Comparative disk and broth dilution susceptibility test results with ticarcillin and timentin against Pseudomonas aeruginosa and Pseudomonas maltophilia.
A total of 500 clinical isolates of Pseudomonas aeruginosa and 14 isolates of Pseudomonas maltophilia were examined for susceptibility to ticarcillin and timentin (ticarcillin plus clavulanic acid). Clavulanic acid enhanced the activity of ticarcillin against only 34 of 500 isolates of P. aeruginosa. Among 23 isolates of P. aeruginosa, that had yielded divergent disk diffusion results, there were 3 major discrepancies (3 = ticarcillin-resistant by disk diffusion, but susceptible by broth dilution test criteria) and 1 very major discrepancy (timentin-susceptible by disk diffusion, but resistant by broth dilution test criteria). Clavulanic acid enhanced the activity of ticarcillin against 12 of 14 isolates of P. maltophilia; there were 2 major discrepancies (ticarcillin resistance in terms of disk diffusion, but susceptibility according to ticarcillin MICs). Consequently, it was decided to continue employing timentin disks alone, rather than add ticarcillin disks in our Bauer-Kirby test battery for Pseudomonadaceae.
D002969:Clavulanic Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D010406:Penicillins / Q000494:pharmacology*; D011549:Pseudomonas / Q000187:drug effects*; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D013982:Ticarcillin / Q000494:pharmacology*; D065093:beta-Lactamase Inhibitors
D002969:Clavulanic Acids; D004338:Drug Combinations; D010406:Penicillins; D065093:beta-Lactamase Inhibitors; C043215:ticarcillin-clavulanic acid; D013982:Ticarcillin