Comparative in vitro activity of aztreonam, other beta-lactam antibiotics and aminoglycosides against Pseudomonas aeruginosa

Aztreonam, ceftriaxone, moxalactam, cefotaxime, cefsulodin, cefoperazone, piperacillin, azlocillin, carbenicillin, amikacin, gentamicin, tobramycin, sisomicin and dibekacin were tested by broth dilution against 161 isolates of Pseudomonas aeruginosa. Seventy-one of these strains were selected for their resistance to carbenicillin and aminoglycosides and classified as 'multiply resistant' strains. Over all, aztreonam showed the greatest antipseudomonal activity by far, followed by ceftriaxone, moxalactam, cefotaxime and amikacin. Piperacillin, azlocillin, cefsulodin, and cefoperazone were highly active against carbenicillin and/or aminoglycoside-susceptible P. aeruginosa strains, but were also poorly inhibitory against multiply resistant isolates.