What is the treatment for cellulitis (bacterial skin infection)?

Treatment of Cellulitis

For typical cases of cellulitis, a 5-day course of oral antibiotics active against streptococci is the recommended first-line treatment, with options including penicillin, amoxicillin, amoxicillin-clavulanate, dicloxacillin, cephalexin, or clindamycin. 1, 2

First-Line Antibiotic Selection

• For non-purulent, uncomplicated cellulitis, oral antibiotics active against streptococci should be used, as streptococci are the predominant causative organisms 1, 2
• Recommended first-line options include:
  • Penicillin 1, 2
  • Amoxicillin 1, 2
  • Amoxicillin-clavulanate 1, 2
  • Dicloxacillin 1, 2
  • Cephalexin (500 mg four times daily) 1, 2
  • Clindamycin (150-300 mg every 6 hours for serious infections; 300-450 mg every 6 hours for more severe infections) 1, 3

Duration of Therapy

• A 5-day course of antimicrobial therapy is as effective as a 10-day course for uncomplicated cellulitis if clinical improvement has occurred by day 5 1, 2
• Treatment should be extended if the infection has not improved within the initial 5-day period 4, 2
• For β-hemolytic streptococcal infections, treatment should continue for at least 10 days 3

When to Consider MRSA Coverage

• MRSA is an unusual cause of typical cellulitis, and routine coverage is unnecessary 1

• Consider adding MRSA coverage only in specific situations:

  • Cellulitis associated with penetrating trauma, especially from illicit drug use 1, 2
  • Presence of purulent drainage 1, 2
  • Evidence of MRSA infection elsewhere 1, 2
  • History of previous MRSA infections 5

• Options for MRSA coverage include:

  • Intravenous options: vancomycin, daptomycin, linezolid, or telavancin 1, 6
  • Oral options: clindamycin alone, or combination of trimethoprim-sulfamethoxazole (TMP-SMX) or doxycycline with a β-lactam 1, 2

Adjunctive Measures

• Elevation of the affected area is important to promote gravity drainage of edema and inflammatory substances 1, 2
• Identify and treat predisposing conditions such as:
  • Tinea pedis 2
  • Trauma to the area 2
  • Venous eczema or venous insufficiency 1, 2
• Systemic corticosteroids (e.g., prednisone 40 mg daily for 7 days) could be considered in non-diabetic adult patients to reduce inflammation and hasten resolution 1, 2
• Anti-inflammatory therapy may help speed resolution of cellulitis-related inflammation 7

Hospitalization Criteria

• Consider hospitalization for patients with:
  • Severe infections with systemic inflammatory response syndrome 2
  • Altered mental status 2
  • Hemodynamic instability 2
  • Concern for deeper or necrotizing infection 2
  • Immunocompromise 2
  • Failure of outpatient treatment 2

Prevention of Recurrence

• For patients with frequent episodes of cellulitis (annual recurrence rates of about 8%-20%), consider prophylactic antibiotics 1, 2
• Options include oral penicillin, erythromycin, or intramuscular benzathine penicillin 4, 2
• Address underlying conditions that predispose to recurrence, such as treating tinea pedis and managing venous insufficiency and lymphedema 2, 8

Common Pitfalls to Avoid

• Don't automatically add MRSA coverage for typical non-purulent cellulitis without specific risk factors 1, 2
• Don't extend treatment unnecessarily beyond 5 days if clinical improvement has occurred 1, 2
• Don't forget to examine interdigital toe spaces in lower-extremity cellulitis, as treating fissuring or maceration may reduce recurrence 2, 8
• Don't overlook the importance of elevating the affected area, especially in patients with venous insufficiency or lymphedema 1, 2
• Don't rely on combination therapy with TMP-SMX plus cephalexin for pure cellulitis, as it has not been shown to be more efficacious than cephalexin alone 1, 9