Simultaneous resistance to metronidazole, co-amoxiclav, and imipenem in clinical isolate of Bacteroides fragilis.

A blood-culture isolate of Bacteroides fragilis, taken from a woman after elective laparotomy, was resistant to metronidazole and had reduced susceptibility to imipenem and co-amoxiclav. After treatment with imipenem, pus drained from the pleural cavity yielded an identical isolate that had become highly resistant to imipenem and co-amoxiclav. Emergence of full resistance to the beta-lactam antibiotics was accompanied by a tenfold rise in the specific activity of a metallo-beta-lactamase. Clinicians need to be alert to simultaneous resistance to metronidazole, co-amoxiclav, and imipenem and development of high-level resistance to imipenem in B fragilis during treatment with this agent.