TICARCILLIN-TOBRAMYCIN-RIFAMPIN - INVITRO SYNERGY OF THE TRIPLET COMBINATION AGAINST PSEUDOMONAS-AERUGINOSA

  • 1 January 1983
    • journal article
    • research article
    • Vol. 101  (6) , 896-902
Abstract
MIC [median inhibitory concentration] of ticarcillin, tobramycin and rifampin alone and in combination were determined by a 3-dimensional checkerboard method for 33 isolates of P. aeruginosa. Of 33 isolates, 29 were affected synergistically (FIC [fractional inhibitory concentration] index < 1.0) by the combination of ticarcillin-tobramycin, including 13 of the 16 isolates resistant to ticarcillin and/or tobramycin alone. 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. Of the 16 isolates resistant to ticarcillin and/or tobramycin, 8 were inhibited by attainable concentrations of all 3 antibiotics in combination. If these results can be confirmed in the clinical situation, application of the 3-drug combination of ticarcillin-tobramycin-rifampin might improve survival in selected patients with serious P. aeruginosa infections.