What is the treatment for cellulitis (inflammation of the skin and subcutaneous tissues) with blistering?

Treatment of Cellulitis with Blistering

For cellulitis with blistering, the recommended treatment is an antibiotic active against streptococci, with cephalexin 500 mg orally four times daily for 5-7 days being the first-line therapy for most patients. 1, 2

Antibiotic Selection

First-line options:

• Oral therapy (for typical, uncomplicated cases):
  • Cephalexin 500 mg four times daily
  • Dicloxacillin
  • Amoxicillin
  • Amoxicillin-clavulanate
  • Penicillin
  • Clindamycin (for penicillin-allergic patients)

For severe cases requiring IV therapy:

• Oxacillin
• Nafcillin
• Cefazolin

Treatment Duration

• For uncomplicated cellulitis: 5-7 days is as effective as 10 days if clinical improvement occurs by day 5 1
• For β-hemolytic streptococcal infections: continue for at least 10 days 3

Special Considerations

MRSA Coverage

MRSA is an unusual cause of typical cellulitis. However, consider MRSA coverage in cases with:

• Penetrating trauma
• Illicit drug use history
• Purulent drainage
• Concurrent evidence of MRSA infection elsewhere 1

MRSA treatment options:

• Oral: Clindamycin, trimethoprim-sulfamethoxazole (SMX-TMP), doxycycline
• IV: Vancomycin, daptomycin, linezolid, telavancin

If coverage for both streptococci and MRSA is desired, options include:

• Clindamycin alone (300-450 mg three times daily) 2, 3
• Combination of SMX-TMP or doxycycline with a β-lactam

Clindamycin Dosing

• For serious infections: 150-300 mg every 6 hours
• For more severe infections: 300-450 mg every 6 hours 3
• Take with a full glass of water to avoid esophageal irritation

Management of Blistering

The presence of blistering (bullae) in cellulitis indicates a more severe infection and may warrant:

1. Closer monitoring
2. Consideration of inpatient treatment if accompanied by systemic symptoms
3. Drainage of large bullae using sterile technique
4. Possible extension of treatment duration

When to Consider Hospitalization

• No improvement within 24-48 hours of outpatient treatment
• Presence of severe systemic features (high fever, hypotension, confusion)
• Rapidly spreading infection
• Concern for deeper or necrotizing infection
• Immunocompromised patient 2

Diagnostic Considerations

• Blood cultures are typically unnecessary for typical cases
• Consider blood cultures and tissue cultures for patients with:
  • Malignancy
  • Severe systemic features
  • Unusual predisposing factors (immersion injury, animal bites)
  • Immunodeficiency 1

Common Pitfalls and Caveats

1. Misdiagnosis: Cellulitis can be confused with venous stasis dermatitis, contact dermatitis, deep vein thrombosis, or panniculitis 4, 5

2. Unnecessary MRSA coverage: Despite rising rates of community-acquired MRSA, coverage for non-purulent cellulitis is generally not recommended unless specific risk factors are present 5

3. Treatment failure: Factors associated with treatment failure include:

   • Therapy with an antibiotic not active against the causative organism
   • Greater severity of cellulitis 6

4. Worsening after treatment initiation: Some patients may experience worsening inflammation after starting antibiotics due to pathogen destruction releasing inflammatory mediators 1

5. Inadequate duration: For streptococcal infections, ensure treatment continues for at least 10 days 3

6. Missing necrotizing infection: Always evaluate for signs of deeper infection that would require surgical intervention

By following these guidelines, most cases of cellulitis with blistering can be effectively managed, reducing morbidity and preventing complications.