What antibiotics are recommended for the treatment of cellulitis?

Antibiotic Treatment for Cellulitis

For typical cases of cellulitis without systemic signs of infection, an antimicrobial agent active against streptococci should be used for 5 days, with extension if the infection has not improved within this time period. 1

Treatment Algorithm Based on Severity

Mild Cellulitis (without systemic signs)

• First-line therapy: Antibiotics active against streptococci 1

  • Penicillin
  • Amoxicillin
  • Dicloxacillin
  • Cephalexin (250-500 mg every 6 hours) 2
  • Clindamycin

• Duration: 5-6 days is sufficient if clinical improvement occurs 1

Moderate Cellulitis (with systemic signs)

• Recommended therapy: Coverage for both streptococci and MSSA 1
  • Cephalexin (500 mg every 6 hours)
  • Dicloxacillin
  • Clindamycin (covers both streptococci and S. aureus)

Severe Cellulitis (with SIRS, altered mental status, or hemodynamic instability)

• Recommended therapy: Coverage for both MRSA and streptococci 1

  • Vancomycin (15 mg/kg every 12 hours IV)
  • Linezolid (600 mg twice daily IV or PO) 3
  • Daptomycin (4 mg/kg/dose IV once daily)
  • Clindamycin (600 mg IV or PO 3 times daily)

• For severely compromised patients: Vancomycin plus either piperacillin-tazobactam or imipenem/meropenem 1

Special Considerations

When to Consider MRSA Coverage

MRSA coverage should be added when cellulitis is associated with:

• Penetrating trauma
• Evidence of MRSA infection elsewhere
• Nasal colonization with MRSA
• Injection drug use
• Systemic inflammatory response syndrome (SIRS) 1
• High local prevalence of community-associated MRSA 4

High MRSA Prevalence Areas

In areas with high MRSA prevalence, consider:

• Trimethoprim-sulfamethoxazole (higher success rates than cephalexin in some studies) 4
• Clindamycin
• Linezolid 1

Adjunctive Measures

• Elevation of the affected area to promote drainage of edema 1
• Treatment of predisposing factors such as edema, obesity, eczema, venous insufficiency, and toe web abnormalities 1
• Systemic corticosteroids (prednisone 40 mg daily for 7 days) may be considered in non-diabetic adults to hasten resolution 1

Duration of Therapy

The recommended duration is 5 days, with extension if the infection has not improved within this time period 1. Recent evidence supports shorter courses (5-6 days) being as effective as longer courses (10-14 days) for uncomplicated cellulitis 1.

Recurrent Cellulitis Management

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

• Prophylactic antibiotics: oral penicillin or erythromycin twice daily for 4-52 weeks
• Intramuscular benzathine penicillin every 2-4 weeks 1

Common Pitfalls

1. Failure to examine interdigital toe spaces in lower-extremity cellulitis - treating fissuring or maceration can reduce recurrence 1
2. Unnecessary MRSA coverage for typical cellulitis - MRSA is an unusual cause of typical cellulitis 1
3. Prolonged antibiotic courses - 5 days is sufficient for most cases 1
4. Failure to elevate the affected area - an important and often neglected aspect of treatment 1
5. Missing underlying conditions that may predispose to infection or recurrence 1

By following this evidence-based approach to antibiotic selection for cellulitis, clinicians can provide effective treatment while minimizing unnecessary broad-spectrum antibiotic use and optimizing patient outcomes.