title: Inactivation of metronidazole by Enterococcus faecalis.
abstract: The in-vitro inactivation of metronidazole by different clinical isolates of Enterococcus faecalis was investigated by means of association experiments in which Ent. faecalis strains and Bacteroides fragilis group strains were cultured in the same liquid medium. All of the tested Ent. faecalis strains (20 isolates) were able to protect the B. fragilis group strains against the killing effect of metronidazole at a concentration four or eight times higher than the normal MIC. Different strains of Streptococcus (14), Staphylococcus aureus (10), Staph, epidermidis (10) and Escherichia coli (8) failed to exhibit the same effect. When Ent. faecalis strains were cultured anaerobically for 24 h in the presence of 4 mg metronidazole/l, either alone or together with different B. fragilis group strains, no metronidazole could be detected subsequently in the culture supernatants by HPLC. Concomitantly an increase of four or five logs in the viable counts of the co-cultured Bacteroides strains was observed compared with Bacteroides strains cultured alone. Sonicated cell extracts of Ent. faecalis cultured either aerobically or anaerobically were found to inactivate metronidazole to the same extent, whereas the culture supernatants had no such effect.
authors.affiliation: Department of Clinical Microbiology, Albert Szent-Györgyi Medical University, Szeged, Hungary.
authors.forename: E
authors.initials: E
authors.lastname: Nagy
authors.forename: J
authors.initials: J
authors.lastname: Földes
mesh_terms: D001431:Bacteriological Techniques; D001441:Bacteroides fragilis / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D015169:Colony Count, Microbial; D013293:Enterococcus faecalis / Q000378:metabolism*; D008795:Metronidazole / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D008795:Metronidazole