title: Mechanism of metronidazole-resistance by isolates of nitroreductase-producing Enterococcus gallinarum and Enterococcus casseliflavus from the human intestinal tract.
abstract: Enterococcus casseliflavus and Enterococcus gallinarum strains resistant to metronidazole, nitrofurantoin and nitrofurazone were isolated from fecal samples of a patient with recurrent ulcerative colitis treated with metronidazole. Unlike other metronidazole-resistant bacteria, these strains produced nitroreductase but metabolized metronidazole to compounds that could not be detected by liquid chromatography with UV or mass spectral analysis. Metronidazole-susceptible Clostridium perfringens grew equally well in spent cultures of Enterococcus spp. incubated with or without metronidazole. These data indicate that the nitroreductases produced by these Enterococcus strains did not activate metronidazole to bactericidal metabolites and these bacteria may reduce the effectiveness of metronidazole. We have indirect evidence for an alternative pathway that results in metronidazole resistance. These strains of enterococcus had nitroreductase so resistance should not have occurred.
authors.affiliation: Division of Microbiology, National Center for Toxicological Research/FDA, Jefferson, AR 72079, USA. frafii@nctr.fda.gov
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Rafii
authors.forename: Rebecca
authors.initials: R
authors.lastname: Wynne
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Heinze
authors.forename: Donald D
authors.initials: DD
authors.lastname: Paine
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003016:Clostridium perfringens / Q000254:growth & development; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D005243:Feces / Q000382:microbiology; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D008795:Metronidazole / Q000378:metabolism* / Q000494:pharmacology*; D009601:Nitroreductases / Q000096:biosynthesis*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D008795:Metronidazole; D009601:Nitroreductases