Comparative efficacies of piperacillin, azlocillin, ticarcillin, aztreonam, and tobramycin against experimental Pseudomonas aeruginosa pneumonia.

The therapeutic efficacies of the newer beta-lactam antibiotics piperacillin, azlocillin and aztreonam were compared with the efficacies of ticarcillin and tobramycin in a guinea pig model of experimental Pseudomonas aeruginosa pneumonia. For animals challenged with 2 X 10(8) CFU, tobramycin treatment resulted in survival rates and intrapulmonary killing of pseudomonads which were significantly greater than those found with any of the beta-lactam agents. There were no significant differences noted among the individual beta-lactam agents. When animals were challenged with 200-fold-fewer organisms (10(6) CFU), there was no significant difference between the efficacy of tobramycin and those of the various beta-lactams. These data suggest that tobramycin is particularly valuable in treating more severe P. aeruginosa pneumonia, whereas a number of different beta-lactam agents are of equivalent value in less severe lung infections.