What is the treatment for Shigella infections?

Treatment for Shigella Infections

The treatment of choice for Shigella infections is antimicrobial therapy with azithromycin (1000 mg as a single dose or 500 mg daily for 3 days) or ciprofloxacin, depending on local susceptibility patterns, along with appropriate rehydration therapy. 1

Diagnostic Approach

Before initiating treatment, confirm the diagnosis through:

• Clinical presentation (bloody diarrhea, abdominal pain, fever, tenesmus)
• Stool examination for white blood cells
• Stool culture (definitive diagnostic method)

Note: If microscopy is unavailable or trophozoites are not seen, patients with bloody diarrhea should be treated initially for shigellosis. 2

Antimicrobial Treatment Options

First-line options (based on local susceptibility patterns):

• Azithromycin: 1000 mg single dose or 500 mg daily for 3 days 1
• Ciprofloxacin: Adult dose of 500 mg twice daily for 3-5 days 2, 1
• TMP-SMX: Adults: 160 mg TMP and 800 mg SMX twice daily for 5 days 2, 3
  • Children: 10 mg/kg/day TMP and 50 mg/kg/day SMX in two divided doses for 5 days 2, 3
• Ampicillin: Adults: 500 mg four times daily for 5 days 2
  • Children: 100 mg/kg/day in four divided doses for 5 days 2

Alternative options (for resistant strains):

• Nalidixic acid: 55 mg/kg/day in four divided doses for 5 days 2
• Tetracycline: 50 mg/kg/day in four divided doses for 5 days 2

Treatment Duration

• Immunocompetent patients: 3-5 days 1
• Immunocompromised patients: 7-10 days 1

Special Considerations

When to Use Empiric Treatment

Empiric antimicrobial therapy is indicated in the following situations:

• Infants < 3 months of age with suspected bacterial etiology
• Immunocompetent patients with fever, abdominal pain, and bloody diarrhea (bacillary dysentery)
• Recent international travelers with fever ≥38.5°C and/or signs of sepsis 2

When to Avoid Antimicrobial Treatment

• Asymptomatic contacts of people with bloody diarrhea should not receive empiric treatment 2
• Mass prophylaxis or prophylaxis of family members is not recommended 2

Rehydration Therapy

• Reduced osmolarity oral rehydration solution (ORS) is recommended as first-line therapy for mild to moderate dehydration 2
• Maintain adequate hydration and nutrition during and after the infection 1, 4

Treatment Modification

• If no clinical response occurs within 2 days, change to another recommended antibiotic 2
• If no improvement after an additional 2 days, refer for stool microscopy to rule out other causes like amebiasis 2
• Antimicrobial therapy should be modified or discontinued when a clinically plausible organism is identified 2

Complications Management

• Monitor for complications such as hemolytic uremic syndrome, reactive arthritis, and toxic megacolon 1
• These complications require specialized management and specific rehabilitation 1

Prevention Strategies

• Hand washing is the single most important strategy for preventing transmission 5, 4
• Proper sanitation, safe water, and food handling practices 1
• Isolation of hospitalized patients and implementation of enteric precautions 1

Important caveat: Due to increasing antimicrobial resistance, periodic susceptibility testing is advisable, especially in endemic and epidemic settings. 2, 1