In vitro and in vivo microbiological evaluations of cefoperazone

Evaluations of minimum inhibitory concentrations MICs) were carried out with cefoperazone on 35 gram-positive, 60 gram-negative, and 64 anaerobic strains. Results were compared to those obtained with cefuroxime, cefoxitin, cephaloridine, cefazolin, cephalexin and (for the anaerobic bacteria only) cephalothin. In vitro activity of cefoperazone was excellent against strains of Streptococcus faecalis (MICs between 6.25 and 12.5 μg/ml) and Staphylococcus aureus (100% of the tested strains were inhibited by ≤ 12.5 μg/ml). Cefoperazone activity against gram-negative strains was superior to that of all the other cephalosporins tested. It is noteworthy that all of the Proteus species and Pseudomonas aeruginosa strains were inhibited by ≤ 50 μg/ml cefoperazone, a level readily achievable in serum with normal dosages. All Escherichia coli were inhibited by ≤ 1.56 μg/ml. In vitro activity of cefoperazone was extremely high against anaerobic bacteria: 100% of the strains tested were susceptible at ≤ 1.56 μg/ml. The PD50 values in experimental infections in mice confirmed the high in vitro activity of cefoperazone, with lower doses required for protection than for the other cephalosporins tested. This may be due to the favorable pharmacokinetics of cefoperazone. The stability of cefoperazone in the presence of beta-lactamase was also confirmed.