title: Daptomycin-β-Lactam Combinations in a Rabbit Model of Daptomycin-Nonsusceptible Methicillin-Resistant Staphylococcus aureus Endocarditis.
abstract: Beta-lactams enhance the in vitro activity of daptomycin against methicillin-resistant strains of Staphylococcus aureus Experiments were performed in a rabbit model of aortic valve endocarditis caused by methicillin-resistant daptomycin-nonsusceptible S. aureus strain CB5054 to determine if a cephalosporin, ceftriaxone, administered as a once-daily dose of 100 mg/kg of body weight, or a carbapenem, ertapenem, administered as a once-daily dose of 40 mg/kg, improved the efficacy of daptomycin, administered as a once-daily dose of 12 mg/kg. Daptomycin was ineffective alone in reducing organism densities compared to untreated controls in vegetations and spleen, but densities were 1.4 log10 CFU/g lower in kidney. The combination of daptomycin plus ceftriaxone or daptomycin plus ertapenem reduced bacterial densities in all tissues compared to single agents, with 0.6 to 1.0 log10 CFU/g fewer organisms in vegetations, 1.5 to 2.5 log10 CFU/g fewer organisms in spleen, and 1.8 to 2.5 log10 CFU/g fewer organisms in kidney, although differences were statistically significant only in spleen for daptomycin plus ceftriaxone and in kidney for daptomycin plus ertapenem. Drug exposures in rabbits were less than those achievable in humans, which may have limited the in vivo activity, particularly in vegetations.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, San Francisco General Hospital, University of California, San Francisco, San Francisco, California, USA henry.chambers@ucsf.edu.
authors.forename: Henry F
authors.initials: HF
authors.lastname: Chambers
authors.affiliation: Division of Infectious Diseases, Department of Medicine, San Francisco General Hospital, University of California, San Francisco, San Francisco, California, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Basuino
authors.affiliation: Division of Infectious Diseases, Department of Medicine, San Francisco General Hospital, University of California, San Francisco, San Francisco, California, USA.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Hamilton
authors.affiliation: Division of Infectious Diseases, Department of Medicine, San Francisco General Hospital, University of California, San Francisco, San Francisco, California, USA Division of Infectious Diseases, Soonchunhyang University Hospital, Seoul, Republic of Korea.
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Choo
authors.affiliation: Merck & Co., Inc., Kenilworth, New Jersey, USA.
authors.forename: Pamela
authors.initials: P
authors.lastname: Moise
mesh_terms: D000818:Animals; D002443:Ceftriaxone / Q000627:therapeutic use; D002511:Cephalosporins / Q000627:therapeutic use; D017576:Daptomycin / Q000627:therapeutic use*; D004697:Endocarditis, Bacterial / Q000188:drug therapy* / Q000382:microbiology*; D000077727:Ertapenem; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000472:pathogenicity*; D008826:Microbial Sensitivity Tests; D011817:Rabbits; D047090:beta-Lactams / Q000627:therapeutic use*
chemical_list: D002511:Cephalosporins; D047090:beta-Lactams; D002443:Ceftriaxone; D000077727:Ertapenem; D017576:Daptomycin