PSEUDOMONAS-AERUGINOSA BACTEREMIA - SUSCEPTIBILITY OF 100 BLOOD CULTURE ISOLATES TO 7 ANTI-MICROBIAL AGENTS AND ITS CLINICAL SIGNIFICANCE

  • 1 January 1979
    • journal article
    • research article
    • Vol. 94  (2) , 201-214
Abstract
The susceptibility of 100 blood culture isolates of P. aeruginosa observed during 4 1/2 yr was tested for tobramycin, netilmicin, gentamicin, amikacin, pirbenicillin, ticarcillin and carbenicillin, singly and in combination. For aminoglycosides, the agar MIC [minimal inhibitory concentration] were 2-3-fold greater than tube dilution MIC but for the penicillins they were similar. For aminoglycosides and ticarcillin, the MBC [minimal bactericidal concentration] were 2-fold greater than the tube dilution MIC. The MBC were not achieved at concentrations as high as 512 .mu.g/ml for 40% of the isolates for pirbenicillin and for 10% for carbenicillin. Tobramycin and pirbenicillin had the lowest MIC for the aminoglycosides and penicillins, respectively. Synergism was tested and observed between tobramycin + ticarcillin and amikacin + ticarcillin. No overall increase in resistance to gentamicin or carbenicillin was seen from 1974-1977. Patients given repeated courses of gentamicin had more resistant strains. Following the administration of 1.5 mg/kg per dose of gentamicin, peak serum concentrations failed to achieve the MIC for the microorganism in 22% of the patients. The MIC was achieved in all patients receiving the same dose of tobramycin. The overall fatality rate was 67% with 1/3 of the patients dying within 36 h. There was no relationship of patient fatality rate and MIC for the microorganism. Although in the rapidly fatal group all patients receiving inappropriate therapy died, the fatality rates of appropriately or inappropriately treated patients in the ultimately fatal and nonfatal groups were similar. Underlying host disease was the major determining factor in patient survival.