Ridinilazole Preserves Gut Microbiome Diversity in Treatment of C difficile Infection

C Diffcile bacterium
C Diffcile bacterium
Compared with fidaxomicin, ridinilazole preserved gut microbiome diversity to a greater extent in the treatment of Clostridium difficile infection.
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SAN DIEGO – Treatment of Clostridium difficile infection with ridinilazole retained gut microbiome diversity during and after a 10-day regimen better than treatment with fidaxomicin, and both treatments had similar levels of reduction in C difficile, according to research presented at IDWeek 2017.

Researchers measured fecal microbiome diversity of participants in a phase 2 study that compared ridinilazole with fidaxomicin over the course of 10 days. Microbiome diversity was measured with Illumina sequencing using fecal samples collected throughout the study, from study entry to day 40.

At 30 days posttherapy, similar sustained clinical response rates were noted for ridinilazole and fidaxomicin (50% and 46.2%; estimated treatment difference, 2.9%, 95% CI, −30.8% to 36.7%). 

At the level of taxonomical families, participants receiving ridinilazole had significantly more microbiome diversity compared with those receiving fidaxomicin. When the samples were stratified by the receipt of concomitant or prior antibiotics at baseline, the difference in microbiome diversity was greatest in those samples that had received no prior or concomitant antibiotics.

Bifidobacteriaceae and Ruminococcaceae populations, which the study authors mentioned had been previously linked to colonization resistance, were better preserved in patients treated with ridinilazole compared with those treated with fidaxomicin.

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The study authors concluded that “[Ridinilazole] preserved gut microbiome diversity to a greater extent than [fidaxomicin] during [C difficile] treatment. Differences were most marked for, but not restricted to, patients receiving no [concomitant antibiotics]. Microbiome sparing by [ridinilazole] is consistent with low [C difficile] recurrence rates.”


Caroline Chilton, PhD, Jane Freeman, PhD, Richard Vickers, PhD, and Mark Wilcox, MD, have reported disclosures. The remaining authors have nothing to disclose. A full listing of disclosures can be viewed here.

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Mitra S, Chilton C, Freeman J, et al. Preservation of gut microbiome following ridinilazole versus fidaxomicin treatment of Clostridium difficile infection. Presented at: IDWeek 2017; October 4-8, 2017; San Diego, CA. Poster 1842.