What is the recommended workup and treatment for cellulitis?

Workup and Treatment for Cellulitis

For typical cases of cellulitis, diagnosis is clinical and cultures are unnecessary, with treatment focusing on antibiotics active against streptococci, typically a 5-day course of beta-lactam antibiotics. 1

Diagnosis

Clinical Features

• Rapidly spreading areas of erythema, swelling, tenderness, and warmth
• Sometimes accompanied by lymphangitis and regional lymph node inflammation
• Skin may have "orange peel" appearance (peau d'orange) due to cutaneous edema
• Possible development of vesicles, bullae, or cutaneous hemorrhage (petechiae/ecchymoses)
• Systemic manifestations usually mild but may include fever, tachycardia, confusion, hypotension, and leukocytosis 1

Diagnostic Workup

• Diagnosis primarily based on history and physical examination 2
• Cultures (blood, tissue aspirates, skin biopsies) are unnecessary for typical cases 1
• Blood cultures should be obtained only for:
  • Patients with malignancy
  • Severe systemic features (high fever, hypotension)
  • Unusual predisposing factors (immersion injury, animal bites, neutropenia, severe immunodeficiency) 1

Differential Diagnosis

• Important to differentiate from non-infectious conditions that mimic cellulitis:
  • Venous insufficiency
  • Eczema
  • Deep vein thrombosis
  • Gout 3
  • Inflammatory breast cancer 1

Treatment Algorithm

1. Mild Uncomplicated Cellulitis (outpatient)

• First-line therapy: Oral antibiotics active against streptococci 1
  • Penicillin
  • Amoxicillin
  • Amoxicillin-clavulanate
  • Dicloxacillin
  • Cephalexin
  • Clindamycin (for penicillin-allergic patients)
• Duration: 5 days (if clinical improvement occurs) 1
• Adjunctive measures:
  • Elevation of affected area 1
  • Treatment of predisposing conditions (tinea pedis, trauma, venous eczema) 1

2. Moderate to Severe Cellulitis (consider hospitalization)

• Indications for hospitalization:
  • SIRS (Systemic Inflammatory Response Syndrome)
  • Altered mental status
  • Hemodynamic instability
  • Concern for deeper/necrotizing infection
  • Poor adherence to therapy
  • Severely immunocompromised patient
  • Failure of outpatient treatment 1
• Treatment: Parenteral antibiotics
  • Nafcillin or oxacillin
  • Cefazolin
  • Clindamycin or vancomycin (for penicillin-allergic patients) 1

3. Special Considerations for MRSA

• MRSA is an unusual cause of typical cellulitis 1
• Consider MRSA coverage only if:
  • Associated with penetrating trauma (especially from illicit drug use)
  • Purulent drainage present
  • Concurrent evidence of MRSA infection elsewhere
  • Patient belongs to high-risk group (athletes, children, prisoners, military recruits, residents of long-term care facilities, prior MRSA exposure, IV drug users) 1, 2
• Treatment options for MRSA:
  • Intravenous: vancomycin, daptomycin, linezolid, or telavancin
  • Oral: doxycycline, clindamycin, or trimethoprim-sulfamethoxazole (SMX-TMP) 1

Prevention of Recurrence

• Identify and treat predisposing conditions:
  • Edema/lymphedema
  • Obesity
  • Eczema
  • Venous insufficiency
  • Toe web abnormalities 1
• Examine interdigital toe spaces and treat fissuring, scaling, or maceration 1
• For patients with 3-4 episodes 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. Misdiagnosis: Cellulitis is frequently misdiagnosed, leading to unnecessary hospitalizations and antibiotic overuse 4

2. Failure to improve: Consider:

   • Resistant organisms
   • Secondary conditions mimicking cellulitis
   • Underlying complicating conditions (immunosuppression, chronic liver/kidney disease) 2

3. Worsening after treatment initiation: May occur due to sudden destruction of pathogens releasing inflammatory enzymes

   • Systemic corticosteroids (prednisone 40 mg daily for 7 days) could be considered in non-diabetic adults 1

4. Inadequate treatment of predisposing factors: Each attack of cellulitis causes lymphatic inflammation and possibly permanent damage, leading to increased risk of recurrence 1

5. Unnecessary MRSA coverage: Beta-lactam monotherapy is recommended for typical cellulitis without abscess, ulcer, or purulent drainage 1

By following this evidence-based approach to diagnosis and management, clinicians can effectively treat cellulitis while minimizing complications and recurrence.