What is the treatment for cellulitis?

Treatment of Cellulitis

For non-purulent cellulitis, beta-lactam antibiotics are the first-line treatment, while purulent cellulitis requires coverage for CA-MRSA with clindamycin 600 mg orally three times daily for 5-10 days. 1

Diagnosis and Classification

Before initiating treatment, it's important to classify cellulitis properly:

• Non-purulent cellulitis: No drainage or exudate, typically caused by beta-hemolytic streptococci
• Purulent cellulitis: With drainage/exudate, may involve Staphylococcus aureus (including MRSA)

Look for signs of deeper infection or necrotizing fasciitis such as severe pain, rapid progression, crepitus, and systemic toxicity that would require immediate hospitalization 1.

Antibiotic Treatment Algorithm

First-line Treatment Options:

1. For non-purulent cellulitis:

   • Beta-lactam antibiotics (recommended by IDSA) 1
   • Dicloxacillin 250 mg orally every 6 hours (adults) 2
   • Amoxicillin-clavulanate (Augmentin) for toe cellulitis with mixed infections 1

2. For purulent cellulitis:

   • Clindamycin 600 mg orally three times daily 1, 3
   • Alternative options:
     • TMP-SMX plus a beta-lactam (e.g., amoxicillin)
     • Doxycycline (not for children <8 years)
     • Linezolid 600 mg twice daily 1

Treatment Duration:

• Standard duration: 5-10 days 1
• 5 days is as effective as 10 days for uncomplicated cases 1
• For β-hemolytic streptococcal infections, continue for at least 10 days 3
• For severe staphylococcal infections, therapy should continue for at least 14 days 2

Severe Cases:

• Intravenous antibiotics are recommended for severe cases or when oral antibiotics fail:
  • Cefazolin 0.5-1 g every 8 hours or
  • Oxacillin or nafcillin 2 g every 6 hours 1
  • Consider vancomycin for MRSA coverage in severe cases 1

Additional Management

Wound Care:

• Obtain cultures from infected wounds to guide therapy 1
• Consider incision and drainage if abscess formation is present 1
• Keep draining wounds covered with clean, dry bandages 1
• Elevate the affected area to promote drainage of edema 1

Special Considerations:

• Take dicloxacillin on an empty stomach (1 hour before or 2 hours after meals) with at least 120 mL of water 2
• Take clindamycin with a full glass of water to avoid esophageal irritation 3
• Discontinue clindamycin if significant diarrhea occurs due to risk of C. difficile infection 3
• Avoid using TMP-SMX alone for non-purulent cellulitis due to poor activity against streptococci 1
• Tetracyclines should not be used in children under 8 years of age 1

Prevention of Recurrence

For patients with recurrent cellulitis:

• Treat underlying conditions: tinea pedis, venous eczema, lymphedema 1
• Reduce underlying edema through elevation and compression stockings 1
• Consider prophylactic antibiotics for patients with 3-4 episodes per year 1

Common Pitfalls

1. Misdiagnosis: Venous stasis dermatitis, contact dermatitis, eczema, and lymphedema can mimic cellulitis 4
2. Inadequate coverage: Ensure appropriate coverage for the likely pathogens based on clinical presentation 5
3. Insufficient duration: Ensure adequate treatment duration, especially for streptococcal infections 3
4. Failure to address underlying factors: Treating predisposing factors is crucial to prevent recurrence 1, 5
5. Not considering MRSA: Consider MRSA coverage in high-risk populations (athletes, children, prisoners, IV drug users) 5

Remember that cellulitis is primarily a clinical diagnosis, and microbiological diagnosis is often unobtainable due to poor sensitivity of culture specimens 4. Treatment failure should prompt consideration of resistant organisms or conditions that mimic cellulitis 5.