What is the recommended treatment for Shigella infections?

Treatment of Shigella Infections

Fluoroquinolones are the first-line treatment for Shigella infections, with ciprofloxacin being the preferred agent for 3-7 days. 1

First-line Treatment Options

Adults:

• Ciprofloxacin: 500mg twice daily for 3-7 days (preferred first-line agent) 1
• TMP-SMX: 160mg TMP and 800mg SMX twice daily for 5 days (if susceptible) 1, 2
• Azithromycin: 500mg on day 1, followed by 250mg once daily for 4 days (alternative for resistant strains) 1, 3

Children:

• TMP-SMX: 10mg/kg/day TMP and 50mg/kg/day SMX in two divided doses for 5 days (if susceptible) 1, 2
• Ceftriaxone or cefixime (for resistant strains) 4
• Azithromycin (for resistant strains) 4, 3

Treatment Algorithm

1. Initial treatment selection:

   • Base antibiotic choice on local susceptibility patterns 1
   • For international travel-acquired cases, consider high rates of TMP-SMX resistance 1
   • Fluoroquinolones are preferred first-line when resistance patterns are unknown 1

2. Treatment monitoring:

   • Assess clinical response within 2 days of starting treatment 1
   • If no improvement occurs within 2 days, change to an alternative antibiotic 1

3. For treatment failures:

   • After 2 days of no improvement on second antibiotic, refer for stool microscopy 1
   • Consider resistant shigellosis before considering amebiasis 1

Special Considerations

Resistance Patterns

• Multiresistant strains of Shigella are widespread globally 1, 5, 6
• Resistance to nalidixic acid indicates reduced susceptibility to older fluoroquinolones 7
• Periodic antibiotic susceptibility testing is advisable in endemic and epidemic settings 1

Bacteremia

• For Shigella bacteremia, extend treatment to 14 days using the same agents 1
• Treatment failure is defined by lack of clinical improvement and persistent organisms in stool or blood 1

HIV-Infected Patients

• All HIV-associated Shigella infections should be treated due to higher risk of complications 1
• HIV-infected persons have higher rates of adverse effects related to TMP-SMX 1

Common Pitfalls and Caveats

• Avoid mass prophylaxis: WHO does not recommend mass prophylaxis or prophylaxis of family members as a control measure for shigellosis 1

• Misdiagnosis: Amebic dysentery tends to be misdiagnosed as shigellosis. If two different antibiotics for shigellosis fail to improve symptoms, consider amebiasis 1

• Monitoring: Patients should be monitored closely for response to treatment, defined by improvement in systemic signs and symptoms and resolution of diarrhea 1

• Follow-up cultures: Generally not required if complete clinical response has been demonstrated, except for food service workers or healthcare workers 1