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N Engl J Med. Genetic Basis for In Vivo Daptomycin Resistance in Enterococci

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  • N Engl J Med. Genetic Basis for In Vivo Daptomycin Resistance in Enterococci

    [Source: The New England Journal of Medicine, full text: (LINK). Abstract, edited.]

    Original Article
    Genetic Basis for In Vivo Daptomycin Resistance in Enterococci



    Cesar A. Arias, M.D., Ph.D., Diana Panesso, Ph.D., Danielle M. McGrath, Ph.D., Xiang Qin, Ph.D., Maria F. Mojica, M.Sc., Corwin Miller, B.A., Lorena Diaz, B.Sc., Truc T. Tran, Pharm.D., Sandra Rincon, M.Sc., E. Magda Barbu, Ph.D., Jinnethe Reyes, M.Sc., Jung H. Roh, Ph.D., Elizabeth Lobos, Ph.D., Erica Sodergren, Ph.D., Renata Pasqualini, Ph.D., Wadih Arap, M.D., Ph.D., John P. Quinn, M.D., Yousif Shamoo, Ph.D., Barbara E. Murray, M.D., and George M. Weinstock, Ph.D.

    N Engl J Med 2011; 365:892-900 - September 8, 2011


    Background

    Daptomycin is a lipopeptide with bactericidal activity that acts on the cell membrane of enterococci and is often used off-label to treat patients infected with vancomycin-resistant enterococci. However, the emergence of resistance to daptomycin during therapy threatens its usefulness.


    Methods

    We performed whole-genome sequencing and characterization of the cell envelope of a clinical pair of vancomycin-resistant Enterococcus faecalis isolates from the blood of a patient with fatal bacteremia; one isolate (S613) was from blood drawn before treatment and the other isolate (R712) was from blood drawn after treatment with daptomycin. The minimal inhibitory concentrations (MICs) of these two isolates were 1 and 12 μg per milliliter, respectively. Gene replacements were made to exchange the alleles found in isolate S613 with those in isolate R712.


    Results

    Isolate R712 had in-frame deletions in three genes. Two genes encoded putative enzymes involved in phospholipid metabolism, GdpD (which denotes glycerophosphoryl diester phosphodiesterase) and Cls (which denotes cardiolipin synthetase), and one gene encoded a putative membrane protein, LiaF (which denotes lipid II cycle-interfering antibiotics protein but whose exact function is not known). LiaF is predicted to be a member of a three-component regulatory system (LiaFSR) involved in the stress-sensing response of the cell envelope to antibiotics. Replacement of the liaF allele of isolate S613 with the liaF allele from isolate R712 quadrupled the MIC of daptomycin, whereas replacement of the gdpD allele had no effect on MIC. Replacement of both the liaF and gdpD alleles of isolate S613 with the liaF and gdpD alleles of isolate R712 raised the daptomycin MIC for isolate S613 to 12 μg per milliliter. As compared with isolate S613, isolate R712 ? the daptomycin-resistant isolate ? had changes in the structure of the cell envelope and alterations in membrane permeability and membrane potential.


    Conclusions

    Mutations in genes encoding LiaF and a GdpD-family protein were necessary and sufficient for the development of resistance to daptomycin during the treatment of vancomycin-resistant enterococci. (Funded by the National Institute of Allergy and Infectious Diseases and the National Institutes of Health.)


    Supported by grants from the National Institute of Allergy and Infectious Diseases (Pathway to Independence Award R00 AI72961, to Dr. Arias; R01 AI067861 and R37 AI47923, to Dr. Murray; and R01 AI080714, to Dr. Shamoo) and a grant for genome sequencing from the National Institutes of Health (1U54 HG004968, to Dr. Weinstock).

    Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.

    Drs. Panesso and McGrath contributed equally to this article.
    We thank Silvia Munoz-Price, James H. Jorgensen, Helio Sader, Ronald Jones, Chris Pillar, and Daniel Sahm for providing the enterococcal isolates; Arnold S. Bayer, Jared Silverman, and Pablo Okhuysen for useful discussions; and Kevin Morano, I-Hsiu Huang, and **** Ton-That for technical assistance with the cell-membrane and electron-microscopy experiments.


    Source Information

    From the Department of Internal Medicine, Division of Infectious Diseases (C.A.A., D.P., M.F.M., L.D., T.T.T., J.H.R., B.E.M.), and the Department of Microbiology and Molecular Genetics (B.E.M.), University of Texas Medical School at Houston; the David H. Koch Center, University of Texas M.D. Anderson Cancer Center (D.M.M., E.M.B., R.P., W.A.); the Human Genome Center, Baylor College of Medicine (X.Q.); the Institute of Biosciences and Bioengineering, Rice University (C.M., Y.S.); and the University of Houston College of Pharmacy (T.T.T.) ? all in Houston; the Molecular Genetics and Antimicrobial Resistance Unit, Universidad El Bosque, Bogota (C.A.A., D.P., L.D., S.R., J.R.); and the Center for Medical Research and Training, Cali (M.F.M.) ? both in Colombia; Washington University at St. Louis, St. Louis (E.L., E.S., G.M.W.); the Chicago Infectious Disease Institute, Chicago (J.P.Q.); and Pfizer Worldwide Research and Development, Groton, CT (J.P.Q.).
    Address reprint requests to Dr. Arias at the University of Texas Medical School, 6431 Fannin St., Rm. MSB 2.112, Houston, TX 77030, or at cesar.arias@uth.tmc.edu.
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