homeostasis of E. faecium and is likely to provide novel targets that could be explored therapeutically to overcome the rise of daptomycin resistance with the ultimate goal of helping clinicians improve treatment of patients infected with multidrug-resistant bacteria. Additionally, this project will serve as a platform to support the transition of a young clinician-researcher to independence whose expertise will combine bacterial molecular genetics and antimicrobial pharmacology.

Public Health Relevance

Antibiotic resistance is an important public health threat that is highlighted by the Word Health Organization and the Centers for Disease Control as a matter of top priority. Antibiotic-resistant bacteria are becoming more prevalent, can quickly spread in the hospital and in the community and have become more difficult to cure and expensive to treat. This proposal focuses on Enterococcus faecium, a multidrug-resistant organism that usually affect debilitated patients and that has been highlighted by the Infectious Disease of America as one of the bacteria against which new therapies are urgently needed. This project seeks to investigate the molecular basis of resistance to daptomycin, one of the last-resort antibiotics, with the objective of optimizing the use of this drug against these bacteria and identify new targets for antibiotic development.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Clinical Investigator Award (CIA) (K08)
Project #
Application #
Study Section
Microbiology and Infectious Diseases Research Committee (MID)
Program Officer
Huntley, Clayton C
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Texas Health Science Center Houston
Internal Medicine/Medicine
Schools of Medicine
United States
Zip Code
Kebriaei, Razieh; Rice, Seth A; Singh, Kavindra V et al. (2018) Influence of Inoculum Effect on the Efficacy of Daptomycin Monotherapy and in Combination with ?-Lactams against Daptomycin-Susceptible Enterococcus faecium Harboring LiaSR Substitutions. Antimicrob Agents Chemother 62:
Tran, Truc T; Tam, Vincent H; Murray, Barbara E et al. (2017) Efficacy of Telavancin Alone and in Combination with Ampicillin in a Rat Model of Enterococcus faecalis Endocarditis. Antimicrob Agents Chemother 61:
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:
Mishra, Nagendra N; Tran, Truc T; Seepersaud, Ravin et al. (2017) Perturbations of Phosphatidate Cytidylyltransferase (CdsA) Mediate Daptomycin Resistance in Streptococcus mitis/oralis by a Novel Mechanism. Antimicrob Agents Chemother 61:
Nigo, Masayuki; Diaz, Lorena; Carvajal, Lina P et al. (2017) Ceftaroline-Resistant, Daptomycin-Tolerant, and Heterogeneous Vancomycin-Intermediate Methicillin-Resistant Staphylococcus aureus Causing Infective Endocarditis. Antimicrob Agents Chemother 61:
Yim, Juwon; Smith, Jordan R; Singh, Nivedita B et al. (2017) Evaluation of daptomycin combinations with cephalosporins or gentamicin against Streptococcus mitis group strains in an in vitro model of simulated endocardial vegetations (SEVs). J Antimicrob Chemother 72:2290-2296
DiPippo, Adam J; Tverdek, Frank P; Tarrand, Jeffrey J et al. (2017) Daptomycin non-susceptible Enterococcus faecium in leukemia patients: Role of prior daptomycin exposure. J Infect 74:243-247
Munita, Jose M; Aitken, Samuel L; Miller, William R et al. (2017) Multicenter Evaluation of Ceftolozane/Tazobactam for Serious Infections Caused by Carbapenem-Resistant Pseudomonas aeruginosa. Clin Infect Dis 65:158-161
Tran, Truc T; Miller, William R; Shamoo, Yousif et al. (2016) Targeting cell membrane adaptation as a novel antimicrobial strategy. Curr Opin Microbiol 33:91-96
Shukla, Bhavarth S; Shelburne, Samuel; Reyes, Katherine et al. (2016) Influence of Minimum Inhibitory Concentration in Clinical Outcomes of Enterococcus faecium Bacteremia Treated With Daptomycin: Is it Time to Change the Breakpoint? Clin Infect Dis 62:1514-1520

Showing the most recent 10 out of 17 publications