In vitro antibacterial activity of cefoperazone (T-1551), a new semisynthetic cephalosporin.

Cefoperazone, a new semisynthetic cephalosporin, has a broad spectrum of antibacterial activity. It is as active as cefazolin and cefamandole against gram-positive bacteria and is more active than cefazolin and cefamandole against such gram-negative bacilli as Escherichia coli, Klebsiella pneumoniae, Proteus species, Pseudomonas aeruginosa, Citrobacter freundii, Enterobacter cloacae, and Serratia marcescens. The superiority of cefoperazone over cefazolin and cefamandole with respect to activity against P. aeruginosa by more than 200-fold was especially remarkable. As with other beta-lactam antibiotics, there was only a small spread between the minimum inhibitory concentrations and the minimum bactericidal concentrations of cefoperazone and a significant decrease in activity with an increase in inoculum size. Activity was not altered significantly by the addition of human serum to the test medium. Cefoperazone is relatively stable to hydrolysis to beta-lactamases produced by gram-negative bacteria. Relative rates of hydrolysis of cefoperazone by cephalosporinases are 7.0 to 0.01, with reference to cephaloridine hydrolysis (base, 100). Cefoperazone is also more stable than penicillin G and cephaloridine to various types of penicillinases.