PSEUDOMONAS-AERUGINOSA - BACTERICIDAL ACT IVITY OF 8 ANTIBIOTICS AND 7 COMBINATIONS FOR VARIOUS BETA-LACTAMS RESISTANCE PHENOTYPE

Bactericidal activities of 8 antibiotics (ticarcillin, piperacillin, p iperacillin-tazobactam, ceftazidime, cefepime, imipenem, amikacin, cip rofloxacin) and of 7 combinations have been studied by time-killing cu rve technique for 16 Pseudomonas aeruginosa selected for their beta-la ctams resistance phenotypes (3 wild strains, 5 penicillinases, 2 exten ded-spectrum beta-lactamases, 3 high level cephalosporinases and 3 non enzymatic resistance). Bactericidal activities of beta-lactams used a lone were as follows: imipenem > cefepime > ceftazidime, piperacillin, piperacillin-tazobactam > ticarcillin. All the antibiotics combinatio ns were synergistic or additiv. However, only the combination of imipe nem with amikacin was bactericidal for all strains. For the strains wi th penicillinases, piperacillin-tazobactam was not more effective than piperacillin. For the extended-spectrum beta-lactamases, we have obse rved a synergy with piperacillin-tazobactam and ciprofloxacin or amika cin.