What is the recommended treatment for Methicillin-resistant Staphylococcus aureus (MRSA) infections?

Treatment of MRSA Infections

For skin and soft tissue MRSA infections, incision and drainage is the primary treatment, with oral antibiotics (trimethoprim-sulfamethoxazole, doxycycline, or clindamycin) added for severe disease, systemic symptoms, or extensive involvement. 1

Initial Management

• Surgical drainage is the cornerstone of therapy - incision and drainage of abscesses must be performed whenever feasible, as failure to drain collections leads to treatment failure regardless of antibiotic choice 1, 2, 3
• Obtain cultures from purulent drainage before starting antibiotics to confirm MRSA and guide definitive therapy 4, 2, 3
• For simple abscesses or boils in otherwise healthy patients, incision and drainage alone may be adequate without antibiotics 1, 2, 3

When to Add Antibiotics to Drainage

Add antibiotics when any of the following are present 1:

• Severe or extensive disease involving multiple sites
• Rapid progression with surrounding cellulitis
• Signs of systemic illness (fever, tachycardia, hypotension)
• Immunosuppression or significant comorbidities (diabetes, renal failure)
• Extremes of age (very young or elderly)
• Difficult-to-drain locations (face, hands, genitalia)
• Lack of response to drainage alone after 48-72 hours

Outpatient Oral Antibiotic Options

For non-severe MRSA skin infections:

• Trimethoprim-sulfamethoxazole (TMP-SMX): 1-2 double-strength tablets orally twice daily - first-line choice 1, 4, 3
• Doxycycline: 100 mg orally twice daily - equally effective alternative 1, 2, 3
• Clindamycin: 300-450 mg orally three times daily - use only if local resistance rates <10% 1, 3
• Linezolid: 600 mg orally twice daily - highly effective but expensive, reserve for failures of other agents 1, 3

Important caveat: TMP-SMX and tetracyclines do not adequately cover beta-hemolytic streptococci 1, 3. If streptococcal coverage is also needed (nonpurulent cellulitis), either use clindamycin alone or combine TMP-SMX/doxycycline with amoxicillin 1.

Inpatient IV Antibiotic Options

For complicated skin infections, bacteremia, or systemic toxicity requiring hospitalization:

• Vancomycin: 15-20 mg/kg IV every 8-12 hours - traditional first-line for serious MRSA infections 1, 3
• Daptomycin: 4 mg/kg IV once daily for skin infections; 6 mg/kg IV once daily for bacteremia - FDA-approved alternative with proven efficacy 1, 5
• Linezolid: 600 mg IV twice daily - excellent tissue penetration, can transition seamlessly to oral 1, 6
• Telavancin: 10 mg/kg IV once daily - alternative for complicated skin infections 1
• Ceftaroline: 600 mg IV every 12 hours - newer anti-MRSA cephalosporin option 7

Treatment Duration

• Uncomplicated skin infections: 5-10 days 1, 4, 2, 3
• Complicated skin infections: 7-14 days 1, 2, 3
• Uncomplicated bacteremia (no endocarditis, no prosthetics, blood cultures clear within 2-4 days, defervescence within 72 hours, no metastatic foci): minimum 2 weeks 1
• Complicated bacteremia: 4-6 weeks depending on extent of infection 1
• Infective endocarditis: 6 weeks 1

Special Considerations for Bacteremia

• Remove all infected intravascular devices and prosthetic materials - failure to do so increases mortality and relapse rates 1
• Obtain repeat blood cultures 2-4 days after initial positive cultures to document clearance 1, 2
• Perform echocardiography on all adults with MRSA bacteremia - transesophageal echo (TEE) is preferred over transthoracic (TTE) for detecting vegetations and complications 1
• Do NOT add gentamicin or rifampin to vancomycin for bacteremia or native valve endocarditis - combination therapy does not improve outcomes and increases toxicity 1
• For endocarditis, some experts recommend higher daptomycin doses of 8-10 mg/kg IV once daily, though this is based on limited evidence 1

Pediatric Dosing

• Clindamycin: 10-13 mg/kg/dose orally every 6-8 hours (maximum 40 mg/kg/day) 4, 3
• TMP-SMX: 4-6 mg/kg/dose (trimethoprim component) orally every 12 hours 3
• Vancomycin IV: 10-15 mg/kg/dose every 6-24 hours depending on age and renal function 6
• Avoid tetracyclines in children under 8 years of age due to tooth discoloration 4, 3

Prevention of Recurrence

• Keep draining wounds covered with clean, dry bandages 4, 2, 3
• Maintain rigorous hand hygiene with soap and water or alcohol-based gel 2, 3
• Avoid sharing personal items (towels, razors, clothing) 2
• Consider decolonization with intranasal mupirocin and chlorhexidine body washes for recurrent infections despite optimal wound care 2, 3

Critical Pitfalls to Avoid

• Never use beta-lactam antibiotics alone (cephalexin, dicloxacillin) for suspected MRSA - they have no activity against methicillin-resistant strains 2
• Do not use rifampin as monotherapy or adjunctive therapy for skin infections - it does not improve outcomes and promotes resistance 1, 2
• Daptomycin cannot be used for pneumonia - it is inactivated by pulmonary surfactant 7, 8
• Reassess clinically within 48-72 hours to ensure appropriate response - persistent fever or worsening symptoms require imaging to identify undrained collections or metastatic foci 1, 3