A comparative study of the activity of first and second generation cephalosporins and their combinations with beta-lactamase inhibitors against Bacteroides fragilis.

The sensitivity of 160 strains of Bacteroides fragilis, 74 beta-lactamase-positive and 86 negative, to two first generation and four second generation cephalosporins, alone and in combination with clavulanic acid and sulbactam, was investigated. For the susceptibility test the dilution method in agar was used. The detection of beta-lactamase production by this micro-organism was performed by means of the method using chromogenic cephalosporin of Nitrocefin. In both strains an important improvement in the activity of cephalothin, cephazolin, cefonicid and cefamandole was noted when they were combined with the two inhibitors. In combinations of cefoxitin and cefmetazole, no significant improvement was evident in the values of the parameters studied in the beta-lactamase-producing strains; and even in beta-lactamase-negative strains these values showed only a slight increase.