What is the recommended treatment for cellulitis?

Treatment of Cellulitis

For uncomplicated cellulitis, the recommended first-line treatment is a 5-day course of an antibiotic active against streptococci, such as cephalexin 500 mg 3-4 times daily or clindamycin 300-450 mg three times daily. 1, 2

Antibiotic Selection Algorithm

Mild Cellulitis (No Systemic Signs)

• First-line options:
  • Cephalexin 500 mg orally 3-4 times daily for 5 days
  • Clindamycin 300-450 mg orally three times daily for 5 days
  • Amoxicillin-clavulanate 875/125 mg orally twice daily for 5 days 1, 2

Moderate Cellulitis (With Systemic Signs)

• Recommended regimens:
  • Coverage for streptococci plus consideration for MSSA
  • Cephalexin 500 mg orally 4 times daily for 5 days
  • If penicillin allergic: Clindamycin 300-450 mg orally three times daily for 5 days 1

Severe Cellulitis or High-Risk for MRSA

• Indications for MRSA coverage:

  • Penetrating trauma
  • Evidence of MRSA infection elsewhere
  • MRSA nasal colonization
  • Injection drug use
  • Systemic inflammatory response syndrome (SIRS)
  • Prior MRSA infection
  • Recent hospitalization
  • Antibiotic use in past 3 months 1, 2

• Treatment options:

  • Vancomycin (IV dosing based on weight)
  • For severely compromised patients: Vancomycin plus piperacillin-tazobactam or imipenem/meropenem 1

Duration of Therapy

• Standard duration: 5 days
• Extend treatment if infection has not improved within this time period 1

Adjunctive Measures

• Elevation of the affected area to reduce edema 1, 2
• Treatment of predisposing factors (edema, underlying skin disorders) 1
• For lower extremity cellulitis: Careful examination and treatment of interdigital toe spaces to eradicate colonization with pathogens 1

Hospitalization Criteria

Admit patients with:

• SIRS
• Altered mental status
• Hemodynamic instability
• Concern for deeper or necrotizing infection
• Poor adherence to therapy
• Severe immunocompromise
• Failure of outpatient treatment 1, 2

Prevention of Recurrence

For patients with 3-4 episodes per year despite treatment of predisposing factors:

• Oral penicillin or erythromycin twice daily for 4-52 weeks, or
• Intramuscular benzathine penicillin every 2-4 weeks 1, 2

Diagnostic Considerations

• Blood cultures are not routinely recommended for typical cases
• Consider cultures of blood or cutaneous aspirates/biopsies in patients with:
  • Malignancy on chemotherapy
  • Neutropenia
  • Severe cell-mediated immunodeficiency
  • Immersion injuries
  • Animal bites 1

Corticosteroid Consideration

• Systemic corticosteroids (prednisone 40 mg daily for 7 days) could be considered in non-diabetic adult patients with cellulitis 1

Common Pitfalls

1. Misdiagnosis: Venous insufficiency, eczema, deep vein thrombosis, and gout are frequently mistaken for cellulitis 3
2. Inadequate treatment duration: Extend treatment if not improving after 5 days 1
3. Failure to address predisposing factors: Treating underlying conditions is essential to prevent recurrence 1, 3
4. Missing atypical pathogens: Consider less common organisms when standard treatment fails 4
5. Overlooking necrotizing infections: Carefully assess for signs of deeper infection requiring surgical intervention 5

The Infectious Diseases Society of America guidelines provide the most comprehensive recommendations for cellulitis management, emphasizing targeted antibiotic therapy based on severity and risk factors, with appropriate duration and adjunctive measures to improve outcomes and prevent recurrence.