A 10-month-old unvaccinated infant has had worsening cough for 3 weeks, now occurring in bursts of 10 to 15 coughs followed by a high-pitched inspiratory sound and post-tussive vomiting. Total leukocyte count is 32,000/mm3 with 75% small mature lymphocytes. Which is the most appropriate drug?

• A Amoxicillin for 7 days
• B Supportive care only, antibiotics have no role
• C Ceftriaxone for 10 days
• D Azithromycin for 5 days ✓

Explanation

The paroxysmal cough with whoop, post-tussive vomiting, and striking mature lymphocytosis are classic for pertussis. A macrolide is the drug of choice; azithromycin for 5 days is preferred in young children because clarithromycin and erythromycin carry a higher risk of infantile hypertrophic pyloric stenosis in very young infants. Amoxicillin is not effective against Bordetella pertussis because the organism produces beta-lactamase, so it kills the most tempting distractor.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.