In vitro activity of ceftazidime and ceftriaxone

The in vitro susceptibility of 230 clinical isolates, including 55 anaerobic bacteria, was tested with ceftazidime, ceftriaxone, cefotaxime, cefoperazone, moxalactam, cefamandole, cefoxitin, and ticarcillin. Ceftazidime was the most active drug against Pseudomonas aeruginosa and Acinetobacter sp. Against Enterobacteriaceae, ceftazidime and ceftriaxone were similar to cefotaxime, moxalactam, and cefoperazone and more active than cefamandole, cefoxitin, and ticarcillin. Cefoxitin and moxalactam were significantly more active against Bacteroides fragilis than were the other beta-lactam drugs. Against Staphylococcus aureus, ceftriaxone showed moderate activity, while ceftazidime was relatively inactive. These results indicate a potential role for ceftazidime and ceftriaxone against infections involving facultative and aerobic gram-negative bacilli.