The in-vitro activity of ceftazidime compared with that of other cephalosporins

The in-vitro activity of ceftazidime was compared with the activities of cefoperazone, cefotaxime, cefsulodin, cefuroxime, cephalothin and cefatriaxon against 331 clinical bacterial isolates. Against Escherichia coli, Salmonella, Enterobacter, Proteus mirabilis and indole-positive Proteus ceftazidime, with MIC90 of < or = 0.25 mg/l, was more active than cephalothin, cefoperazone and cefuroxime but less active than cefotaxime and ceftriaxone Klebsiella pneumoniae, Serratia, Acinetobacter and Citrobacter were inhibited at higher concentrations (MIC90 1-4 mg/l). The activity of ceftazidime against Pseudomonas aeruginosa (with MIC90 of 4 mg/l) was four times that of cefoperazone, five times that of cefatriaxon and ten times that of cefotaxime, but similar to that of cefsulodin. Against Staphylococcus aureus and Lancefield groups A and B streptococci ceftazidime was less active than the other cephalosporins. Group D streptococci were resistant. Haemophilus influenzae was inhibited by < or = 0.25 mg/l. There were no significant inoculum effects on ceftazidime and MBCs were within one twofold dilution of MICs. The addition of 50% human serum had no effect on MICs and MBCs.