Treatment of MRSA Infections
For MRSA skin and soft tissue infections, incision and drainage is the primary treatment, with antibiotics added for severe/extensive disease, systemic illness, or surrounding cellulitis; first-line oral options include trimethoprim-sulfamethoxazole, doxycycline, or clindamycin (if local resistance <10%), while vancomycin or daptomycin are preferred for bacteremia and endocarditis. 1
Skin and Soft Tissue Infections (SSTIs)
Simple Abscesses
- Incision and drainage alone is adequate for simple abscesses without antibiotics 1, 2
- Obtain cultures from purulent drainage before starting antibiotics to confirm MRSA and guide therapy 2, 3
When to Add Antibiotics to Drainage
Add antibiotics when any of the following are present: 1, 2
- Severe or extensive disease involving multiple sites
- Rapid progression with surrounding cellulitis
- Signs of systemic illness (fever, tachycardia, hypotension)
- Immunosuppression or significant comorbidities
- Extremes of age (very young or elderly)
- Difficult-to-drain locations (face, hand, genitalia)
- Lack of response to drainage alone
Outpatient Oral Antibiotic Options
For purulent cellulitis (cellulitis with purulent drainage): 1, 3
- Trimethoprim-sulfamethoxazole (TMP-SMX): 1-2 double-strength tablets orally twice daily 1, 4
- Doxycycline: 100 mg orally twice daily 1, 2
- Minocycline: 200 mg loading dose, then 100 mg orally twice daily 3
- Clindamycin: 300-450 mg orally three times daily (only if local resistance <10%) 1, 3
- Linezolid: 600 mg orally twice daily (more expensive but highly effective) 1, 3
Important caveat: TMP-SMX and tetracyclines do not adequately cover beta-hemolytic streptococci 1, 3. If coverage for both MRSA and streptococci is needed, use clindamycin alone OR combine TMP-SMX/tetracycline with a beta-lactam (amoxicillin) 1
Treatment duration: 5-10 days for uncomplicated infections 1, 2, 3
Hospitalized Patients with Complicated SSTIs
Intravenous options for severe infections: 1
- Vancomycin: 15-20 mg/kg/dose IV every 8-12 hours 3
- Daptomycin: 4 mg/kg/dose IV once daily 1, 5
- Linezolid: 600 mg IV/PO twice daily 1, 6
- Telavancin: 10 mg/kg/dose IV once daily 1
Treatment duration: 7-14 days for complicated infections 1, 3
MRSA Bacteremia and Endocarditis
Uncomplicated Bacteremia
Definition: Positive blood cultures with ALL of the following: 1
- Endocarditis excluded
- No implanted prostheses
- Follow-up cultures at 2-4 days negative for MRSA
- Fever resolves within 72 hours of effective therapy
- No metastatic infection sites
Treatment options: 1
- Vancomycin (preferred) 1
- Daptomycin: 6 mg/kg/dose IV once daily 1
- Some experts recommend higher doses of 8-10 mg/kg/dose IV once daily 1
Duration: Minimum 2 weeks 1
Complicated Bacteremia
Definition: Patients NOT meeting all criteria for uncomplicated bacteremia 1
Treatment: Same antibiotic options as uncomplicated bacteremia 1
Duration: 4-6 weeks depending on extent of infection 1
Infective Endocarditis
Treatment options: 1
- Vancomycin IV for 6 weeks 1
- Daptomycin: 6 mg/kg/dose IV once daily for 6 weeks 1
- Some experts recommend 8-10 mg/kg/dose IV once daily 1
Critical management steps: 1
- Obtain blood cultures 2-4 days after initial positive cultures to document clearance 1
- Perform echocardiography on ALL adult patients with bacteremia; transesophageal echocardiography (TEE) preferred over transthoracic (TTE) 1
- Identify and eliminate/debride source of infection 1
- Remove infected intravascular or prosthetic devices (failure to remove increases relapse and mortality) 1
Valve replacement surgery indicated for: 1
- Large vegetation >10 mm
- Embolic event during first 2 weeks of therapy
- Severe valvular insufficiency or perforation
- Decompensated heart failure
- Perivalvular or myocardial abscess
- New heart block
- Persistent fevers or bacteremia
What NOT to Do for Bacteremia/Endocarditis
- Do NOT add gentamicin to vancomycin (does not improve outcomes) 1
- Do NOT add rifampin to vancomycin (does not improve outcomes, increases toxicity and resistance) 1
Pediatric Considerations
Antibiotic dosing for children: 4, 3
- Clindamycin: 10-13 mg/kg/dose orally every 6-8 hours (maximum 40 mg/kg/day) 4
- TMP-SMX: 4-6 mg/kg/dose (trimethoprim component) orally every 12 hours 3
- Vancomycin: Preferred IV agent for severe infections 2
Important restriction: Tetracyclines (doxycycline, minocycline) should NOT be used in children under 8 years of age 4, 3
For pediatric bacteremia: Age-dependent daptomycin dosing showed clinical success of 88% in patients aged 1-17 years: 5
- Adolescents (12-17 years): 7 mg/kg once daily
- Children (7-11 years): 9 mg/kg once daily
- Children (2-6 years): 12 mg/kg once daily
MRSA in Urine
Assessment: Distinguish between asymptomatic bacteriuria, uncomplicated UTI, or complicated UTI with bacteremia 4
Treatment options: 4
- TMP-SMX: 1-2 double-strength tablets orally twice daily
- Clindamycin: 300-450 mg orally three times daily
Duration: 4
- 7-14 days for uncomplicated bacteriuria without systemic symptoms
- 2-4 weeks for complicated bacteriuria or concurrent bacteremia
Follow-up: Obtain urine cultures 48-72 hours after starting therapy to document clearance 4
Prevention of Recurrence
Basic hygiene measures: 4, 2, 3
- Keep draining wounds covered with clean, dry bandages
- Regular handwashing with soap and water or alcohol-based gel
- Avoid sharing personal items
Decolonization: Consider for patients with recurrent MRSA infections despite optimizing wound care and hygiene 4, 2
- Mupirocin (nasal application)
- Chlorhexidine (body wash)
Common Pitfalls to Avoid
- Never use beta-lactam antibiotics alone for MRSA (they are ineffective by definition) 2
- Never fail to drain abscesses when present (antibiotics alone will fail regardless of choice) 2
- Never use rifampin as monotherapy or adjunctive therapy for SSTIs (not recommended) 1, 2
- Never use daptomycin for pneumonia (it is inactivated by pulmonary surfactant) 7