PURIFICATION AND CHARACTERIZATION OF AN IMIPENEM HYDROLYZING METALLO-BETA-LACTAMASE FROM BACTEROIDES-FRAGILIS

An imipenem resistant β-lactamase producing strain of Bacteroides fragilis was isolated from a clinical specimen. The specific activity of the unpurified β-lactamase was 5-•5 U/mg protein. The β-lactamase was purified 60-fold by Q Sepharose, Sephacryl S-300 and Mono Q column passages. The strain was able to inactivate imipenem and cefoxitin in broth cultures. The enzyme hydrolysed imipenem more rapidly than ampicillin, benzylpcnicillin, cephalothin and cefoxitin. The activity of the enzyme was Zn2+ dependent and was completely inhibited by EDTA. The inhibition was reversed by ZnSO4. Preincubation with the common β-lactamase inhibitors clavulanic acid, sulbactam and tazobactam did not reduce the enzyme activity. The molecular weight was determined by sodium dodecyl sulfate gradient gel clectrophoresis to be 31,000 Daltons and the isoelectric point was 4·5. © 1992 by The British Society for Antimicrobial Chemotherapy.