Reversion of heme-dependent metronidazole resistance in <i>Clostridioides difficile</i>

Metronidazole (MTZ) is a widely used antibiotic for treating anaerobic bacterial infections, including <i>Clostridioides difficile</i> infection. However, the increasing emergence of MTZ resistance among anaerobic pathogens poses a significant threat to its continued clinical effectiveness. Heme-dependent MTZ resistance, one of the mechanisms of resistance, has been associated with poorer treatment outcomes in patients. In this study, we identified artemisinin (ART) and demonstrated that it can reverse heme-dependent MTZ resistance in diverse clinical isolates of <i>C. difficile</i>. Furthermore, ART effectively reversed resistance mediated by the nim genes in both <i>C. difficile</i> and <i>Bacteroides fragilis</i>. These findings open a possible avenue for restoring the efficacy of MTZ against resistant anaerobic bacteria, particularly those with the Nim-mediated resistance mechanism.