Empirical Antibiotic Therapy for Staphylococcus Bacteremia
For empirical treatment of Staphylococcus bacteremia, vancomycin is recommended in healthcare settings with elevated prevalence of methicillin-resistant Staphylococcus aureus (MRSA), while flucloxacillin (or other antistaphylococcal penicillins) should be used when methicillin-susceptible Staphylococcus aureus (MSSA) is confirmed or highly likely. 1
Initial Empirical Therapy Considerations
- Vancomycin is the recommended empirical therapy in healthcare settings with high MRSA prevalence, pending culture and susceptibility results 1
- For institutions where MRSA isolates have vancomycin minimum inhibitory concentration (MIC) values >2 μg/mL, alternative agents such as daptomycin should be considered 1
- Flucloxacillin (or other antistaphylococcal penicillins like nafcillin or oxacillin) is the preferred treatment once methicillin-susceptibility is confirmed 2, 3
- Empirical combination of vancomycin plus a β-lactam may be beneficial while awaiting susceptibility results, as studies suggest this combination may shorten the duration of bacteremia 4, 5
Therapy Based on Susceptibility Results
For MSSA Bacteremia:
- Switch to flucloxacillin (or other antistaphylococcal penicillins) once susceptibility is confirmed 2, 3
- Continuing vancomycin for MSSA bacteremia is associated with 2-3 times higher risk of morbidity and mortality compared to antistaphylococcal penicillins 5
- Even de-escalation from empirical vancomycin to definitive β-lactam therapy appears inferior to initial β-lactam therapy 5
For MRSA Bacteremia:
- Continue vancomycin therapy if the organism is susceptible (MIC ≤2 μg/mL) 1
- For MRSA with vancomycin MIC >2 μg/mL, consider daptomycin 6 mg/kg/dose IV once daily 1
- Linezolid should not be used for empirical therapy of suspected bacteremia 1
Duration of Therapy
- For uncomplicated bacteremia: minimum 2 weeks of therapy 1
- For complicated bacteremia (persistent positive blood cultures, metastatic infection): 4-6 weeks of therapy 1
- Day 1 of therapy is considered the first day on which negative blood culture results are obtained 1
Additional Management Considerations
- Obtain follow-up blood cultures 2-4 days after initial positive cultures to document clearance of bacteremia 1
- Perform echocardiography to rule out endocarditis in all adult patients with S. aureus bacteremia 1, 3
- Identify and remove any potential source of infection (e.g., intravascular catheters, drainage of abscesses) 3
- For catheter-related S. aureus bacteremia, catheter removal is strongly recommended 1
Common Pitfalls to Avoid
- Continuing vancomycin for MSSA bacteremia after susceptibility results are available - this is associated with worse outcomes 5
- Using linezolid empirically for bacteremia - this is not recommended 1
- Failing to obtain follow-up blood cultures to document clearance of bacteremia 1
- Inadequate source control, which is critical for successful treatment 3
- Insufficient duration of therapy, especially for complicated infections 1
By following these evidence-based recommendations, clinicians can optimize outcomes for patients with Staphylococcus bacteremia while minimizing the risk of treatment failure and antimicrobial resistance.