What antibiotics are used to treat skin infections?

Antibiotics for Skin Infections

For mild skin infections, first-line antibiotics include amoxicillin-clavulanic acid, cloxacillin, or cefalexin, while severe infections require combination therapy such as clindamycin plus piperacillin-tazobactam or ceftriaxone plus metronidazole, with vancomycin added for suspected MRSA. 1

Classification and First-Line Treatment

Mild to Moderate Skin Infections

• First-choice antibiotics (per WHO guidelines):

  • Amoxicillin-clavulanic acid
  • Cloxacillin (or other anti-staphylococcal penicillins)
  • Cefalexin 1

• For mild purulent infections (e.g., small abscesses):

  • Incision and drainage is primary treatment
  • Oral antibiotics if systemic symptoms present:
    • TMP-SMX (trimethoprim-sulfamethoxazole)
    • Doxycycline
    • Clindamycin 1

• For mild non-purulent infections (e.g., cellulitis, erysipelas):

  • Cephalexin 500mg 3-4 times daily for 5-6 days
  • Clindamycin 300-450mg three times daily for 5-6 days (if penicillin allergic)
  • Amoxicillin-clavulanate 875/125mg twice daily for 5-6 days 2

Severe Skin Infections

• Necrotizing fasciitis requires aggressive treatment:

  • Clindamycin plus piperacillin-tazobactam (with or without vancomycin)
  • Alternative: ceftriaxone plus metronidazole (with or without vancomycin) 1

• For severe purulent infections:

  • Vancomycin IV
  • Linezolid
  • Daptomycin
  • Ceftaroline 1

Pathogen-Specific Treatment

Staphylococcus aureus

• MSSA (Methicillin-Susceptible S. aureus):

  • First-line: Dicloxacillin or cephalexin 1
  • Alternative: Clindamycin or TMP-SMX 3

• MRSA (Methicillin-Resistant S. aureus):

  • Mild infections: TMP-SMX, doxycycline, or clindamycin 1
  • Severe infections: Vancomycin IV (first-line), linezolid, or daptomycin 3, 4

Streptococcal Infections

• Group A Streptococcus:
  • First-line: Penicillin (for isolated streptococcal infections)
  • Alternative: Cephalexin or clindamycin 1
  • For impetigo/ecthyma: 7-day regimen with anti-staphylococcal agent 1

Special Considerations

Diabetic Wound Infections

• Mild infections: Dicloxacillin, clindamycin, cefalexin, levofloxacin, amoxicillin-clavulanic acid, or doxycycline
• Moderate to severe infections: Levofloxacin, cefoxitin, ceftriaxone, ampicillin-sulbactam, or ertapenem
• For suspected MRSA: Add TMP-SMX, linezolid, daptomycin, or vancomycin 1

Periorbital Cellulitis

• Mild cases: Oral antibiotics (outpatient)
• Moderate to severe: IV antibiotics (hospitalization)
  • First-line: Vancomycin 15-20 mg/kg IV every 8-12 hours
  • Alternatives: Daptomycin, linezolid, or clindamycin 2

Pediatric Dosing

For cefalexin in pediatric patients:

• Usual recommended daily dosage: 25-50 mg/kg in divided doses
• For skin infections: Total daily dose may be divided and administered every 12 hours 5

Treatment Duration

• Standard duration for most skin infections: 5-6 days 2
• For streptococcal pharyngitis/tonsillitis: 10 days to prevent rheumatic fever 1
• Monitor for improvement within 72 hours; if no improvement, reevaluate treatment plan 2

Pitfalls and Caveats

1. Increasing antibiotic resistance: Always consider local resistance patterns when selecting empiric therapy
2. Drainage is crucial: For abscesses, surgical drainage is the primary intervention; antibiotics alone are often insufficient
3. MRSA consideration: In areas with high MRSA prevalence, empiric coverage should include MRSA-active agents
4. Deeper infection signs: Watch for systemic symptoms, bullae, skin sloughing, or hypotension that suggest more severe infection requiring aggressive treatment
5. Supportive care: Don't forget elevation of affected limbs, warm compresses, and adequate pain control 2

Remember to reassess therapy after culture results become available and adjust antibiotics accordingly to prevent development of resistance.