What is the recommended treatment for cellulitis?

Treatment of Cellulitis

For typical cases of cellulitis without systemic signs of infection, a 5-day course of an antimicrobial agent active against streptococci is the recommended treatment. 1

Classification and Initial Assessment

Treatment approach depends on the classification of cellulitis:

1. Nonpurulent cellulitis (no drainage/exudate, no abscess)

   • Primary pathogen: β-hemolytic streptococci
   • First-line therapy: β-lactam antibiotics

2. Purulent cellulitis (with drainage/exudate)

   • Consider MRSA coverage empirically
   • Obtain cultures when possible

3. Severity assessment:

   • Mild: Outpatient treatment, no systemic signs
   • Moderate: Systemic signs present
   • Severe: Requires hospitalization (SIRS, altered mental status, hemodynamic instability)

Antibiotic Selection

Outpatient Treatment

For Nonpurulent Cellulitis (most common):

• First-line options (targeting streptococci):
  • Penicillin
  • Amoxicillin
  • Dicloxacillin
  • Cephalexin (500 mg four times daily)
  • Clindamycin (if penicillin-allergic)

For Purulent Cellulitis or MRSA Risk Factors:

• MRSA coverage indicated if:

  • Penetrating trauma history
  • Evidence of MRSA infection elsewhere
  • MRSA nasal colonization
  • Injection drug use
  • Systemic inflammatory response syndrome
  • Failure to respond to β-lactam therapy 1

• MRSA treatment options:

  • Clindamycin (if local resistance <10-15%)
  • Trimethoprim-sulfamethoxazole (TMP-SMX)
  • Doxycycline or minocycline
  • Linezolid 1

• For dual coverage (streptococci + MRSA):

  • Clindamycin alone
  • TMP-SMX or tetracycline plus β-lactam (e.g., amoxicillin)
  • Linezolid alone 1

Inpatient Treatment (Complicated SSTI)

• IV options:
  • Vancomycin
  • Linezolid 600 mg twice daily
  • Daptomycin 4 mg/kg/day
  • Telavancin 10 mg/kg/day
  • Clindamycin 600 mg three times daily 1

Duration of Therapy

• 5 days of antibiotic therapy is sufficient for uncomplicated cellulitis 1, 2
• Extend treatment only if infection has not improved within this period
• A randomized controlled trial showed 5 days of levofloxacin was equivalent to 10 days for uncomplicated cellulitis (98% success rate in both groups) 2

Adjunctive Measures

1. Elevation of the affected area to promote gravity drainage of edema 1

2. Treat predisposing factors:

   • Tinea pedis (especially in lower extremity cellulitis)
   • Interdigital toe space maceration
   • Venous insufficiency
   • Lymphedema
   • Obesity 1

3. Consider systemic corticosteroids in nondiabetic adults (prednisone 40 mg daily for 7 days) to reduce inflammation and hasten resolution 1

Management of Recurrent Cellulitis

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

• Consider prophylactic antibiotics:
  • Oral penicillin or erythromycin twice daily for 4-52 weeks
  • Intramuscular benzathine penicillin every 2-4 weeks 1

Common Pitfalls to Avoid

1. Unnecessary MRSA coverage for typical nonpurulent cellulitis - studies show β-lactams alone are effective in most cases 3

2. Prolonged antibiotic courses - 5 days is as effective as longer courses for uncomplicated cellulitis 1, 2

3. Failure to examine interdigital spaces in lower extremity cellulitis - treating underlying tinea pedis or maceration can prevent recurrence 1

4. Missing deeper infections - consider necrotizing fasciitis if there is:

   • Severe pain out of proportion to exam findings
   • Rapid progression
   • Skin necrosis or bullae
   • Crepitus or gas in tissues
   • Systemic toxicity 1

5. Unnecessary cultures in typical cases - cultures of blood or skin are not routinely recommended for uncomplicated cellulitis 1