What is the appropriate treatment for a skin infection?

Treatment of Skin Infections

The appropriate treatment for skin infections depends on the type and severity of infection, with first-line therapy for uncomplicated skin infections being oral cephalexin for non-purulent infections and incision and drainage plus antimicrobial therapy for purulent infections. 1

Classification and Initial Assessment

Skin infections can be broadly categorized into:

1. Non-purulent infections (cellulitis, erysipelas)
2. Purulent infections (abscesses, furuncles, carbuncles)
3. Necrotizing infections (fasciitis, myonecrosis)

Key Assessment Factors:

• Extent of erythema and induration
• Presence of purulence
• Systemic symptoms (fever >38.5°C, tachycardia >110 beats/min)
• Immunocompromised status
• Location of infection (face, hand, perineum)

Treatment Algorithm

1. Non-purulent Infections (Cellulitis, Erysipelas)

• Mild infection (limited area, no systemic symptoms):

  • First-line: Cephalexin 500 mg orally 4 times daily for 5-7 days 1, 2
  • Alternative: Dicloxacillin, clindamycin, or amoxicillin-clavulanate

• Moderate infection (more extensive or systemic symptoms):

  • First-line: Cephalexin 500 mg orally 4 times daily for 7-10 days
  • If MRSA suspected: Add trimethoprim-sulfamethoxazole or switch to clindamycin

• Severe infection (extensive area, significant systemic symptoms):

  • Hospitalization with IV antibiotics: Vancomycin, linezolid, or daptomycin 1

2. Purulent Infections (Abscesses, Furuncles)

• Primary treatment: Incision and drainage 3

• Adjunctive antibiotics (for any of these conditions):

  • Extensive surrounding cellulitis
  • Systemic symptoms
  • Immunocompromised host
  • Extremes of age
  • Infection in critical area (face, hand, genitalia)

• Antibiotic choices:

  • MSSA coverage: Cephalexin 500 mg orally 4 times daily 1
  • MRSA coverage: Trimethoprim-sulfamethoxazole, doxycycline, or clindamycin 3

3. Necrotizing Infections

• Immediate surgical consultation for debridement 1
• Empiric broad-spectrum antibiotics:
  • Vancomycin plus piperacillin-tazobactam or a carbapenem 1
  • For documented group A streptococcal infection: Penicillin plus clindamycin 1

Special Considerations

Impetigo

• Limited lesions: Topical mupirocin ointment applied 3 times daily for 5-7 days 1, 4
• Widespread lesions: Oral cephalexin or other anti-staphylococcal/streptococcal agent 1

Pediatric Dosing

• Cephalexin: 25-50 mg/kg/day divided in 4 doses 2
• For otitis media: 75-100 mg/kg/day in 4 divided doses 2

Immunocompromised Patients

• Lower threshold for hospitalization and IV antibiotics
• Consider broader coverage including gram-negative and anaerobic organisms 1

Animal or Human Bites

• Amoxicillin-clavulanate is the drug of choice 1
• For penicillin-allergic patients: Clindamycin plus either ciprofloxacin or trimethoprim-sulfamethoxazole 1

Common Pitfalls and Caveats

1. Failure to drain purulent collections: Antibiotics alone are often insufficient for abscesses 3

2. Inappropriate antibiotic selection: Consider local resistance patterns, especially for MRSA

3. Inadequate duration: For streptococcal pharyngitis and skin infections, a full 10-day course is recommended 1

4. Missing necrotizing infections: Watch for:

   • Pain out of proportion to physical findings
   • Rapid progression
   • Crepitus or gas in tissues
   • Systemic toxicity
   • Skin necrosis or bullae 1

5. Overuse of broad-spectrum antibiotics: Reserve vancomycin and newer agents for severe infections or confirmed MRSA 1

6. Failure to reassess: Patients should be reevaluated within 48-72 hours to ensure appropriate response 3

Cephalexin has maintained excellent efficacy against streptococcal and susceptible staphylococcal skin infections for decades, with cure rates of 90% or higher 5. For more severe infections requiring hospitalization, following the IDSA guidelines for appropriate empiric therapy is crucial to reduce morbidity and mortality.