What is the recommended treatment for cellulitis?

Treatment of Cellulitis

For cellulitis, the recommended first-line treatment is cephalexin 500mg 3-4 times daily for 5-6 days or clindamycin 300-450mg three times daily for 5-6 days for mild non-purulent infections. 1

Classification and Treatment Approach

Treatment should be based on:

• Classification of infection (purulent vs. non-purulent)
• Clinical severity
• Suspected pathogen

Non-purulent Cellulitis (Most Common)

1. First-line options (5-6 days treatment):

   • Cephalexin 500mg 3-4 times daily
   • Clindamycin 300-450mg three times daily
   • Amoxicillin-clavulanate 875/125mg twice daily

2. For suspected streptococcal infections:

   • Penicillin is the first-line treatment 1

3. For suspected MSSA infections:

   • Dicloxacillin or cephalexin 1

Purulent Cellulitis

1. Primary treatment:

   • Incision and drainage for collections 1

2. Mild cases with systemic symptoms:

   • TMP-SMX, doxycycline, or clindamycin 1

3. Severe cases:

   • Vancomycin IV, linezolid, daptomycin, or ceftaroline 1, 2

MRSA Considerations

• MRSA coverage is not routinely recommended for non-purulent cellulitis 3

• Consider MRSA coverage for specific risk groups:

  • Athletes
  • Children
  • Men who have sex with men
  • Prisoners
  • Military recruits
  • Long-term care facility residents
  • Prior MRSA exposure
  • IV drug users 4

• MRSA treatment options:

  • Mild cases: TMP-SMX, doxycycline, or clindamycin
  • Severe cases: Vancomycin 15-20 mg/kg IV every 8-12 hours
  • Alternative for vancomycin-resistant/intolerant patients: Daptomycin 6 mg/kg IV every 24 hours 1

Duration of Treatment

• Standard duration: 5-6 days for most skin infections 1
• Extended duration: 10-21 days for severe infections 1
• Clinical improvement should be seen within 72 hours; if not, reevaluate treatment plan 1

Special Considerations

• Immunocompromised patients: May require extended treatment based on clinical response 1
• Necrotizing fasciitis: Requires aggressive treatment with clindamycin plus piperacillin-tazobactam or ceftriaxone plus metronidazole, with or without vancomycin 1

Prevention of Recurrence

• Address predisposing factors:
  • Treat tinea pedis and other toe web abnormalities
  • Manage edema, obesity, and venous insufficiency
  • Consider prophylactic antibiotics for frequent episodes 1

Important Caveats

1. Diagnostic challenges: Cellulitis lacks a gold standard for diagnosis and can be confused with pseudocellulitis conditions like venous stasis dermatitis, contact dermatitis, and lymphedema 3

2. Culture limitations: The majority of cellulitis cases are nonculturable, making the causative bacteria unknown in approximately 85% of cases 4

3. Treatment failures: If no improvement is seen within 72 hours, consider:

   • Resistant organisms
   • Secondary conditions mimicking cellulitis
   • Underlying complicating conditions (immunosuppression, liver disease, kidney disease) 4
   • Unusual pathogens (like Proteus mirabilis in patients with compromised tissue) 5

4. Combination therapy: Adding TMP-SMX to cephalexin has not shown improved outcomes for uncomplicated cellulitis 6, supporting guidelines that recommend against routine MRSA coverage for non-purulent cellulitis.