In-vitro activity of ceftazidime, a beta-lactamase stable cephalosporin

The in-vitro activity and beta-lactamase stability of ceftazidime were evaluated against 700 Gram-positive and Gram-negative bacteria. Ceftazidime was less active than penicillins or older cephalosporins against Staphylococcus spp. and Streptococcus spp., and it did not inhibit Streptococcusfaecalis. However, ceftazidime was as active as moxalactam and cefoperazone against Escherichia coli, Klebsiella and Proteus mirabilis with MICs less than 0.2 mg/l. Ceftazidime also inhibited Enterobacter, Citrobacter, Salmonella and Shigella at concentrations below 0.2 mg/l. Most Morganella, Pr. rettgeri, Pr. vulgaris and Pr. inconstans were inhibited at concentrations below 1 mg/l similar to concentrations for moxalactam, cefoperazone, and cefotaxime. Ceftazidime was the most active agent tested against Ps. aeruginosa, with a mean MIC of 1.6 mg/l. It inhibited carbenicillin, piperacillin, cefoperazone, cefsulodin resistant Pseudomonas.