ANTIMICROBIAL EFFECTS OF THE COMBINATION OF CEFTIBUTEN AND AN ORALLY ABSORBED PENEM SCH-29482

Ceftibuten is a new beta-lactamse-stable 3-aminothiazolyl cephalosporin that lacks activity against staphylococci and group-B streptococci. We determined the effect of the combination of ceftibuten with SCH 29482, an orally absorbed penem. The combination of the two agents was additive for 25% or indifferent for 57% of the Gram-positive species, Haemophilus, and Moraxella tested with a mean fractional inhibitory concentration (FIC) index of 0.75. The combination of ceftibuten and other Bacteroides species, all of which were inhibited by less-than-or-equal-to 2-mu-g/ml of SCH 29482. Antagonism of the combination was found for 80% of Serratia macrescens and for 30% of Citrobacter freundii and Enterobacter cloacae. Overall, the combination of ceftibuten and SCH 29482 at concentrations that can be achieved in serum after ingestion of 400 and 50 mu-g/ml, respectively, provided antibacterial activity against most Gram-positive aerobic and anaerobic species that cause upper respiratory, intraabdominal, and urinary infections.