Are Probiotics the Answer for Recurrent Clostridioides Difficile Infection?

InpharmD™ Clinical Literature Summaries — S3E10

4 min readFeb 23, 2022


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With this podcast, we recap innovative, practice changing studies in ten minutes or less. And remember, nothing here is medical advice; we just present the evidence and our (sometimes hot) takes.

Are Probiotics the Answer for Recurrent Clostridioides Difficile Infection?

Anybody who’s worked in our healthcare system knows what a problem C. diff can be. In the hospital, patients who contract it have to isolate, and those who get active disease can be plagued by recurrence after recurrence. We’ve got antibiotics to treat the infection, but the problem is this….our antibiotics don’t kill the spore form of C diff. So even after killing all the active bacteria, there may still be spores hanging around that can germinate and cause another infection. The highest risk for recurrence is in the days to weeks that follow completion of an antibiotic course for C. diff. This is because those very antibiotics that killed C. diff, are also killing our own good bacteria, known as our microbiome. We’re learning that our gut microbiome is critical in the defense against recurrent C. diff infection. So we’re going to look at a study today where the researchers tested a novel probiotic composed of Firmicutes bacterial spores.

They randomized just under 200 adult patients with a current C. diff infection to receive the probiotic or placebo after completion of a course of antibiotics. Patients had to have had at least three C. diff infections within the past year. The probiotic was given once daily over 3 days, with ten ounces of magnesium citrate the evening before administration to decrease the inactivation of the Firmicutes spores.

Patients were monitored for a total of 8 weeks for recurrence of C. diff. The researchers found that only 12% of patients had recurrent C. diff in the probiotic group, compared to 40% in the placebo group! This equates to an absolute risk reduction of 28%, meaning the number needed to treat is just under 4!

Efficacy was seen regardless of whether vancomycin or fidaxomicin was given to treat the current infection. Additionally, both those over and under 65 derived benefit from this treatment. There was no difference in overall adverse events between probiotic group or placebo.

So, is this novel probiotic the answer to recurrent C. diff infection? Well this data sure looks promising, and the proposed mechanism of action makes sense. The researchers did some testing on the microbiome of participants in both groups and found that the value of the probiotic was faster engraftment of Firmicutes bacteria. We know that Firmicutes is a normal component of our microbiome, and it modulates the composition of our bile acids. When enough Firmicutes is present, our bile acids change in composition to a form that inhibits the germination of C. diff spores. Since most recurrences occur within a few days to 2 weeks after completing antibiotics, the delayed engraftment in the placebo group just isn’t quick enough to prevent recurrent C. diff consistently.

This new approach may provide a more consistent and safer approach than fecal microbiota transplant. While the transplant approach probably relies on similar principles, we run the risk of transmission of other pathogens that may be harmful to the recipient. The beauty of this probiotic is that we know exactly what and how much of it we’re giving, providing what may be a safer and more replicable therapeutic option.

And remember, this study was done on a very specific probiotic, so we can’t generalize these results to all probiotics. This specific Firmicutes bacteria based probiotic has been granted breakthrough designation by the FDA though, so hopefully as more data rolls in we may see a full approval, which would be a big win for patients suffering from recurrent C. diff.

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