Ticarcillin-tobramycin-rifampin: in vitro synergy of the triplet combination against Pseudomonas aeruginosa

J Lab Clin Med. 1983 Jun;101(6):896-902.


MICs of ticarcillin, tobramycin, and rifampin alone and in combination were determined by a three-dimensional checkerboard method for 33 isolates of Pseudomonas aeruginosa. Twenty-nine of 33 isolates were affected synergistically (FIC index less than 1.0) by the combination of ticarcillin-tobramycin, including 13 of the 16 isolates resistant to ticarcillin and/or tobramycin alone. However, despite fulfilling the criteria for synergy, the MIC of the ticarcillin and/or tobramycin when in combination still exceeded attainable serum concentrations for 12 of the 13 resistant isolates. When rifampin was added to ticarcillin-tobramycin, a synergistic interaction was observed for all 33 isolates. Furthermore, of the 16 isolates resistant to ticarcillin and/or tobramycin, eight were inhibited by attainable concentrations of all three antibiotics in combination. If these results can be confirmed in the clinical situation, application of the three-drug combination of ticarcillin-tobramycin-rifampin might improve survival in selected patients with serious P. aeruginosa infections.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Drug Combinations
  • Drug Synergism
  • Microbial Sensitivity Tests
  • Penicillins / pharmacology*
  • Pseudomonas aeruginosa / drug effects*
  • Rifampin / pharmacology*
  • Ticarcillin / pharmacology*
  • Tobramycin / pharmacology*


  • Anti-Bacterial Agents
  • Drug Combinations
  • Penicillins
  • Ticarcillin
  • Rifampin
  • Tobramycin