What is the most appropriate antibiotic and dosage for a 28kg child with an infected cut on the bottom of the foot?

Antibiotic Treatment for Infected Foot Cut in a 28kg Child

For a 28kg child with an infected cut on the bottom of the foot, cephalexin at a dose of 25-50 mg/kg/day divided into 4 doses (approximately 175-350 mg four times daily) is the most appropriate first-line antibiotic therapy. 1

First-Line Treatment Options

Beta-lactam antibiotics

• Cephalexin: 25-50 mg/kg/day in 4 divided doses (175-350 mg four times daily)

  • First-line oral agent for uncomplicated skin and soft tissue infections
  • Effective against methicillin-susceptible Staphylococcus aureus (MSSA) and Streptococcus species
  • Suitable for penicillin-allergic patients except those with immediate hypersensitivity reactions
  • Available as suspension, making it practical for pediatric use 1

• Dicloxacillin: 25-50 mg/kg/day in 4 divided doses

  • Alternative oral agent for MSSA
  • Less commonly used in pediatrics 1

Alternative Options (if MRSA is suspected or confirmed)

If community-acquired methicillin-resistant S. aureus (CA-MRSA) is suspected based on local prevalence patterns or previous history:

• Clindamycin: 30-40 mg/kg/day in 3 divided doses (approximately 280-370 mg three times daily)

  • Important option for children with suspected MRSA
  • Caution: potential for cross-resistance in erythromycin-resistant strains 1

• Trimethoprim-sulfamethoxazole (TMP-SMX): 8-12 mg/kg/day based on trimethoprim component in 2 divided doses

  • Effective against MRSA
  • Note: Less effective for streptococcal infections, which may be present in foot wounds 2

Treatment Duration

• Treatment duration should be approximately 7 days, depending on clinical response 1
• For deeper or more severe infections, longer courses may be necessary

Assessment Factors to Consider

When evaluating the infected foot wound:

1. Severity of infection:

   • Presence of surrounding erythema, warmth, tenderness
   • Extent of cellulitis beyond the wound
   • Presence of purulent drainage

2. Risk factors for MRSA:

   • Local prevalence of MRSA
   • Previous MRSA infections
   • Recent antibiotic use

3. Location considerations:

   • Foot wounds may have higher risk of gram-negative and polymicrobial infections
   • Consider broader coverage if deeper infection is suspected

Important Caveats

• Drainage: If abscess formation is present, incision and drainage is essential for treatment success 3
• MRSA consideration: In areas with high MRSA prevalence, consider MRSA coverage if the infection appears more severe or fails to respond to initial beta-lactam therapy
• Monitoring: Re-evaluate within 48-72 hours to ensure appropriate response to therapy
• Tetracyclines: Doxycycline is not recommended for children under 8 years of age 1
• Foot location: The plantar surface of the foot may be subject to more contamination and different bacterial profiles than other skin locations

Treatment Failure

If no improvement after 48-72 hours of initial therapy:

1. Consider wound culture and sensitivity testing
2. Reassess need for drainage procedure
3. Consider switching to alternative antibiotic with different coverage spectrum
4. Evaluate for deeper infection requiring more aggressive management

Beta-lactams remain appropriate first-line therapy even in regions with endemic CA-MRSA for uncomplicated skin infections 2, but close follow-up is essential to identify treatment failures early.