AUGMENTATION EFFECT OF CLAVULANIC ACID WITH PENICILLIN, CEPHALOTHIN AND TICARCILLIN AGAINST BACTEROIDES-FRAGILIS

The effect of clavulanic acid on the in vitro activity of .beta.-lactam antibiotics against B. fragilis (154 strains) was tested. The MIC90 [90% minimum inhibtory concentration] on 154 strains of B. fragilis tested was > 64 .mu.g/ml for penicillin and cephalothin, and > 128 for ticarcillin alone. Thirty-two strains of B. fragilis relatively resistant to the test .beta.-lactam antibiotics (most of them .beta.-lactamase producers) were retested with the addition of clavulanic acid. Ninety percent of the strains were then inhibited by .ltoreq. 8 .mu.g/ml of pencillin and cephalothin, and by 32 .mu.g/ml of ticarcillin. The strongest .beta.-lactamase producers were the most susceptible, and this was not influenced by change in pH of the diluent for clavulanic acid from 6.0 to 7.4. Both penicillin and cephalothin when combined with clavulanic acid were highly effective against B. fragilis but the therapuetic relevance of these combinations remains to be evaluated.