title: Cefoxitin inactivation by Bacteroides fragilis.
abstract: We have surveyed the susceptibility of 1,575 clinical isolates of the Bacteroides fragilis group of organisms to cefoxitin and eight other antimicrobial agents. Eleven isolates, 0.7% of the total, were highly cefoxitin resistant and had minimum inhibitory concentrations of greater than or equal to 64 micrograms/ml. These isolates were also resistant to other beta-lactam antibiotics. Of 11 isolates, 4 were able to inactivate cefoxitin in broth cultures, as measured by microbiological and high-pressure liquid chromatography assays. Two distinct patterns of cefoxitin breakdown products were detected by high-pressure liquid chromatography analysis. The beta-lactamase inhibitors clavulanic acid and sulbactam failed to show synergism with cefoxitin. These data demonstrate that members of the B. fragilis group have acquired a novel resistance mechanism enabling them to inactivate cefoxitin.
mesh_terms: D001441:Bacteroides fragilis / Q000378:metabolism*; D002440:Cefoxitin / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D008826:Microbial Sensitivity Tests
chemical_list: D003470:Culture Media; D002440:Cefoxitin