The preferred oral agent for a symptomatic Bacillus cereus diarrheal infection in an otherwise healthy adult is a fluoroquinolone. Give ciprofloxacin 500 mg by mouth twice daily for 5–7 days (or levofloxacin 750 mg once daily for 5 days if ciprofloxacin is unavailable or not tolerated). If fluoroquinolones cannot be used, clindamycin 300 mg by mouth four times daily for 7 days is an acceptable second‑line option. Beta‑lactam antibiotics (including amoxicillin‑clavulanate) are generally avoided because B. cereus frequently produces beta‑lactamases and may be resistant. Monitor the patient for resolution of loose stools and any adverse drug effects; if symptoms persist beyond a week or worsen, reassess for alternative diagnoses or need for intravenous therapy.
What is the best oral antibiotic for treating Bacillus cereus diarrheal infection in a healthy adult?
Last updated: March 8, 2026 • View editorial policy
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