What is the drug of choice for treating bacillary dysentery in adults and children?

Drug of Choice for Bacillary Dysentery

Azithromycin is the drug of choice for treating bacillary dysentery in both adults and children, given as a single 1000 mg dose or 500 mg daily for 3 days in adults, and 10 mg/kg on day 1 followed by 5 mg/kg daily for 4 days in children. 1, 2

Rationale for Azithromycin as First-Line

Azithromycin has replaced fluoroquinolones as the preferred agent due to widespread fluoroquinolone resistance, which now exceeds 85-90% for Campylobacter species in Southeast Asia and reaches significant levels globally for Shigella species. 1, 2 The American College of Travel Medicine and WHO both recommend azithromycin as first-line therapy for dysentery regardless of geographic region because it provides superior coverage against the most common invasive pathogens causing bloody diarrhea. 1, 2

Key Efficacy Data

• For Campylobacter infections: Azithromycin achieves 100% clinical and bacteriological cure rates, far superior to fluoroquinolones which have documented treatment failures. 1
• For Shigella infections: Azithromycin demonstrates effective and comparable cure rates to other agents while avoiding resistance issues. 1
• Broader spectrum: Effective against enteroinvasive E. coli, Aeromonas spp., Plesiomonas spp., and Yersinia enterocolitica. 1

Dosing Regimens

Adults

• Preferred: Single 1000 mg oral dose (superior adherence and convenience with equivalent efficacy) 1
• Alternative: 500 mg orally daily for 3 days 1
• Severe cases requiring IV therapy: 500 mg IV daily for 2-5 days, followed by oral therapy if needed 1

Children

• 10 mg/kg on day 1, followed by 5 mg/kg daily for 4 days 2
• Single-dose regimens of 1000 mg may be considered for mild to moderate cases in older children to improve compliance 2

When to Treat Empirically

Empiric antibiotic therapy is indicated for: 2

• Infants < 3 months of age with bloody diarrhea and suspected bacterial etiology
• Children with fever, abdominal pain, bloody diarrhea, and presumptive bacillary dysentery
• Patients with recent international travel, body temperature ≥38.5°C, and/or signs of sepsis
• Immunocompromised patients with severe illness and bloody diarrhea

Alternative Agents (When Azithromycin Unavailable or Contraindicated)

Second-Line Options

• Ciprofloxacin: 15 mg/kg per dose orally in children (despite arthropathy concerns), or 1 g single dose in adults 2, 3, 4

  • Critical limitation: Resistance rates are high and increasing, making this less reliable 1, 2
  • May still be effective in regions with lower resistance patterns 5

• Cefixime: Appropriate alternative when fluoroquinolone resistance is high, effective against shigellosis 2

• Ceftriaxone: For severe illness, immunocompromised patients, or infants < 3 months with neurologic involvement (resistance rates only 2.5% in Asia-Africa) 2

Older Agents (Generally No Longer Recommended)

• Tetracycline, ampicillin, and co-trimoxazole were previously effective but are now largely ineffective due to widespread resistance 3, 6

Critical Pitfalls to Avoid

Do not use rifaximin for dysentery - it has documented treatment failures in up to 50% of cases with invasive pathogens and should specifically not be prescribed when Campylobacter, Shigella, or other invasive organisms are suspected. 1, 2

Do not use fluoroquinolones as first-line - they are inferior to azithromycin for Shigella and have high failure rates for fluoroquinolone-resistant Campylobacter. 1

Avoid antimotility agents (such as loperamide) in patients with acute dysentery, as they are contraindicated. 2, 3

Do not treat STEC O157 or other Shiga toxin-producing E. coli with antibiotics, as this increases risk of hemolytic uremic syndrome. 2

Do not administer azithromycin simultaneously with aluminum or magnesium-containing antacids, as they reduce absorption. 2

Treatment Duration and Monitoring

• 3-5 days of treatment is typically sufficient for uncomplicated cases 2
• If no clinical response occurs within 48 hours, consider resistant Shigella or alternative diagnoses and switch to an alternative agent 1, 2
• Monitor for gastrointestinal side effects (occur in approximately 3-4% of patients) 2

Adjunctive Management

• Oral rehydration salt should be given concurrently to prevent or correct dehydration 3
• Continue feeding during and after shigellosis 3
• Hand-washing practices with soap and water help prevent person-to-person transmission 3

Geographic Considerations

In Southeast Asia and India, azithromycin should be the default empiric agent for any dysentery due to extremely high fluoroquinolone resistance rates (78-93% for Campylobacter). 1 Even in other geographic regions, azithromycin remains preferred because invasive pathogens are likely when dysentery is present. 1