Brady Neuman

Background: Clostridioides difficile is a gram positive anaerobic bacteria that is a leading cause of infectious diarrhea in the United States, commonly acquired in hospital settings in patients who received antibiotic regimens that disrupt the microbiome.^1,2 The virulence of C. difficile results from its production of toxin A and toxin B, which contribute to pathogenesis and the development of severe conditions such as pseudomembrane colitis and toxic megacolon.^1,3 Current first line treatment of C. difficile infection (CDI) includes antibiotics such as vancomycin and fidaxomicin.⁴ However, usage of antibiotics to treat CDI is associated with recurrence of infection, leading to more severe outcomes and indicating a major drawback with current treatment practices.⁴ Furthermore, with increasing rates of antibiotic resistance worldwide, usage of new therapeutics alternatively or complementarily to antibiotics may be indicated to combat these issues.

Objective(s): In this narrative review, we explore recent research into Clostridioides difficile pathogenesis and the development of non-antibiotic therapeutics against C. difficile infection.

Search Methods: PubMed was used as the primary search database covering the period 2020 to 2026, using the following keywords: “Clostridioides difficile”, “toxin”, “treatment”, “antibiotic resistance”, “therapy”, and “microbiome”.

Results: Research into the effect of commensal bacteria on C. difficile growth revealed that different species have vastly different impacts on C. difficile growth in vivo.⁶ This indicates that the metabolic pathways used by gut microbiota may either enhance or protect against C. difficile infections, such that microbiome reconstitution therapy might be carefully tailored to combat infection. Furthermore, presence of human mucus in culture was found to enhance C. difficile proliferation and biofilm formation, as well as alter C. difficile metabolism, with a reciprocal impact on human lineage cells causing mucus production to shift from watery to mucoid in vitro.⁶ Further impacting our understanding of C. difficile pathogenesis is new research into a third bacterial toxin, called binary toxin, which was found to enhance growth, adhesion, and biofilm formation of C. difficile when produced in or added to culture.⁷ Binary toxin was also associated with longer infections, greater biofilm formation, increased antibiotic resistance, and decreased goblet cell density in vivo.⁷ Additionally, development of phage-delivery techniques of antitoxins has demonstrated effectiveness at neutralizing C. difficile toxins A and B, significantly increasing cultured cell viability and decreasing IL-8 and TNF-ɑ production when compared to control with toxins alone.⁸ Finally, clinically-available antitoxins have already demonstrated efficacy at preventing recurrence of C. difficile infections in clinical trials, granting credence to the use of antitoxins as therapeutic agents.⁹

Conclusions: There are multiple promising avenues emerging as potential non-antibiotic therapeutics against C. difficile infections. Deeper understanding of pathogenesis, commensal microbial interactions, and toxin production in relation to C. difficile, as well as new techniques for delivering therapeutic agents against toxins, all serve as promising launching points for combating C. difficile infections and recurrence. These new therapeutics, likely as part of combination therapy strategies, may pave the way for fighting C. difficile in the future.

Works Cited:

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2. Centers for Disease Control and Prevention. 2025. Emerging Infections Program, Healthcare-Associated Infections – Community Interface Surveillance Report, Clostridioides difficile infection (CDI), 2023
3. Kordus SL, Thomas AK, Lacy DB. Clostridioides difficile toxins: Mechanisms of Action and Antitoxin Therapeutics. Nat Rev Microbiol. 2021;20(5):285-298. doi: 10.1038/s41579-021-00660-2
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