What antibiotics are used to treat cellulitis?

Antibiotic Treatment for Cellulitis

For typical uncomplicated cellulitis, a 5-day course of an antibiotic active against streptococci is the recommended first-line treatment, with options including penicillin, amoxicillin, dicloxacillin, cephalexin, or clindamycin. 1

Classification and Antibiotic Selection

Non-purulent Cellulitis (No drainage, exudate, or abscess)

• First-line therapy: β-lactam antibiotics targeting streptococci 1

  • Penicillin
  • Amoxicillin
  • Dicloxacillin
  • Cephalexin (500 mg four times daily)
  • Amoxicillin-clavulanate

• Duration: 5 days is sufficient if clinical improvement occurs; extend if no improvement 1

• For penicillin-allergic patients: Clindamycin (300-450 mg three times daily) 1

Purulent Cellulitis (With drainage or exudate)

• First-line therapy: Empiric coverage for CA-MRSA pending culture results 1

  • Clindamycin (strong evidence) 1
  • Trimethoprim-sulfamethoxazole (TMP-SMX) 1
  • Doxycycline or minocycline 1
  • Linezolid (for severe cases) 1

• Duration: 5-10 days, individualized based on clinical response 1

When Both Streptococcal and MRSA Coverage is Needed

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

Hospitalized Patients with Complicated SSTI

• Intravenous options:

  • Vancomycin 1, 2
  • Linezolid 600 mg twice daily 1
  • Daptomycin 4 mg/kg once daily 1
  • Telavancin 10 mg/kg once daily 1
  • Clindamycin 600 mg three times daily 1

• Duration: 7-14 days based on clinical response 1

Special Considerations

When to Consider MRSA Coverage

• Penetrating trauma, especially from illicit drug use 1
• Purulent drainage 1
• Evidence of MRSA infection elsewhere 1
• Nasal colonization with MRSA 1
• Injection drug use 1
• Systemic inflammatory response syndrome (SIRS) 1
• Athletes, children, men who have sex with men, prisoners, military recruits, residents of long-term care facilities 3

When to Obtain Cultures

• Patients with malignancy on chemotherapy 1
• Neutropenia 1
• Severe cell-mediated immunodeficiency 1
• Immersion injuries 1
• Animal bites 1
• Severe systemic features (high fever, hypotension) 1
• Patients treated with antibiotics who are not responding 1

Adjunctive Measures

• Elevation of the affected area to promote drainage of edema 1
• Treatment of predisposing conditions (tinea pedis, venous eczema, trauma) 1
• Systemic corticosteroids (prednisone 40 mg daily for 7 days) may be considered in non-diabetic adults 1

Common Pitfalls to Avoid

1. Overuse of broad-spectrum antibiotics: Studies show narrow-spectrum antibiotics targeting streptococci are effective for typical cellulitis 4

2. Unnecessary MRSA coverage: MRSA is an unusual cause of typical non-purulent cellulitis; a study showed β-lactam therapy was successful in 96% of cellulitis cases 1

3. Prolonged treatment courses: 5 days is as effective as 10 days for uncomplicated cellulitis if clinical improvement occurs 1

4. Failure to address predisposing factors: Examine interdigital toe spaces for fissuring or maceration that may harbor pathogens 1

5. Misdiagnosis: Many clinical conditions can mimic cellulitis; consider alternative diagnoses if no improvement with appropriate therapy 3

By following these evidence-based guidelines for antibiotic selection based on the type of cellulitis and patient risk factors, clinicians can effectively treat cellulitis while practicing appropriate antibiotic stewardship.