Treatment for Shigella
The first-line antimicrobial treatment for shigellosis should be based on local antibiotic susceptibility patterns, with azithromycin or ciprofloxacin as preferred empiric choices in adults, and azithromycin or ceftriaxone in children, while avoiding fluoroquinolones in children and pregnant women. 1
Initial Approach and Diagnosis
When a patient presents with bloody diarrhea, treat empirically for shigellosis if microscopy is unavailable or if amebic trophozoites are not definitively identified 2. Antimicrobial therapy decreases the severity and duration of dysentery and reduces pathogen excretion 2.
First-Line Antimicrobial Therapy
Adults
- Azithromycin (preferred first-line) 1
- Ciprofloxacin (alternative first-line) 1
- Critical caveat: Avoid fluoroquinolones if ciprofloxacin MIC ≥0.12 μg/mL, even if reported as susceptible 1
- TMP-SMX: 160 mg TMP/800 mg SMX twice daily for 5 days (if susceptible) 2
- Ampicillin: 500 mg four times daily for 5 days (if susceptible) 2
Children
- Azithromycin (preferred) 1
- Ceftriaxone (alternative) 1
- TMP-SMX: 10 mg/kg/day TMP and 50 mg/kg/day SMX in two divided doses for 5 days (if susceptible) 2
- Ampicillin: 100 mg/kg/day in four divided doses for 5 days (if susceptible) 2
Pregnant and Lactating Women
Fluoroquinolones are not approved for use in pregnant or lactating women 2. Consider:
- Azithromycin (preferred)
- Ceftriaxone
- TMP-SMX or ampicillin if susceptible
Second-Line Options for Resistant Strains
If no clinical response occurs within 2 days, switch to an alternative antibiotic 2:
- 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
- Cefixime: Reasonable alternative, though weigh against risk of ESBL dissemination 3
If no improvement after an additional 2 days of the second antibiotic, refer for hospital evaluation and stool microscopy 2. At this stage, resistant shigellosis remains more likely than amebiasis 2.
Critical Resistance Considerations
Multiresistant Shigella strains are widespread globally 2. The choice of empiric therapy must be guided by:
- Local/regional antibiotic susceptibility patterns 2
- Periodic susceptibility testing by reference laboratories 2
- Approximately 37% of U.S. isolates show resistance to both ampicillin and TMP-SMX 4
- Fluoroquinolone resistance and azithromycin non-susceptibility are ongoing threats 5
Special Populations and Situations
Severe Shigella dysenteriae Type 1 Infections
- Single-dose ciprofloxacin (1 gram) is inferior to 5-day therapy for S. dysenteriae type 1 6
- Use standard 5-day courses for this species
- Single-dose therapy is effective for other Shigella species 6
Post-Antibiotic Exposure
- Patients who received antibiotics prior to presentation are universally culture-negative 7
- Molecular diagnostics (qPCR) can still detect Shigella in 30% of these cases 7
High-Risk Groups
- Men who have sex with men (MSM) and people living with HIV show increased incidence 8, 5
- Avoid sexual contact during illness and for 1-2 weeks after symptom resolution 8
What NOT to Do
- Do not use mass prophylaxis or prophylaxis of family members—WHO does not recommend this 2
- Do not prescribe fluoroquinolones if ciprofloxacin MIC ≥0.12 μg/mL 1
- Do not use fluoroquinolones in children or pregnant/lactating women 2
- Do not treat for amebiasis unless microscopy shows definite trophozoites or two different antibiotics for shigellosis have failed 2
Supportive Care
While the guidelines emphasize antimicrobial therapy, ensure:
- Rehydration therapy if dehydration is present 9
- Appropriate feeding during and after the episode 9
- Hand-washing as the single most important prevention strategy 9
Monitoring Treatment Response
Assess clinical response at 48 hours 2. If symptoms worsen or persist: