What is the treatment for Shigellosis?

Treatment of Shigellosis

The first-line treatment for shigellosis in adults is ciprofloxacin 500mg twice daily for 3-7 days, while children should receive either azithromycin or a third-generation cephalosporin based on local susceptibility patterns. 1, 2

Antimicrobial Treatment Options

First-line Treatment for Adults:

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

First-line Treatment for Children:

• TMP-SMX 10mg/kg/day TMP and 50mg/kg/day SMX in two divided doses for 5 days (if strain is susceptible) 3, 1
• Third-generation cephalosporin for infants <3 months of age and those with neurologic involvement 3
• Azithromycin based on local susceptibility patterns 3, 1

Alternative Options (for resistant strains):

• Nalidixic acid 55mg/kg/day in four divided doses for 5 days 3
• Tetracycline 50mg/kg/day in four divided doses for 5 days 3

Treatment Algorithm

1. Initial Assessment:

   • Confirm diagnosis through clinical presentation (bloody diarrhea, abdominal cramps, tenesmus) 3
   • Collect stool sample for culture and susceptibility testing before starting antibiotics 3

2. Initial Antibiotic Selection:

   • Base choice on local susceptibility patterns 1
   • For travel-acquired cases, consider high rates of TMP-SMX resistance 1
   • Use fluoroquinolones as first-line when resistance patterns are unknown 1

3. Monitoring Response:

   • Assess clinical response within 2 days of starting treatment 3, 1
   • If no improvement occurs within 2 days, change to an alternative antibiotic 3, 1
   • If no improvement after an additional 2 days with second antibiotic, consider alternative diagnoses such as amebiasis 3

4. Special Situations:

   • For Shigella bacteremia, extend treatment to 14 days 1
   • All HIV-associated Shigella infections should be treated due to higher risk of complications 1

Supportive Care

• Rehydration therapy with reduced osmolarity oral rehydration solution (ORS) for mild to moderate dehydration 3
• Monitor fluid and electrolyte balance, especially in severe cases 3
• Nutritional support during recovery phase 3

Common Pitfalls and Caveats

• Multiresistant strains of Shigella are widespread globally, necessitating periodic antibiotic susceptibility testing in endemic and epidemic settings 3, 1
• Amebic dysentery is commonly misdiagnosed as shigellosis - consider this diagnosis if two different antibiotics fail to improve symptoms 3
• The WHO does not recommend mass prophylaxis or prophylaxis of family members as a control measure for shigellosis 3
• Single-dose ciprofloxacin therapy is effective for species other than S. dysenteriae type 1, but insufficient for S. dysenteriae type 1 infections 4
• HIV-infected persons have higher rates of adverse effects related to TMP-SMX 1
• Follow-up cultures are generally not required if complete clinical response has been demonstrated, except for food service workers or healthcare workers 1

Emerging Treatment Considerations

• Fluoroquinolone-resistant S. dysenteriae type 1 infections have been reported, requiring vigilance in treatment selection 5
• Azithromycin has shown efficacy against multidrug-resistant Shigella strains, even when serum concentrations only equal the minimum inhibitory concentration of the infecting strain 6
• The American Academy of Pediatrics recommends cefixime, ceftriaxone, azithromycin, and fluoroquinolones as alternative antibiotics for treating Shigella infections in children when first-line agents fail 7