In vitro testing of daptomycin plus rifampin against methicillin-resistant Staphylococcus aureus resistant to rifampin

Saudi Med J. 2008 Dec;29(12):1726-9.


Objective: To test for synergy between daptomycin (DAP) and rifampin (RIF) against RIF-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolates.

Methods: Synergy testing using time-kill assay (TKA) was performed on 6 clinically, and genetically unique RIF-resistant MRSA isolates. The isolates were identified out of 489 (1.2%) samples collected during April 2003 to August 2006, from patients at the Ochsner Medical Center in New Orleans, Louisiana, United States of America.

Results: Synergy testing of DAP plus RIF by TKA showed that 5 isolates were indifferent, but one isolate was antagonistic.

Conclusion: Our in vitro study failed to demonstrate synergy between DAP plus RIF, against our RIF-resistant MRSA isolates. Clinical failure of this combination should prompt the clinician to consider antagonism, as one of the potential causes.

MeSH terms

  • Anti-Bacterial Agents / administration & dosage*
  • Daptomycin / administration & dosage*
  • Drug Therapy, Combination
  • Humans
  • Methicillin-Resistant Staphylococcus aureus*
  • Rifampin / administration & dosage*
  • Staphylococcal Infections / drug therapy*


  • Anti-Bacterial Agents
  • Daptomycin
  • Rifampin