A 28-year-old man from rural Rajasthan presents with a 3-week history of watery diarrhea, crampy abdominal pain, and low-grade fever. Stool culture grows a Gram-negative, S-shaped, microaerophilic bacillus that is oxidase-positive and hippurate-positive. What is the most appropriate next step in management?

Explanation

## Diagnosis and Clinical Context The clinical presentation and laboratory findings are pathognomonic for **Campylobacter jejuni** infection: - Gram-negative, S-shaped (comma or spiral-shaped) bacillus - Oxidase-positive and hippurate-positive (key identification test) - Microaerophilic growth requirement - Acute gastroenteritis with diarrhea, cramping, and fever **Key Point:** Campylobacter jejuni is the most common bacterial cause of acute gastroenteritis worldwide and a leading cause in India, particularly in rural populations with poor sanitation. ## Management Approach ### Indications for Antimicrobial Therapy Campylobacter gastroenteritis requires antibiotic treatment when: - Severe or prolonged diarrhea (>1 week) - Bloody diarrhea - High fever or systemic toxicity - Immunocompromised host - Early treatment (within 3 days of symptom onset) reduces duration This patient has had symptoms for 3 weeks, indicating severe/prolonged disease warranting therapy. ### First-Line Antibiotic Choice | Antibiotic | Dose | Duration | Notes | |---|---|---|---| | **Ciprofloxacin** | 500 mg BD | 5–7 days | First-line in India; good tissue penetration; oral bioavailable | | Azithromycin | 500 mg daily | 5–7 days | Alternative; used in fluoroquinolone-resistant strains | | Erythromycin | 500 mg QID | 5–7 days | Older agent; less preferred now | | Gentamicin | IV/IM | Reserved for severe invasive disease | **High-Yield:** Fluoroquinolone resistance in Campylobacter is increasing globally but remains <30% in most Indian settings. Ciprofloxacin is still the empiric choice for non-severe disease in resource-limited settings. **Clinical Pearl:** Early antibiotic therapy (within 3 days) shortens diarrhea duration by ~1 day; late therapy (as in this case at 3 weeks) has limited benefit on symptoms but may reduce bacterial shedding and prevent complications like reactive arthritis or Guillain-Barré syndrome. ## Why Other Options Are Incorrect **Option 1 (Ciprofloxacin) — CORRECT:** Addresses the confirmed diagnosis with evidence-based first-line therapy for prolonged Campylobacter gastroenteritis. --- ## Why Each Distractor Is Wrong