What is the recommended treatment for a wound infection with Methicillin-resistant Staphylococcus aureus (MRSA)?

Treatment of MRSA Wound Infections

For MRSA wound infections, incision and drainage is the primary treatment, and for simple abscesses this may be adequate alone; however, antibiotic therapy is mandatory when there is extensive disease, systemic illness, multiple sites of infection, immunosuppression, difficult-to-drain locations (face, hand, genitalia), or failure to respond to drainage alone. 1

Initial Management: Drainage First

• Surgical debridement and drainage of abscesses is the mainstay of therapy and should be performed whenever feasible before or concurrent with antibiotic therapy. 1, 2
• Obtain cultures from purulent drainage before starting antibiotics to confirm MRSA and guide definitive therapy. 1
• For simple abscesses or boils without surrounding cellulitis or systemic symptoms, incision and drainage alone may be adequate without antibiotics. 1

When Antibiotics Are Required

Antibiotic therapy is mandatory for MRSA wound infections with any of the following features: 1

• Severe or extensive disease involving multiple sites
• Rapid progression with associated cellulitis
• Signs of systemic illness (fever, tachycardia, hypotension)
• Immunosuppression or significant comorbidities
• Extremes of age (very young or elderly)
• Abscess in difficult-to-drain locations (face, hand, genitalia)
• Associated septic phlebitis
• Lack of response to incision and drainage alone

Outpatient Oral Antibiotic Options

For outpatient treatment of purulent MRSA wound infections requiring antibiotics, the first-line options are: 1, 2

• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily 1, 3
• Doxycycline 100 mg twice daily 1, 3
• Clindamycin 300-450 mg three times daily (only if local MRSA resistance rates are <10%) 1, 2

Important Considerations for Oral Therapy

• TMP-SMX and tetracyclines have excellent MRSA coverage but poorly defined activity against β-hemolytic streptococci. 3
• If coverage for both MRSA and streptococci is needed (purulent cellulitis with surrounding erythema), use either clindamycin alone OR combine TMP-SMX or doxycycline with a β-lactam such as amoxicillin. 1, 3
• Linezolid 600 mg twice daily is highly effective but significantly more expensive and should be reserved for cases where other options have failed or are contraindicated. 1
• Never use rifampin as monotherapy or add it routinely to other antibiotics for wound infections, as resistance develops rapidly and there is no evidence of benefit. 1, 3

Inpatient IV Antibiotic Options

For hospitalized patients with complicated MRSA wound infections (deeper soft-tissue infections, surgical/traumatic wounds, major abscesses, infected ulcers/burns), the following IV options are recommended: 1

• Vancomycin 15-20 mg/kg IV every 8-12 hours (gold standard for hospitalized patients) 1, 2
• Linezolid 600 mg IV twice daily 1, 4
• Daptomycin 4 mg/kg IV once daily 1, 5
• Telavancin 10 mg/kg IV once daily 1
• Clindamycin 600 mg IV three times daily (if local resistance <10%) 1

Evidence for IV Agents

• Linezolid demonstrated 79% cure rates for MRSA skin and skin structure infections in clinical trials, with 90% cure rates in complicated infections when combined with appropriate surgical management. 4
• Daptomycin showed 44% success rates in complicated MRSA bacteremia/endocarditis trials, though this included deep-seated infections requiring surgical intervention. 5
• Vancomycin remains acceptable but has limitations including poor tissue penetration, slow bacterial killing, and emerging reduced susceptibility in some MRSA strains. 6, 7

Treatment Duration

• 5-10 days of therapy for uncomplicated MRSA wound infections 1, 2
• 7-14 days for complicated infections 1, 2
• Clinical reassessment within 48-72 hours is essential to ensure appropriate response to therapy. 2
• If no improvement occurs within 48-72 hours, reassess for undrained collections, consider alternative antibiotics, or escalate to IV therapy. 3

Critical Pitfalls to Avoid

• Never use β-lactam antibiotics alone when MRSA is confirmed or suspected, as they have no activity against methicillin-resistant organisms. 3
• Failure to drain associated abscesses leads to treatment failure regardless of antibiotic choice. 2, 3
• Do not use clindamycin if local MRSA resistance rates exceed 10% or if inducible resistance is detected on susceptibility testing. 3
• TMP-SMX or tetracyclines without a β-lactam will miss streptococcal coverage if there is surrounding cellulitis. 3

Special Populations

Pediatric Patients

• Clindamycin 10-13 mg/kg/dose orally every 6-8 hours 2
• TMP-SMX 4-6 mg/kg/dose (trimethoprim component) orally every 12 hours 2
• Tetracyclines should not be used in children under 8 years of age. 2

Diabetic Foot Infections

• For mild diabetic wound infections with MRSA, use the same oral regimens as above. 1
• For moderate to severe diabetic foot infections with MRSA, use IV vancomycin, linezolid, or daptomycin plus appropriate Gram-negative coverage if needed. 1
• All diabetic foot infections require aggressive debridement and off-loading in addition to antibiotics. 4