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Multiply recurrent Clostridioides difficile infection — ABIM Board MCQ

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HardClostridioides difficile InfectionMultiply recurrent Clostridioides difficile infectionABIM Board

A 72-year-old man is completing fidaxomicin for his third toxin-confirmed episode of Clostridioides difficile infection within 9 months. His diarrhea resolved 3 days ago, and he now has one formed bowel movement daily. He has stage 4 chronic kidney disease with an estimated glomerular filtration rate of 18 mL/min/1.73 m²; his nephrologist recommends avoiding magnesium-containing cathartics. He has no ileus or toxic megacolon and can swallow capsules. To reduce the risk of another recurrence, the patient elects treatment with fecal microbiota spores, live-brpk (Vowst). Which of the following is the most appropriate administration plan?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Initiate four capsules daily 48 hours after fidaxomicin, preceded by 250 mL of polyethylene glycol electrolyte solution

Explanation lettering: C = shown as B · E = shown as C · B = shown as D · D = shown as E

This patient has multiply recurrent CDI, has completed appropriate antibacterial treatment with clinical resolution, and has elected an FDA-approved oral microbiota product to prevent another recurrence. Vowst is preventive therapy rather than treatment of active CDI. It should be started 2–4 days after completion of the antibacterial regimen; antibacterials should not be administered concurrently because they may impair the live microbiota product. The labeled dose is four capsules taken together on an empty stomach before the first meal of the day for 3 consecutive days. Bowel preparation is given the day before and at least 8 hours before the first dose. Because this patient has advanced kidney disease and has been advised to avoid magnesium, the label-supported alternative is 250 mL of polyethylene glycol electrolyte solution. A is incorrect because Vowst should not overlap with fidaxomicin. B uses an appropriate total daily dose but starts too early and uses a magnesium-containing preparation despite advanced kidney disease. C uses the correct interval and preparation but incorrectly divides the four-capsule dose throughout the day. D uses the correct dose and renal-appropriate preparation but delays treatment beyond the labeled 2–4-day post-antibiotic window. E correctly integrates the indication, sequence, renal preparation exception, timing, and dosing regimen.

Reference: Package Insert—VOWST (fecal microbiota spores, live-brpk) (Initial US approval April 26, 2023; checked August 27, 2026) — https://www.fda.gov/files/vaccines%2C%20blood%20%26%20biologics/published/Package-Insert-VOWST.pdf FDA Approves First Orally Administered Fecal Microbiota Product for the Prevention of Recurrence of Clostridioides difficile Infection (April 26, 2023) — https://www.fda.gov/news-events/press-announcements/fda-approves-first-orally-administered-fecal-microbiota-product-prevention-recurrence-clostridioides SHEA/IDSA 2021 Clinical Practice Guideline Update for the Management of Clostridioides difficile Infection in Adults (June 14, 2021) — https://www.idsociety.org/practice-guideline/clostridioides-difficile-2021-focused-update/