In vitro activity of amoxycillin plus clavulanic acid and ticarcillin plus clavulanic acid compared with that of other antibiotics against anaerobic bacteria.

The activity of amoxycillin/clavulanic acid (Augmentin) and ticarcillin/clavulanic acid (Timentin) was tested against 303 unselected clinical anaerobic isolates recently collected in seven Belgian university hospitals and compared with that of 11 other antimicrobial agents. Bacteroides spp. accounted for 52.1% of the isolates, Clostridium spp. for 23.4%, anaerobic cocci for 15.5%, nonsporeforming gram-positive bacilli for 4.6% and Fusobacterium spp. for 3.3%. Ticarcillin/clavulanic acid (fixed clavulanic acid concentration of 2 mg/l) was the most active drug with an overall susceptibility rate of 99.7%. Amoxycillin/clavulanic acid (fixed ratio of 2:1) and chloramphenicol inhibited 97.4% of the isolates, metronidazole 95.4%, piperacillin 92.4%, ticarcillin 91.4%, clindamycin 87.8%, cefotetan 81.2%, cefazolin 63.0%, cefuroxime 60.4%, erythromycin 57.8%, penicillin 57.1% and doxycycline 52.1%. beta-lactamases were detected exclusively in Bacteroides spp. isolates (79.1% positive).