What antibiotic regimen is recommended for the treatment of Methicillin-resistant Staphylococcus aureus (MRSA) cellulitis?

Treatment of MRSA Cellulitis

For MRSA cellulitis, the recommended first-line oral antibiotics include clindamycin, trimethoprim-sulfamethoxazole (TMP-SMX), tetracyclines (doxycycline or minocycline), or linezolid, with treatment duration of 5-10 days based on clinical response. 1

Classification and Initial Approach

• Cellulitis should first be classified as either purulent or nonpurulent to guide appropriate therapy 1:

  • Purulent cellulitis: Associated with purulent drainage or exudate without a drainable abscess
  • Nonpurulent cellulitis: No purulent drainage, exudate, or associated abscess

• For purulent cellulitis, empirical therapy for CA-MRSA is recommended pending culture results 1

• For nonpurulent cellulitis, empirical therapy for β-hemolytic streptococci is recommended initially, with MRSA coverage added if there is no response to β-lactam therapy or if systemic toxicity is present 1

Outpatient Treatment Options for MRSA Cellulitis

First-line oral options:

• Clindamycin: 300-450 mg orally three times daily for adults; 10-13 mg/kg/dose orally every 6-8 hours (not exceeding 40 mg/kg/day) for children 1

  • Advantage: Provides coverage for both MRSA and β-hemolytic streptococci
  • Caution: Monitor for C. difficile-associated disease

• TMP-SMX: 1-2 double-strength tablets orally twice daily 1

  • Advantage: High success rates in MRSA-prevalent settings 2
  • Limitation: Limited activity against β-hemolytic streptococci
  • Contraindication: Not recommended for pregnant women in third trimester or children <2 months 1

• Tetracyclines: Doxycycline 100 mg orally twice daily or minocycline 200 mg initially, then 100 mg orally twice daily 1

  • Contraindication: Should not be used in children <8 years of age 1

• Linezolid: 600 mg orally twice daily for adults; 10 mg/kg/dose orally every 8 hours (not exceeding 600 mg/dose) for children <12 years 1, 3

  • Advantage: High efficacy against MRSA with 91% cure rates in clinical trials 3
  • Limitation: More expensive than other options 1

Combination therapy options:

• If coverage for both β-hemolytic streptococci and MRSA is desired, options include:
  • TMP-SMX or a tetracycline in combination with a β-lactam (e.g., amoxicillin) 1
  • This approach addresses the limited streptococcal coverage of TMP-SMX and tetracyclines

Inpatient Treatment for Complicated MRSA Cellulitis

• For hospitalized patients with complicated SSTI (deeper infections, surgical/traumatic wound infections, major abscesses, or infected ulcers/burns), options include 1:

  • Vancomycin: 15-20 mg/kg/dose IV every 8-12 hours (A-I) 1
  • Linezolid: 600 mg IV/PO twice daily (A-I) 1, 3
  • Daptomycin: 4 mg/kg/dose IV once daily (A-I) 1, 4
  • Telavancin: 10 mg/kg/dose IV once daily (A-I) 1
  • Clindamycin: 600 mg IV/PO three times daily (A-III) 1

• Treatment duration for complicated infections: 7-14 days, individualized based on clinical response 1

Pediatric Considerations

• For children with MRSA cellulitis 1:

  • Vancomycin is recommended for hospitalized children (A-II)
  • Clindamycin (10-13 mg/kg/dose IV every 6-8 hours) is an option if local resistance rates are low (<10%)
  • Linezolid is an alternative: 600 mg PO/IV twice daily for children >12 years; 10 mg/kg/dose every 8 hours for children <12 years

• Tetracyclines should not be used in children <8 years of age 1

Important Clinical Pearls

• Obtain cultures from purulent drainage before starting antibiotics to confirm MRSA and guide therapy 1, 5

• Rifampin should not be used as monotherapy or adjunctive therapy for treatment of MRSA skin infections due to rapid development of resistance 1

• For patients with systemic toxicity and/or rapidly progressive infection despite oral antibiotics, inpatient management is recommended 1, 5

• The optimal duration of therapy is 5-10 days for uncomplicated infections, but should be extended based on clinical response for more severe cases 1

• Prevention of recurrence includes keeping wounds covered with clean, dry bandages and maintaining good personal hygiene 1, 5