In-vitro comparison of ceftazidime and nine other antimicrobial agents against hospital strains of Gram-negative bacteria.

The agar dilution in-vitro susceptibility of 370 isolates of aerobic Gram-negative bacteria isolated at Ben Taub General Hospital in Houston, Texas were determined for five new and five currently available agents. Ceftazidime, moxalactam, cefotaxime, ceftizoxime and cefoperazone, all of which are new beta-lactam compounds, were compared with two penicillins, piperacillin, ticarcillin, and three aminoglycosides, gentamicin, tobramycin and amikacin. Ceftazidime inhibited 100% of pseudomonas strains at a concentration of 12.5 mg/l, whereas the aminoglycosides inhibited 88-93% and ticarcillin and piperacillin inhibited 47 and 85% of these strains at this concentration. Ceftazidime at a level of 125 mg/l was the most effective agent against all strains of indole positive Proteus spp., Serratia spp., Klebsiella spp., Citrobacter spp., and Echerichia coli. Moxalactam was the most effective agent against Enterobacter spp., and ceftazidime was the next most effective agent. Ceftazidime is a potent new beta-lactam which should be useful against hospital strains of Gram-negative bacteria.