What is the recommended treatment for Shigella infections?

Treatment of Shigella Infections

Fluoroquinolones are the first-line treatment for Shigella infections in adults, while azithromycin is preferred for children due to concerns about arthropathy with fluoroquinolones. 1

Adult Treatment Options

First-line Treatment

• Ciprofloxacin: 500 mg twice daily for 3-7 days 1
  • Most effective option with high cure rates
  • Concentrations exceed the minimum inhibitory concentration (MIC) by 28 times 2

Alternative Options (if resistance or contraindications to fluoroquinolones)

• Trimethoprim-sulfamethoxazole (TMP-SMX): 160 mg TMP and 800 mg SMX twice daily for 5 days 3, 4
  • FDA-approved for shigellosis 4
  • High resistance rates in many regions (up to 89% in some studies) 5
• Azithromycin: 500 mg on day 1, followed by 250 mg once daily for 4 days 2
  • Clinical success rate of 82% compared to 89% with ciprofloxacin 2
• Nalidixic acid: 55 mg/kg/day in four divided doses for 5 days 3
• Tetracycline: 50 mg/kg/day in four divided doses for 5 days 3

Pediatric Treatment Options

First-line Treatment

• Azithromycin: 10 mg/kg on day 1, followed by 5 mg/kg once daily for 4 days 1
  • Preferred for children due to safety profile
  • Lower resistance rates in some regions (7%) 5

Alternative Options

• TMP-SMX: 10 mg/kg/day TMP and 50 mg/kg/day SMX in two divided doses for 5 days 3, 4
  • For children ≥2 months of age 4
  • High resistance rates limit usefulness
• Ceftriaxone: Consider when other options aren't available 5
  • Increasing resistance (up to 51% in some studies) 5

Treatment Algorithm

1. Assess patient age and severity:

   • Mild cases in healthy adults may resolve without antibiotics
   • Moderate to severe cases require antibiotic therapy

2. Consider local resistance patterns:

   • Periodic antibiotic susceptibility testing is advisable 3
   • Resistance to ampicillin and TMP-SMX is widespread 5
   • Fluoroquinolone resistance is increasing but still relatively low (1.5-7%) 5, 6

3. Monitor treatment response:

   • If no clinical response occurs within 2 days, change to another recommended antibiotic 3
   • If no improvement after an additional 2 days, refer for stool microscopy 3

Special Considerations

• Immunocompromised patients: May require extended treatment for up to 14 days 1
• Bacteremia: May require extended treatment for up to 14 days 1
• Food handlers/healthcare workers: May require follow-up stool culture to ensure clearance 1

Common Pitfalls and Caveats

1. Resistance development: Multiresistant strains of Shigella are widespread globally 3, 7

   • In vitro studies suggest azithromycin and ceftriaxone may promote resistance 7
   • Fluoroquinolones remain effective against wild-type strains but may select for resistance in strains with pre-existing gyrA mutations 7

2. Prophylaxis: WHO does not recommend mass prophylaxis or prophylaxis of family members as a control measure for shigellosis 3

3. Treatment failure: Consider:

   • Antimicrobial resistance
   • Alternative diagnoses (amebiasis, giardiasis)
   • Complications (bacteremia, intestinal perforation)

4. Regional variations: Resistance patterns vary significantly by region

   • In Iran, ciprofloxacin remains effective (resistance <7%) while ceftriaxone and azithromycin show higher resistance rates 6
   • Always consider local epidemiology when selecting empiric therapy

By following this evidence-based approach to treating Shigella infections, clinicians can optimize outcomes while minimizing the risk of treatment failure and antimicrobial resistance.