What is the recommended treatment for an adult with a confirmed or strongly suspected MRSA infection, based on infection site and severity?

MRSA Treatment

For confirmed or suspected MRSA infections, vancomycin 15-20 mg/kg IV every 8-12 hours remains the first-line treatment for severe/hospitalized cases, while oral trimethoprim-sulfamethoxazole, doxycycline, or linezolid are appropriate for uncomplicated outpatient skin infections—but surgical drainage must be performed for any abscess regardless of antibiotic choice. 1

Initial Management: Source Control is Mandatory

Surgical drainage and debridement of abscesses must be performed whenever possible, regardless of antibiotic therapy. 1 For simple abscesses or furuncles, incision and drainage alone may be adequate without antibiotics, but additional antibiotics are recommended for more extensive infections. 1

• Obtain cultures of purulent drainage before starting antibiotics to confirm MRSA and guide definitive therapy. 1
• Clinical assessment to identify the source and extent of infection with elimination and/or debridement of other sites of infection should be conducted. 2

Antibiotic Selection by Infection Severity

Non-Severe Infections (Outpatient Management)

For uncomplicated MRSA skin and soft tissue infections that can be managed outpatient, oral options include: 1

• Trimethoprim-sulfamethoxazole (TMP-SMX) 4 mg/kg/dose (TMP component) twice daily 1
• Doxycycline 100 mg orally twice daily or minocycline 100 mg orally twice daily 1
• Clindamycin 600 mg orally three times daily—ONLY if local resistance rates are <10% 1
• Linezolid 600 mg orally twice daily 1

Critical pitfall: Clindamycin should only be used if local resistance rates are <10%, as resistance is common in many areas. 1

Severe or Complicated Infections (Hospitalization Required)

For hospitalized patients with severe MRSA infections: 1

• Vancomycin 15-20 mg/kg/dose IV every 8-12 hours is the first-line treatment, with target trough levels of 15-20 mg/L for serious infections 1, 3
• Daptomycin 6 mg/kg/dose IV once daily is an equally acceptable first-line alternative for complicated skin infections and bacteremia 1, 3
• Linezolid 600 mg IV/PO twice daily has excellent efficacy against MRSA skin infections and is specifically preferred for MRSA pneumonia due to superior lung penetration 1, 4
• Ceftaroline 600 mg IV every 12 hours is a newer option with proven efficacy 1

Critical pitfall: Daptomycin should NOT be used to treat MRSA pneumonia, as it is inactivated by pulmonary surfactant. 1 Use linezolid for pneumonia instead. 1

Site-Specific Considerations

MRSA Pneumonia

• Vancomycin or linezolid are the preferred agents. 2 Linezolid 600 mg IV twice daily is specifically preferred due to superior lung penetration. 1
• If empyema complicates pneumonia, antimicrobial therapy must be used in conjunction with drainage procedures. 2

MRSA Bacteremia and Endocarditis

For uncomplicated bacteremia (defined as: exclusion of endocarditis, no implanted prostheses, follow-up blood cultures negative at 2-4 days, defervescence within 72 hours, no metastatic sites): 2

• Vancomycin or daptomycin 6 mg/kg/dose IV once daily for at least 2 weeks 2, 1

For complicated bacteremia (patients not meeting above criteria): 2

• 4-6 weeks of therapy is recommended, depending on extent of infection 2, 1
• Some experts recommend higher daptomycin dosages at 8-10 mg/kg/dose IV once daily 2, 3

For infective endocarditis: 2

• Vancomycin or daptomycin 6 mg/kg/dose IV once daily for 6 weeks 2, 1
• Some experts recommend higher daptomycin dosages at 8-10 mg/kg/dose IV once daily 2

Essential monitoring for bacteremia: 2, 1

• Additional blood cultures 2-4 days after initial positive cultures and as needed thereafter to document clearance of bacteremia 2, 1
• Echocardiography (preferably transesophageal) is recommended for all adult patients with bacteremia 2, 1

Critical pitfalls to avoid: 2

• Addition of gentamicin to vancomycin is NOT recommended for bacteremia or native valve endocarditis 2
• Addition of rifampin to vancomycin is NOT recommended for bacteremia or native valve endocarditis 2

Duration of Treatment

Standard treatment durations: 1

• 5-10 days for uncomplicated skin infections 1
• 7-14 days for complicated skin and soft tissue infections 1
• At least 2 weeks for uncomplicated bacteremia 1
• 4-6 weeks for complicated bacteremia 1
• 6 weeks for endocarditis 1

Pediatric Considerations

• Vancomycin IV is the recommended first-line agent for children with MRSA infections. 1
• Clindamycin 10-13 mg/kg/dose IV every 6-8 hours can be used as empirical therapy if the clindamycin resistance rate is low (<10%), with transition to oral therapy if the strain is susceptible. 1
• Linezolid 600 mg PO/IV twice daily for children >12 years and 10 mg/kg/dose every 8 hours for children <12 years. 1

Prevention of Recurrence

Decolonization may be considered in selected cases if: 2, 1

• A patient develops recurrent SSTI despite optimizing wound care and hygiene measures 2, 1
• Ongoing transmission is occurring among household members or other close contacts despite optimizing wound care and hygiene measures 2, 1

Decolonization strategies include: 2, 1

• Nasal decolonization with mupirocin twice daily for 5-10 days 2, 1
• Topical body decolonization with antiseptic solution (e.g., chlorhexidine) for 5-14 days or dilute bleach baths 2, 1

Common Pitfalls to Avoid

• Beta-lactam antibiotics alone are inadequate for MRSA coverage, as MRSA is by definition resistant to these agents. 1
• Failure to drain abscesses when present leads to treatment failure regardless of antibiotic choice. 1
• Daptomycin should not be used for MRSA pneumonia as it is inactivated by pulmonary surfactant. 1
• Local resistance patterns should guide antibiotic selection, especially for clindamycin, which should only be used if local resistance rates are <10%. 1