Micro & Immunology · single question
A patient who received an antibiotic for an abscess returns one week later with gastrointestinal complaints. The MOST likely cause is:
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Correct answer: B. Alteration of gastrointestinal flora by the antibiotic
Alteration of GI flora (dysbiosis) is the most common cause of GI upset after antibiotic therapy. Antibiotics eliminate beneficial bacteria along with pathogens, disrupting the normal microbiome, leading to nausea, diarrhea, and abdominal discomfort. This is especially common with broad-spectrum antibiotics and clindamycin (which also carries C. difficile risk). Management: probiotics, completing the course, and monitoring for C. difficile symptoms.
- A. ❌ An allergic reaction would present acutely with urticaria, pruritus, or anaphylaxis — not delayed GI complaints after completing a course.
- B. ✅ CORRECT – Antibiotic-induced dysbiosis (disruption of normal GI flora) is the most common cause of GI complaints during or after antibiotic therapy.
- C. ❌ Antibiotic-induced hepatitis is rare and presents with jaundice and elevated liver enzymes — not typical GI complaints.
- D. ❌ Secondary oral/GI candidiasis can occur after antibiotics but presents differently (oral thrush, vaginal symptoms) — not typical GI dysbiosis.
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