Staphylococcus aureus Management

Identification and Antibiotic Coverage

Oxacillin susceptibility is the definitive marker that excludes MRSA, as stated by the American Heart Association 1, 2, 3
The presence of oxacillin susceptibility confirms MSSA, according to the European Society of Cardiology 4
Antistaphylococcal penicillins (nafcillin, oxacillin) and first-generation cephalosporins (cefazolin) are specifically designed to resist staphylococcal beta-lactamases, as recommended by the American College of Cardiology 1, 2
Piperacillin-tazobactam has inadequate anti-staphylococcal activity compared to antistaphylococcal penicillins or first-generation cephalosporins, as noted by the Infectious Diseases Society of America 6
Beta-lactam antibiotics are not interchangeable for S. aureus, with studies demonstrating superior outcomes with beta-lactams specifically designed for staphylococci, according to the Clinical Infectious Diseases journal 7
For MSSA bacteremia, the European Society of Cardiology recommends using nafcillin/oxacillin 8-12 g/24h IV divided every 4-6 hours or cefazolin 4, 5
Piperacillin-tazobactam should not be considered adequate monotherapy for documented S. aureus infections, as stated by the Clinical Infectious Diseases journal 6

Antifungal therapy should only be initiated when there is microbiologic or clinical evidence of fungal infection, as recommended by the American Heart Association 1, 2, 3
Negative blood cultures for fungi indicate no empiric antifungal therapy is needed, according to the European Society of Cardiology 1, 4
Indications for antifungal therapy include positive fungal cultures, high clinical suspicion with risk factors, and persistent fever despite appropriate antibacterial therapy in high-risk patients, as noted by the Clinical Infectious Diseases journal 1, 6
For complicated bacteremia, the American College of Cardiology recommends 4-6 weeks of therapy 1, 5
Cefazolin is equally effective for most MSSA infections, though nafcillin/oxacillin is preferred for CNS involvement due to better blood-brain barrier penetration, as stated by the American Heart Association 1, 2