Mechanism of metronidazole-resistance by isolates of nitroreductase-producingEnterococcus gallinarumandEnterococcus casseliflavusfrom 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.

Response of antimicrobial nitrofurazone-degrading biocathode communities to different cathode potentials

“…Previous studies have found that Enterococcus is often enriched in the nitroaromatic nitrobenzene-reducing biocathode communities, and the relative abundance can reach 38.4% or 74.7% (Wang et al, 2011). This was consistent with the fact that Enterococcus and Pseudomonas species own nitroaromaticsreducing ability (Rafii et al, 2003;Roldan et al, 2008). These results indicated that the microbial community structure with applied electrical stimulation was obviously different from that of the open circuit biofilm.…”

Effect of broad- and narrow-spectrum antimicrobials on Clostridium difficile and microbial diversity in a model of the distal colon

“…1B). This inability to recover metronidazole has been previously noted (18), and it has been suggested that inactivation of metronidazole by human gut microbiota such as enterococci may be responsible for the lack of activity (19,20).…”

Microbial community structure and function of Nitrobenzene reduction biocathode in response to carbon source switchover

“…For example, Dysgonomonas and Escherichia could ferment glucose with production of volatile acid under facultative anaerobic conditions were enriched in the initial inoculum. Enterococcus (38.42%) and Raoultella (11.09%) dominated in the gBC attributed to they could reduce nitroaromatics into corresponding aromatic amines under heterotrophic cultivation (Claus et al, 2006;Rafii et al, 2003). …”