What is a good antibiotic for Shigella in a baby less than 1 year old?

Antibiotic Treatment for Shigella in Infants <1 Year Old

For infants less than 1 year old with shigellosis, azithromycin is the preferred first-line antibiotic, with ceftriaxone as the alternative for severe cases or when azithromycin is not available. 1, 2

First-Line Treatment: Azithromycin

Azithromycin is the preferred antibiotic for shigellosis in infants and children due to its efficacy, safety profile, and favorable dosing schedule. 1, 2, 3

Dosing for Infants

• 10 mg/kg once daily for 3 days (standard regimen) 4, 5
• Alternative: 10 mg/kg on Day 1, then 5 mg/kg daily for Days 2-5 (5-day regimen) 4
• Can be given with or without food 4

Why Azithromycin is Preferred

• Highly effective against Shigella species with documented clinical success rates of 88-95% 1, 5
• Well-tolerated in infants with primarily mild gastrointestinal side effects (diarrhea 3-6%, vomiting 2-6%) 4, 5
• Once-daily dosing improves compliance compared to multiple daily doses 5
• Effective in regions with high fluoroquinolone resistance, which is increasingly common in Asia-Africa (5% resistance to ciprofloxacin, 33.6% to nalidixic acid) 1

Second-Line Treatment: Ceftriaxone

Parenteral ceftriaxone should be used when:

• The infant has severe illness, signs of sepsis, or cannot tolerate oral medications 1, 6
• Local resistance patterns indicate azithromycin resistance 1, 7
• The infant is <3 months old with suspected bacterial dysentery and neurologic involvement 1

Key Points About Ceftriaxone

• Resistance rates remain relatively low (2.5% in Asia-Africa, 0.4% in Europe-America), though increasing after 2007 to 14.2% in some Asian-African regions 1
• Effective as second-line therapy when ciprofloxacin resistance is documented 1
• Typically dosed at 50-100 mg/kg/day (standard pediatric dosing) 6

Alternative Option: Cefixime

Oral cefixime is an appropriate alternative when azithromycin is unavailable or contraindicated, particularly in regions with high ciprofloxacin resistance. 1, 7

• Third-generation cephalosporin with oral bioavailability 7
• Recommended by WHO Working Group as an alternative to azithromycin 1
• Particularly useful when parenteral access is not available 7

Critical Caveats for Infants <1 Year

Avoid Fluoroquinolones in This Age Group

• Ciprofloxacin, while highly effective, is associated with arthropathy risk in children and should generally be avoided in infants <1 year unless no other options exist 1
• The WHO considers shigellosis one of the few indications where fluoroquinolones may be justified in children, but this applies more to older children than infants 1

Avoid First-Generation Agents

• Do not use ampicillin or trimethoprim-sulfamethoxazole as first-line therapy due to widespread resistance (37% of US isolates resistant to both) 7
• High resistance rates globally to ampicillin and cotrimoxazole 1

When to Treat Empirically

Empiric treatment is indicated for infants with: 1

• Bloody diarrhea (dysentery) with fever, abdominal pain, and frequent scant bloody stools (bacillary dysentery pattern presumptively due to Shigella) 1
• Infants <3 months of age with suspected bacterial etiology 1
• Signs of sepsis or severe illness 1

Treatment Duration and Monitoring

• Reassess after 48 hours if no clinical improvement occurs; consider changing antibiotics based on local resistance patterns 1
• Standard treatment duration is 3-5 days depending on the regimen chosen 1, 4
• Rehydration remains the cornerstone of management alongside antibiotics 1

Geographic Considerations

Resistance patterns vary significantly by region: 1

• Asia-Africa regions show higher resistance to fluoroquinolones (5% ciprofloxacin, 33.6% nalidixic acid) and aminoglycosides (10.8% gentamicin) 1
• Europe-America regions have lower resistance rates (0.3% ciprofloxacin, 3.2% nalidixic acid) 1
• Local antibiograms should guide therapy when available, particularly for second-line choices 1