COMPARATIVE SERUM BACTERICIDAL ACTIVITY AGAINST PSEUDOMONAS-AERUGINOSA OF 6 ANTIPSEUDOMONAL AGENTS

Serum levels and serum bactericidal activities of six antipseudomonal agents were studied comparatively in 60 patients. Single intravenous d oses of gentamicin (1.5 mg/kg), piperacillin (4 g), ceftazidime (1 g), imipenem (0.5 g), aztreonam (1 g), and ciprofloxacin (200 mg) were gi ven over 30 min to 10 patients each, and serum samples were obtained 3 0 min, 1, 2, 3, 4, 6, 8 and 12 h after beginning the infusion. Serum b actericidal activity was determined by the broth microdilution method against 10 recent isolates of Pseudomonas aeruginosa. Mean peak serum levels were as follows: gentamicin 10.4 mu g/ml, piperacillin 227.5 mu g/ml, ceftazidime 43.5 mu g/ml, imipenem 17.3 mu g/ml, aztreonam 42.3 mu g/ml, and ciprofloxacin 3.9 mu g/ml. All agents demonstrated effec tive serum bactericidal activity (geometric mean titer >1:2) at peak s erum levels. Ceftazidime was by far the most potent compound with a me an titer of 1:46.5, followed by ciprofloxacin (1:17), imipenem (1:13.7 ), and aztreonam (1:13.4). Ceftazidime also showed the longest duratio n of activity with a mean titer of 1:5.1 at 4 h. Based on our results, ceftazidime appeared to be the most potent antipseudomonal agent, whi le gentamicin and piperacillin were the least effective.