Comparative bactericidal effect of ceforanide (BL-S 786) and five other cephalosporins in an in vitro pharmacokinetic model.

The bactericidal activity of ceforanide was compared, in an in vitro kinetic model, with that of five other cephalosproins: cephalothin, cefazolin, cefamandole, cefuroxime, and cefoxitin. Cultures of various pathogens in 95% human serum were incubated for 12 hours in the presence of the cephalosporins whose concentrations were modified periodically-by addition of a concentrated solution of drug or dilution with unmedicated serum-in order to simulate the variation of antibiotic concentration in human blood after one-gram intramuscular dose. One Gram-positive strain and six Gram-negative strains were used. Bactericidal activity was assessed by monitoring changes in the number of colony-forming units. Tests showed that against Klebsiella pneumoniae, ceforanide was the most active of the six cephalosporins. Proteus mirabilis was more susceptible to ceforanide and cefuroxime than to the other compounds; Enterobacter cloacae to ceforanide, cefuroxime, and cefamandole; Escherichia coli to ceforanide, cefuroxime, cefamandole, and cefazolin. The number of viable cells of Staphylococcus aureus was reduced below detectable levels by all cephalosporins except cefoxitin. On the other hand, Providencia stuartii was virtually unaffected by all of the cephalosporins except cefoxitin.