Efficacy of usual and high doses of daptomycin in combination with rifampin versus alternative therapies in experimental foreign-body infection by methicillin-resistant Staphylococcus aureus

Antimicrob Agents Chemother. 2010 Dec;54(12):5251-6. doi: 10.1128/AAC.00226-10. Epub 2010 Oct 4.

Abstract

The treatment of prosthetic joint infections caused by methicillin-resistant Staphylococcus aureus (MRSA) continues to be a challenge for the clinician. The aim of this study was to evaluate the efficacies of daptomycin at usual and high doses (equivalent to 6 and 10 mg/kg of body weight/day, respectively, in humans) and in combination with rifampin and to compare the activities to those of conventional anti-MRSA therapies. We used MRSA strain HUSA 304, with the following MICs and minimal bactericidal concentrations (MBCs), respectively: daptomycin, 1 μg/ml and 4 μg/ml; vancomycin, 2 μg/ml and 4 μg/ml; linezolid, 2 μg/ml and >32 μg/ml; and rifampin, 0.03 μg/ml and 0.5 μg/ml. In time-kill curves, only daptomycin and its combinations with rifampin achieved a bactericidal effect in log and stationary phases. For in vivo studies, we used a rat foreign-body infection model. Therapy was administered for 7 days with daptomycin at 100 mg/kg/day and 45/mg/kg/day, vancomycin at 50 mg/kg/12 h, rifampin at 25 mg/kg/12 h, and linezolid at 35 mg/kg/12 h, and each antibiotic was also combined with rifampin. Among monotherapies, daptomycin at 100 mg/kg/day and rifampin performed better than vancomycin and linezolid. In combination with rifampin, both dosages of daptomycin were significantly better than all other combinations, but daptomycin at 100 mg/kg/day plus rifampin achieved better cure rates at day 11 (P < 0.05) than daptomycin at 45 mg/kg/day plus rifampin. Resistant strains were found in monotherapies with rifampin and daptomycin at 45 mg/kg/day. In conclusion, daptomycin at high doses was the most effective monotherapy and also improved the efficacy of the combination with rifampin against foreign-body infections by MRSA. Clinical studies should confirm whether this combination may be considered the first-line treatment for foreign-body infections by MRSA in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / administration & dosage
  • Acetamides / pharmacology
  • Animals
  • Anti-Bacterial Agents* / administration & dosage
  • Anti-Bacterial Agents* / pharmacology
  • Anti-Infective Agents
  • Daptomycin / administration & dosage*
  • Daptomycin / pharmacology*
  • Linezolid
  • Male
  • Methicillin-Resistant Staphylococcus aureus / drug effects*
  • Microbial Sensitivity Tests
  • Oxazolidinones / administration & dosage
  • Oxazolidinones / pharmacology
  • Rats
  • Rats, Wistar
  • Rifampin / administration & dosage*
  • Rifampin / pharmacology*
  • Staphylococcal Infections / drug therapy*
  • Vancomycin / administration & dosage
  • Vancomycin / pharmacology

Substances

  • Acetamides
  • Anti-Bacterial Agents
  • Anti-Infective Agents
  • Oxazolidinones
  • Vancomycin
  • Linezolid
  • Daptomycin
  • Rifampin