The in-vitro properties of ceftazidime

Ceftazidime showed a high level of in-vitro antibacterial activity against the Enterobacteriaceae with geometric mean MICs of 0.07-0.5 mg/l and at least 90% of isolates sensitive to 8 mg/l. This cephalosporin was at least as active as gentamicin against gentamicin-sensitive Enterobacteriaceae and showed no significant reduction in activity against gentamicin-resistant strains. The activity of ceftazidime against Pseudomonas species was of special note with all the 204 isolates tested sensitive to 8 mg/l and was highly active against gentamicin-resistant strains. Activity against Staphylococcus aureus was moderate, whilst streptococci were highly susceptible. Activity against Bacteroides fragilis was moderate but a range of anaerobic bacilli and cocci were sensitive. Ceftazidime showed no significant inoculum effects, was rapidly bactericidal and as stable as cefoxitin to a wide range of cell-free beta-lactamases. The spectrum and activity of ceftazidime suggest that it may replace the aminoglycosides currently in clinical use.