Isolation and properties of metronidazole-resistant mutants of Bacteroides fragilis.

Metronidazole-resistant mutants of Bacteroides fragilis, isolated after mutagenesis, had diminished ability to take up and metabolize the drug. All the metronidazole-resistant strains had depressed levels of pyruvate dehydrogenase compared with parent cultures. Their end products of glucose metabolism also differed from normal B. fragilis products and were consistent with deficiencies in pyruvate dehydrogenase activity.