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 antibiotics active against streptococci is recommended as first-line therapy. 1

Classification and Treatment Algorithm

Mild Cellulitis (without systemic signs)

• First-line treatment:

  • Penicillin (250-500 mg every 6 hours orally) 1
  • Amoxicillin (500 mg three times daily orally)
  • Cephalexin (500 mg every 6 hours orally) 1
  • Dicloxacillin (250 mg every 6 hours orally) 2
  • Clindamycin (300-450 mg three times daily orally) - for penicillin-allergic patients

• Duration: 5 days, extending only if infection has not improved within this period 1, 3

Moderate Cellulitis (with systemic signs)

• Treatment options:
  • Coverage for both streptococci and MSSA
  • Dicloxacillin (500 mg every 6 hours orally) 2
  • Cefazolin (1 g every 8 hours IV) for hospitalized patients 1
  • Clindamycin (600-900 mg IV every 8 hours) for penicillin-allergic patients

Severe Cellulitis (with SIRS or high-risk factors for MRSA)

• Treatment options:
  • Vancomycin (15 mg/kg every 12 hours IV) 1
  • Linezolid (600 mg every 12 hours orally or IV)
  • Daptomycin (4 mg/kg daily IV)
  • For severely compromised patients: Vancomycin plus either piperacillin-tazobactam or imipenem/meropenem 1

Special Considerations

When to suspect MRSA

Coverage for MRSA should be considered in patients with:

• Penetrating trauma
• Evidence of MRSA infection elsewhere
• Nasal colonization with MRSA
• Injection drug use
• Systemic inflammatory response syndrome (SIRS)
• Purulent drainage 1

When to hospitalize

Hospitalization is recommended for patients with:

• Signs of deeper or necrotizing infection
• Poor adherence to therapy
• Severe immunocompromise
• Failure of outpatient treatment
• SIRS, altered mental status, or hemodynamic instability 1

Adjunctive Measures

• Elevate the affected area to reduce edema 1
• Examine and treat interdigital toe spaces in lower extremity cellulitis to prevent recurrence 1
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults 1
• Identify and treat predisposing conditions (edema, obesity, eczema, venous insufficiency) 1

Management of Recurrent Cellulitis

• Identify and treat local causes (pilonidal cyst, hidradenitis suppurativa, foreign material) 1
• Consider prophylactic antibiotics for patients with 3-4 episodes per year:
  • Oral penicillin or erythromycin twice daily for 4-52 weeks
  • Intramuscular benzathine penicillin every 2-4 weeks 1
• Consider decolonization regimen for recurrent S. aureus infections:
  • Intranasal mupirocin twice daily for 5 days
  • Daily chlorhexidine washes
  • Daily decontamination of personal items 1

Common Pitfalls and Caveats

• Cultures of blood or cutaneous aspirates are not routinely recommended except in immunocompromised patients, those with malignancy on chemotherapy, neutropenia, immersion injuries, or animal bites 1
• MRSA is an unusual cause of typical cellulitis, and empiric coverage is usually unnecessary unless specific risk factors are present 1
• Cellulitis can be difficult to diagnose due to mimickers such as venous stasis dermatitis, contact dermatitis, and lymphedema 4
• Symptoms may worsen initially after starting antibiotics due to pathogen destruction releasing inflammatory mediators 1
• If no improvement after 5 days of appropriate therapy, consider resistant organisms or alternative diagnoses 1, 5

The evidence strongly supports a 5-day course of antibiotics for uncomplicated cellulitis, with extension only if improvement is not seen within this timeframe. This approach balances effective treatment with antimicrobial stewardship principles 1, 3.