The in-vivo antibacterial activity of ceftazidime (Gr 20263)--a comparison with other new beta-lactam antibiotics and gentamicin.

Ceftazidime was compared with cefotaxime, ceftizoxime, cefmenoxime, cefotiam, cefoperazone, moxalactam, piperacillin, carbenicillin, mezlocillin, cefsulodin and the aminoglycoside antibiotic gentamicin in a series of mouse protection tests. Ceftazidime, together with the other cephalosporin antibiotics and moxalactam were equally effective against infections caused by Staphylococcus aureus with ED50 values ranging from 3.5 to 25 mg/kg. Gentamicin was the most active antibiotic with ED50 values of 0.4 and 1.6 mg/kg. Ceftazidime showed excellent activity against Enterobacteriaceae with ED50 values ranging from 0.2-0.9 mg/kg for Escherichia coli strains, 1.1-13.8 mg/kg for indole positive and negative Proteus spp, and 0.1-25 for Enterobacter cloacae, Klebsiella pneumoniae and Serratia spp. Similar activity against many of the test strains of Enterobacteriaceae was found for gentamicin, cefotaxime, ceftizoxime, cefmenoxime and moxalactam, although cefotiam and cefoperazone were significantly less active than ceftazidime. Ceftazidime was significantly more active than the other beta-lactam antibiotics tested against Pseudomonas aeruginosa infections with ED50 values ranging from 02-108 mg/kg. Only the aminoglycoside antibiotic gentamicin, with ED(50,S) 0.6-6.3 mg/kg, was as effective as ceftazidime. Very poor activity was found for moxalactam, cefoperazone, piperacillin, carbenicillin and mezlocillin against the majority of the test strains of Pseudomonas. The results of these in-vivo indicate that ceftazidime is a promising potential alternative to aminoglycoside antibiotics.