What is the treatment for shigella enteritis?

Treatment of Shigella Enteritis

For suspected or confirmed Shigella enteritis with bacillary dysentery (fever, bloody diarrhea, abdominal cramps, tenesmus), empiric antibiotic therapy should be initiated with either a fluoroquinolone (ciprofloxacin 500mg twice daily for adults) or azithromycin (500mg day 1, then 250mg daily for 4 days), based on local resistance patterns and travel history. 1, 2

When to Treat Empirically

Antibiotic treatment is indicated for:

• Ill immunocompetent patients with documented fever, abdominal pain, bloody diarrhea, and clinical bacillary dysentery (frequent scant bloody stools, fever, abdominal cramps, tenesmus) presumptively due to Shigella 1
• Infants <3 months of age with suspected bacterial etiology 1
• Recent international travelers with body temperature ≥38.5°C and/or signs of sepsis 1
• Immunocompromised patients with severe illness and bloody diarrhea 1

Do not treat empirically in most immunocompetent adults and children with bloody diarrhea while awaiting diagnostic results, unless meeting above criteria 1

First-Line Antibiotic Regimens

Adults

Fluoroquinolones (preferred when resistance patterns unknown):

• Ciprofloxacin 500mg twice daily for 3-7 days 2, 3
• Alternative fluoroquinolones include ofloxacin 1

Azithromycin (for resistant strains or when fluoroquinolones contraindicated):

• 500mg on day 1, followed by 250mg once daily for 4 days 2

TMP-SMX (if strain is susceptible):

• 160mg TMP and 800mg SMX (1 double-strength tablet) twice daily for 5 days 1, 2, 4

Children

Azithromycin (preferred):

• Dosing based on local susceptibility patterns and travel history 1

Third-generation cephalosporin:

• For infants <3 months or those with neurologic involvement 1

TMP-SMX (if strain is susceptible):

• 10mg/kg/day TMP and 50mg/kg/day SMX in two divided doses for 5 days 1, 2, 4

Alternative regimens for resistant strains:

• Nalidixic acid: 55mg/kg/day in four divided doses for 5 days 1
• Tetracycline: 50mg/kg/day in four divided doses for 5 days (avoid in young children) 1

Treatment Algorithm and Monitoring

Initial antibiotic selection must be based on:

• Local susceptibility patterns (most critical factor) 1, 2
• Travel history (consider high TMP-SMX resistance in international travel-acquired cases) 2
• Patient age and immune status 1

Clinical response assessment:

• Evaluate clinical improvement within 2 days of starting treatment 1, 2
• If no clinical response within 2 days, change to an alternative antibiotic 1, 2
• If no improvement after an additional 2 days with second antibiotic, refer for stool microscopy to rule out amebiasis 1

Modify treatment when organism identified:

• Antimicrobial therapy should be modified or discontinued when a clinically plausible organism is identified and susceptibility results are available 1

Critical Resistance Considerations

Multiresistant Shigella strains are widespread globally 1, 2, 5

• Shigella strains can rapidly acquire resistance in endemic and epidemic settings 1
• Periodic antibiotic susceptibility testing by a reference laboratory is advisable 1, 2
• Fluoroquinolones are preferred first-line when resistance patterns are unknown 2
• TMP-SMX resistance is particularly high in travel-acquired cases 2

Supportive Care

Rehydration is essential:

• Reduced osmolarity oral rehydration solution (ORS) is first-line therapy for mild to moderate dehydration 1
• Concurrent ORS administration prevents or corrects dehydration 6

Antimotility agents are contraindicated 6

Feeding should be continued during and after illness 1, 6

Common Pitfalls and Caveats

Amebic dysentery is frequently misdiagnosed as shigellosis:

• If two different antibiotics for shigellosis fail to improve symptoms, consider amebiasis 1, 2
• Stool microscopy should identify Entamoeba histolytica trophozoites (distinguish from white blood cells) 1
• Treat with metronidazole if amebiasis confirmed: adults 750mg three times daily for 5-10 days; children 30mg/kg/day for 5-10 days 1

Mass prophylaxis is not recommended:

• WHO does not recommend mass prophylaxis or prophylaxis of family members as a control measure 1, 2
• Asymptomatic contacts should not receive empiric treatment but should follow infection prevention measures 1

Special populations require extended treatment:

• Shigella bacteremia requires 14 days of treatment using the same agents 2
• All HIV-associated Shigella infections should be treated due to higher complication risk 2
• HIV-infected persons have higher rates of adverse effects with TMP-SMX 2

Follow-up cultures:

• Generally not required if complete clinical response demonstrated 2
• Required for food service workers or healthcare workers before return to work 1