Clostridioides difficile Infection — ABIM Board MCQ

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ModerateInfectious DiseasesClostridioides difficile InfectionABIM Board

A 64-year-old woman presents with her first episode of nonsevere Clostridioides difficile infection (WBC 11,200/µL; creatinine 0.9 mg/dL). What is the preferred initial therapy?

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Correct answer: D — Oral fidaxomicin 200 mg twice daily for 10 days

The 2021 IDSA/SHEA Focused Update shifted from vancomycin-first to fidaxomicin-first for initial CDI (both nonsevere and severe). Fidaxomicin has a narrower spectrum, less disruption of gut flora, and lower recurrence rates than vancomycin. This patient's lab values (WBC 11.2K, Cr 0.9) define nonsevere disease. Option B (vancomycin) remains acceptable but is no longer preferred; the stem's claim that it is "preferred first-line" contradicts current guidance. Metronidazole (A) is relegated to situations where vancomycin and fidaxomicin are unavailable. Bezlotoxumab (E) is adjunctive, used in recurrent CDI, not monotherapy for initial infection. Probiotics (C) lack evidence for CDI treatment. Fidaxomicin 200 mg BID for 10 days (D) aligns with current guideline recommendations.

Reference: SHEA/IDSA 2021 Clinical Practice Guideline Update for the Management of Clostridioides difficile Infection in Adults. https://www.idsociety.org/practice-guideline/clostridioides-difficile-2021-focused-update/