What is the common prophylaxis for subacute purulent endocarditis secondary to Methicillin-Sensitive Staphylococcus aureus (MSSA)?

Prophylaxis for Subacute Purulent Endocarditis Secondary to MSSA

For subacute purulent endocarditis caused by Methicillin-Sensitive Staphylococcus aureus (MSSA), the recommended prophylactic treatment is (flu)cloxacillin or oxacillin at 12 g/day IV in 4-6 divided doses for 4-6 weeks. 1

First-Line Treatment for Native Valve Endocarditis (NVE) due to MSSA

• For native valve endocarditis caused by MSSA, (flu)cloxacillin or oxacillin at 12 g/day IV in 4-6 divided doses is the treatment of choice for 4-6 weeks 1
• The addition of gentamicin is no longer recommended for native valve MSSA endocarditis as clinical benefit has not been demonstrated and there is increased risk of renal toxicity 1
• For uncomplicated infections, 4 weeks of therapy may be sufficient, while complicated infections (perivalvular abscess, metastatic infections) require at least 6 weeks of treatment 1

Alternative Regimens for Penicillin-Allergic Patients

• For patients with non-anaphylactic penicillin allergy, cefazolin (6 g/day IV in 3 doses) is recommended 1
• For patients with severe penicillin allergy, vancomycin (30-60 mg/kg/day IV in 2-3 doses) is recommended for 4-6 weeks 1
• Daptomycin (10 mg/kg/day IV once daily) is an alternative therapy that may be superior to vancomycin for MSSA bacteremia with vancomycin MIC >1 mg/L 1
• Another alternative regimen includes high-dose cotrimoxazole (sulfamethoxazole 4800 mg/day and trimethoprim 960 mg/day IV in 4-6 doses) with clindamycin (1800 mg/day IV in 3 doses) for 1 week IV followed by 5 weeks oral therapy 1

Treatment for Prosthetic Valve Endocarditis (PVE) due to MSSA

• For prosthetic valve endocarditis, a more aggressive approach is required with combination therapy 1
• The recommended regimen is (flu)cloxacillin or oxacillin (12 g/day IV in 4-6 doses) plus rifampin (900-1200 mg IV or orally in 2-3 divided doses) for at least 6 weeks, with gentamicin (3 mg/kg/day IV or IM in 1-2 doses) added for the first 2 weeks 1
• Starting rifampin 3-5 days after initiating the primary antibiotic has been suggested by some experts to avoid antagonistic effects against replicating bacteria 1

Important Considerations and Monitoring

• Blood cultures should be obtained to confirm clearance of bacteremia 1
• For brain abscess complicating MSSA IE, nafcillin is preferred over cefazolin due to better blood-brain barrier penetration 1
• Serum drug levels should be monitored when using vancomycin, with target trough levels of 15-20 mg/L 1
• Early surgical intervention should be considered in cases with complications such as heart failure, persistent bacteremia, or local spread of infection 1

Duration of Therapy

• For native valve endocarditis: 4-6 weeks of therapy is recommended 1
• For prosthetic valve endocarditis: minimum of 6 weeks of therapy is recommended 1
• Therapy should be continued for at least 48 hours after the patient becomes afebrile, asymptomatic, and cultures are negative 2

Common Pitfalls to Avoid

• Avoid adding gentamicin to nafcillin/oxacillin for native valve MSSA endocarditis as it increases nephrotoxicity without improving outcomes 1
• Do not use vancomycin for MSSA if β-lactams can be used, as outcomes are inferior with vancomycin 1
• Avoid using clindamycin as monotherapy for MSSA endocarditis as it has been associated with relapse 1
• Do not use penicillin alone for MSSA as most strains are resistant, even if initially reported as susceptible 1

Following these evidence-based guidelines will optimize outcomes for patients with subacute purulent endocarditis due to MSSA, focusing on reducing mortality and morbidity while improving quality of life.