In vitro activity and in vivo evaluation of ticarcillin plus clavulanic acid against aerobic and anaerobic bacteria.

The efficacy of ticarcillin plus clavulanic acid was compared with that of certain broad-spectrum antibiotics such as ticarcillin, azlocillin, and piperacillin against blood culture isolates of aerobic bacteria obtained from seriously ill patients and anaerobic bacteria obtained from other miscellaneous infections. Ticarcillin plus clavulanic acid was found to be as effective as other broad-spectrum antibiotics against most of the 285 septicemic isolates tested. Ticarcillin plus clavulanic acid was most effective against 351 anaerobic bacteria, including B. fragilis. Further, 32 strains of B. fragilis that were relatively resistant to ticarcillin and azlocillin were tested with a mixture of ticarcillin or azlocillin, each in combination with clavulanic acid. Ticarcillin plus clavulanic acid inhibited all 32 strains of B. fragilis. Addition of clavulanic acid to cephalothin, penicillin, or azlocillin also augmented the antibiotic activity against B. fragilis by 4- to 64-fold. These in vitro data suggest that ticarcillin plus clavulanic acid may be used as a single antibiotic in the cases of bacterial septicemias and that the combination may be used in the treatment of multiple-antibiotic-resistant bacterial strains. In a related study, the augmentation activity of clavulanic acid with penicillin or ticarcillin was evaluated against B. fragilis in a rat intra-abdominal abscess model. Gelatin capsules filled with a mixture of B. fragilis and Escherichia coli were implanted intraperitoneally in male Wistar rats. Four different groups of animals with appropriate controls were treated with penicillin or ticarcillin alone or in combination with clavulanic acid. Treatment was started immediately or delayed for 48 hours after peritoneal soilage. The mortality rate decreased by almost one half when antibiotic therapy was started immediately. Treatment with ticarcillin plus clavulanic acid resulted in a cure in 70 to 89 percent of animals, showing that this combination is the most effective regimen in the treatment of rats with experimental intra-abdominal abscesses caused by B. fragilis and E. coli.