The in vitro activity of ceftazidime against resistant clinical isolates.

The in vitro activity of ceftazidime was determined using an agar dilution technique and compared with that of cefotaxime and moxalactam against 559 clinically important isolates. Ceftazidime showed poor activity against Bacteroides and Campylobacter, moderate activity against Staphylococcus aureus and excellent activity against Haemophilus, Aeromonas and the Enterobacteriaceae. 91% of 324 cephalothin-resistant Enterobacteriaceae were inhibited at a concentration of 1 mg/l. Ceftazidime was the most active drug against Acinetobacter. It also showed exceptional activity against Pseudomonas, inhibiting 90% of the strains at a concentration of 4 mg/l. A significant inoculum effect was only seen with inocula of 10(6) cfu or higher, and depended on the strain tested and the methodology employed.