title: Effect of highly potent antipseudomonal beta-lactam agents alone and in combination with aminoglycosides against Pseudomonas aeruginosa.
abstract: The activities of ticarcillin, cefsulodin, ceftazidime, aztreonam, and imipenem, formerly known as N-formimidoyl thienamycin, were evaluated alone and in combination with aminoglycosides against 56 clinical isolates of Pseudomonas aeruginosa, which were characterized by aminoglycoside susceptibility and content of aminoglycoside-modifying enzymatic activities. All beta-lactam agents were highly active against aminoglycoside-susceptible isolates, and with few exceptions the aminoglycoside-resistant isolates were susceptible to all of the beta-lactam agents except ticarcillin. Combinations of the beta-lactam agents with aminoglycosides frequently acted synergistically, but the effect of different beta-lactam agents in combination with an aminoglycoside against individual strains was unpredictable. The presence or absence of an aminoglycoside-modifying enzymatic activity had no observed effect on synergism with tobramycin. Killing-curve experiments with strains in the presence of concentrations of a beta-lactam and an aminoglycoside that were not bactericidal alone (one-fourth the minimal bactericidal concentration) showed synergistic bactericidal action against four strains that were tested. The results demonstrate the great activity of these newer antipseudomonal beta-lactam agents and their potential for synergism with aminoglycosides.
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001398:Aztreonam / Q000494:pharmacology; D002441:Cefsulodin / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D004357:Drug Synergism; D006801:Humans; D015378:Imipenem; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D013845:Thienamycins / Q000494:pharmacology; D013982:Ticarcillin / Q000494:pharmacology
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D013845:Thienamycins; D015378:Imipenem; D002442:Ceftazidime; D013982:Ticarcillin; D001398:Aztreonam; D002441:Cefsulodin