American Board of Internal Medicine (ABIM) Certification Practice Exam

Which antibiotics are typically prescribed for diarrhea caused by Shigella?

1. Amoxicillin × 5 days

2. Fluoroquinolone × 3 days; azithromycin × 3 days

3. Vancomycin × 7 days

4. Fluoroquinolone × 3 days; azithromycin × 5 days

The correct answer is: Fluoroquinolone × 3 days; azithromycin × 3 days

Diarrhea caused by Shigella is primarily treated with antibiotics to reduce both the duration of illness and the shedding of the bacteria, which is crucial in preventing transmission. The recommended treatment options include fluoroquinolones and azithromycin, with fluoroquinolones being particularly effective against Shigella species, especially in adults. Azithromycin is often used as an alternative, particularly in pediatric populations or in areas where fluoroquinolone resistance is prevalent. The choice of a fluoroquinolone for a duration of three days, along with azithromycin for the same duration, is effective because both antibiotics can target Shigella and have good penetration into the enteric tissues where the bacteria proliferate. This combination can also be beneficial in terms of addressing potential resistance patterns while ensuring effective coverage. Prolonging the duration of treatment is generally unnecessary, as a three-day course is sufficient for most cases. Thus, the combination of fluoroquinolone and azithromycin for three days offers a balanced and effective approach to managing Shigella infections, making this the appropriate recommendation for treatment.