Comparative in-vitro activities of cefpiramide and other β-lactam antibiotics

The in-vitro activities of cefpiramide were compared to those of cefoperazone, ceftazidime, ceftizoxime, ceftriaxone, cefsulodin, moxalactam, aztreonam, piperacillin and gentamicin against 735 clinical isolates. The minimum inhibitory concentration (MIC) was determined by a broth-dilution method. Susceptibility to cefpiramide (MIC ≤64 μg/ml) was found for 89.1% of 487 Enterobacteriaceae, for 94.0% of 50 Pseudomonas aeruginosa and for 81.1% of 37 Acinetobacter. Cefpiramide was one of the most active agents tested against Pseudomonas aeruginosa, as indicated by an MIC for 50% and for 90% of the isolates, which were 4 and 32 μg/ml, respectively. The MIC for 50% of the isolates were either 2 or 4 μg of cefpiramide per ml for 10 to 16 species of Enterobacteriaceae, but values for most other cephalosporins were even lower. Hemophilus influenzae, Staphylococcus aureus and enterococci were uniformly susceptible to cefpiramide and the MIC for 90% of the isolates were 4, 8 and 32 μg/ml, respectively. The in-vitro activities of cefpiramide most closely resembled those of cefoperazone, although with less potent action against Enterobacteriaceae, but greater intrinsic activity against Pseudomonas aeruginosa, Acinetobacter and enterococci.