What are the treatment options for skin infections caused by MRSA?

Treatment Options for MRSA Skin Infections

For MRSA skin infections, first-line treatment includes incision and drainage for abscesses, followed by appropriate antibiotic therapy with oral options like trimethoprim-sulfamethoxazole, doxycycline, clindamycin, or linezolid based on infection severity and patient factors. 1

Classification and Initial Management

Purulent Skin Infections (abscesses, furuncles, carbuncles)

1. Primary treatment: Incision and drainage (I&D) (A-II) 1
2. When to add antibiotics (after I&D):
   • Severe or extensive disease/rapid progression with cellulitis
   • Signs of systemic illness
   • Immunosuppression or comorbidities (diabetes, HIV)
   • Extremes of age
   • Difficult-to-drain locations (face, hand, genitalia)
   • Associated septic phlebitis
   • Lack of response to I&D alone 1

Purulent Cellulitis (with exudate but no drainable abscess)

• Empiric MRSA coverage is recommended pending cultures (A-II)
• Duration: 5-10 days, based on clinical response 1

Non-purulent Cellulitis

• Primary coverage for β-hemolytic streptococci with β-lactams
• Add MRSA coverage if:
  • No response to β-lactam therapy
  • Signs of systemic toxicity 1

Antibiotic Options for MRSA Skin Infections

Outpatient Treatment (Oral Options)

1. Trimethoprim-sulfamethoxazole (TMP-SMX) (A-II)

   • Dosage: 1-2 DS tablets PO twice daily
   • Caution: Not recommended in 3rd trimester pregnancy or children <2 months
   • Note: Limited activity against β-hemolytic streptococci

2. Doxycycline/Minocycline (A-II)

   • Dosage: Doxycycline 100 mg PO twice daily
   • Contraindicated in children <8 years and pregnancy
   • Note: Limited activity against β-hemolytic streptococci

3. Clindamycin (A-II)

   • Dosage: 300-450 mg PO three times daily
   • Advantage: Covers both MRSA and β-hemolytic streptococci
   • Caution: Higher risk of C. difficile infection
   • Check local resistance rates (should be <10%)

4. Linezolid (A-II)

   • Dosage: 600 mg PO twice daily
   • Advantage: Excellent bioavailability, covers both MRSA and streptococci
   • Disadvantage: Higher cost, risk of myelosuppression with prolonged use
   • Clinical trials show superior outcomes compared to vancomycin 2

5. Tedizolid (A-I)

   • Dosage: 200 mg PO once daily for 6 days
   • FDA-approved for ABSSSI including MRSA 3
   • Advantage: Once-daily dosing

Inpatient Treatment (Complicated SSTI)

1. Vancomycin IV (A-I)

   • Dosage: 15-20 mg/kg IV every 8-12 hours
   • Gold standard for parenteral MRSA therapy

2. Linezolid (A-I)

   • Dosage: 600 mg IV/PO twice daily
   • Advantage: IV-to-oral switch with identical bioavailability

3. Daptomycin (A-I)

   • Dosage: 4 mg/kg IV once daily
   • Higher doses (6-10 mg/kg) for bacteremia

4. Telavancin (A-I)

   • Dosage: 10 mg/kg IV once daily

5. Ceftaroline (A-I)

   • Newer cephalosporin with MRSA activity

Special Considerations

Combination Therapy

• If coverage for both MRSA and β-hemolytic streptococci is needed:
  • Use clindamycin alone (A-II)
  • TMP-SMX or tetracycline plus β-lactam (e.g., amoxicillin) (A-II)
  • Linezolid alone (A-II) 1

Important Cautions

• Rifampin: Should not be used as monotherapy due to rapid resistance development; not recommended as adjunctive therapy for SSTI (A-III) 1
• Cultures: Obtain cultures from abscesses and purulent infections when:
  • Antibiotic therapy is being used
  • Severe local infection or systemic illness is present
  • Patient has not responded to initial treatment
  • Concern for outbreak exists 1

Treatment Algorithm

1. Assess infection type: Purulent vs. non-purulent
2. For abscesses: Perform I&D; add antibiotics only if criteria met
3. For purulent cellulitis: Start MRSA coverage empirically
4. For non-purulent cellulitis: Start β-lactam; add MRSA coverage if poor response
5. Select antibiotic based on:
   • Severity (outpatient vs. inpatient)
   • Need for streptococcal coverage
   • Patient factors (allergies, pregnancy, age)
   • Local resistance patterns

Monitoring and Follow-up

• Reassess in 48-72 hours for clinical improvement
• Consider treatment failure if no improvement after 3 days
• Complete 5-10 days for outpatient treatment and 7-14 days for inpatient treatment
• Longer durations may be needed for immunocompromised patients or extensive disease

The 2018 WSES/SIS-E consensus conference confirms these recommendations, emphasizing that 7-14 days of therapy is appropriate for most MRSA skin infections, with treatment duration individualized based on clinical response 1.