What is the initial management and antibiotic therapy for purulent vs nonpurulent cellulitis?

Management of Purulent vs. Nonpurulent Cellulitis

Distinguishing Characteristics

The key distinction between purulent and nonpurulent cellulitis is the presence of purulent drainage or exudate and/or an associated abscess, which guides antibiotic therapy selection and management approach. 1

Purulent Cellulitis

• Defined as cellulitis associated with purulent drainage or exudate
• May be associated with a drainable abscess
• Primary causative organism: Staphylococcus aureus (including CA-MRSA)
• Requires empiric coverage for CA-MRSA pending culture results

Nonpurulent Cellulitis

• Defined as cellulitis with no purulent drainage or exudate and no associated abscess
• Primary causative organisms: β-hemolytic streptococci
• Empiric therapy should target β-hemolytic streptococci
• CA-MRSA coverage only needed if patient fails β-lactam therapy or has systemic toxicity

Initial Management

Purulent Cellulitis

1. Incision and drainage (I&D) is the primary treatment for any associated abscess 1

2. Obtain cultures from abscesses and purulent drainage before starting antibiotics 1

3. Antibiotic therapy (5-10 days):

   • Outpatient options (empiric coverage for CA-MRSA):
     • Clindamycin 300-450 mg PO three times daily (A-II)
     • Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 DS tablets twice daily (A-II)
     • Doxycycline or minocycline 100 mg PO twice daily (A-II)
     • Linezolid 600 mg PO twice daily (A-II)

4. Hospitalized patients with complicated SSTI (deeper infections, surgical/traumatic wound infection, major abscesses):

   • IV vancomycin (A-I)
   • Linezolid 600 mg PO/IV twice daily (A-I)
   • Daptomycin 4 mg/kg/dose IV once daily (A-I)
   • Telavancin 10 mg/kg/dose IV once daily (A-I)
   • Clindamycin 600 mg IV/PO three times daily (A-III)

Nonpurulent Cellulitis

1. Antibiotic therapy (5-10 days):

   • Outpatient options (empiric coverage for β-hemolytic streptococci):
     • Cephalexin 500 mg PO four times daily
     • Dicloxacillin 500 mg PO four times daily
     • Amoxicillin-clavulanate 875/125 mg PO twice daily
     • Clindamycin 300-450 mg PO three times daily (for penicillin-allergic patients)

2. Add CA-MRSA coverage only if:

   • No response to β-lactam therapy
   • Patient has systemic toxicity

3. Hospitalized patients with nonpurulent cellulitis:

   • β-lactam antibiotic (e.g., cefazolin) is appropriate
   • Modify to MRSA-active therapy if no clinical response (A-II)

Special Considerations

When to Consider Combined Coverage

If coverage for both β-hemolytic streptococci and CA-MRSA is desired:

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

Antibiotic Duration

• Standard duration: 5-10 days for uncomplicated cases
• Duration should be individualized based on clinical response
• Complicated infections may require 7-14 days of therapy 1

Diabetic Patients

• Require careful evaluation for deep tissue involvement
• Consider broader coverage including MRSA
• Evaluate for osteomyelitis, especially with diabetic foot infections 2

Treatment Failure and Follow-up

1. If no improvement after 5 days:

   • For nonpurulent cellulitis: Consider adding MRSA coverage
   • For purulent cellulitis: Reassess drainage adequacy, consider imaging
   • Consider imaging (preferably MRI) to assess for deeper complications 2

2. Monitor daily for clinical response:

   • Decreasing erythema, edema, and pain
   • Resolution of systemic symptoms (fever, tachycardia)

Prevention of Recurrence

• Identify and treat predisposing conditions (tinea pedis, eczema, trauma, edema)
• Maintain good personal hygiene
• Keep draining wounds covered with clean, dry bandages
• Consider prophylactic antibiotics for patients with 3-4 episodes per year 2

Note: Rifampin should not be used as a single agent or as adjunctive therapy for the treatment of SSTI (A-III) 1.