What is the recommended outpatient management for cellulitis?

Outpatient Management of Cellulitis

For typical cases of cellulitis without systemic signs of infection, a 5-day course of antibiotics active against streptococci is recommended as the primary outpatient management strategy. 1

Diagnostic Approach

• Cultures of blood or cutaneous aspirates are not routinely recommended for typical cases of cellulitis 1
• Blood cultures should be considered in patients with:
  • Malignancy on chemotherapy
  • Neutropenia
  • Severe cell-mediated immunodeficiency
  • Immersion injuries
  • Animal bites
  • Systemic inflammatory response syndrome (SIRS) 1

Antimicrobial Therapy Selection

First-line Treatment (Typical Cellulitis)

• Antibiotic choice: Select an agent active against streptococci 1
  • Penicillin
  • Amoxicillin
  • Dicloxacillin
  • Cephalexin (500 mg orally four times daily) 2
  • Clindamycin (for penicillin-allergic patients)

When to Cover for MRSA

Expand coverage to include MRSA 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

MRSA coverage options:

• Trimethoprim-sulfamethoxazole (TMP-SMX)
• Doxycycline or minocycline
• Clindamycin
• Linezolid 1

Combination Therapy Considerations

If coverage for both streptococci and MRSA is desired:

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

Duration of Therapy

• 5 days of antimicrobial therapy is recommended for uncomplicated cellulitis 1
• Treatment should be extended if the infection has not improved within this time period 1
• Recent evidence supports that 5-6 day courses are as effective as 10-day courses for uncomplicated cellulitis 1, 3

Adjunctive Measures

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

2. Treatment of predisposing factors 1:

   • Edema
   • Obesity
   • Eczema
   • Venous insufficiency
   • Toe web abnormalities

3. For lower-extremity cellulitis: Carefully examine interdigital toe spaces and treat any fissuring, scaling, or maceration to eradicate pathogen colonization 1

4. Consider systemic corticosteroids: Prednisone 40 mg daily for 7 days may be considered in non-diabetic adults with cellulitis 1

Criteria for Hospitalization

Hospitalization is recommended if:

• Patient has SIRS, altered mental status, or hemodynamic instability
• There is concern for deeper or necrotizing infection
• Patient has poor adherence to therapy
• Patient is severely immunocompromised
• Outpatient treatment is failing 1

Management of Recurrent Cellulitis

For patients with 3-4 episodes of cellulitis 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 and Caveats

1. MRSA consideration: While MRSA is an unusual cause of typical cellulitis, coverage should be considered in high-risk situations 1

2. Dosing considerations: Some evidence suggests that higher doses of antibiotics may be beneficial. A recent pilot study showed that high-dose cephalexin (1000 mg four times daily) had fewer treatment failures than standard-dose (500 mg four times daily), though with more minor adverse effects 4

3. Treatment failure: If no improvement occurs within 2-3 days, consider:

   • Resistant organisms
   • Secondary conditions mimicking cellulitis
   • Underlying complicating conditions (immunosuppression, chronic liver or kidney disease) 5

4. Purulent vs. nonpurulent cellulitis: For purulent cellulitis (with drainage or exudate), empirical therapy for CA-MRSA is recommended pending culture results 1

By following this structured approach to outpatient cellulitis management, clinicians can effectively treat most cases while minimizing unnecessary hospitalizations and antibiotic overuse.