What is the treatment for Gram-positive bacteremia?

Treatment of Gram-Positive Bacteremia

For Gram-positive bacteremia, initial empiric therapy should include vancomycin for MRSA coverage, with prompt de-escalation to a β-lactam (cefazolin or antistaphylococcal penicillin) once methicillin-susceptible Staphylococcus aureus (MSSA) is confirmed. 1, 2

Initial Empiric Treatment

Staphylococcus aureus Bacteremia

• First-line empiric therapy:
  • Vancomycin (15-20 mg/kg IV q8-12h, adjusted for renal function) 1
  • Consider adding a β-lactam (nafcillin, oxacillin, or cefazolin) empirically while awaiting susceptibility results 3
• Once susceptibilities are known:
  • For MSSA: De-escalate to cefazolin or antistaphylococcal penicillin (nafcillin/oxacillin) 1, 2
  • For MRSA: Continue vancomycin or switch to daptomycin (6-10 mg/kg IV daily) 4, 5

Coagulase-Negative Staphylococci (CNS)

• Initial therapy: Vancomycin 1
• Duration: 5-7 days after defervescence for uncomplicated cases 1
• Catheter management: May retain long-term catheters with appropriate systemic and antibiotic lock therapy if patient is stable 1

Enterococcal Bacteremia

• Initial therapy: Ampicillin for susceptible strains; vancomycin for resistant strains 1
• For VRE: Linezolid (600 mg IV/PO q12h), daptomycin, or quinupristin-dalfopristin 4, 6
• Consider combination therapy with gentamicin and ampicillin when catheter is retained 1

Catheter-Related Bloodstream Infections (CRBSI)

Catheter Management

1. S. aureus CRBSI:

   • Remove non-tunneled catheters 1
   • For tunneled catheters, remove if there is tunnel/exit site infection, persistent bacteremia, or evidence of metastatic infection 1

2. CNS CRBSI:

   • May attempt catheter salvage if patient is stable 1
   • Success rates of 46-93% reported for catheter retention 1
   • Higher risk of recurrence if catheter is retained, particularly with port systems 1

3. Candida CRBSI:

   • Always remove catheter 1

Antibiotic Lock Therapy

• Consider for salvaging "highly needed" infected catheters 1
• Options include vancomycin, teicoplanin, daptomycin, or aminoglycosides with heparin 1
• Duration: 10-14 days 1

Treatment Duration

• Uncomplicated S. aureus bacteremia: Minimum 14 days 1, 4
• Complicated S. aureus bacteremia (endocarditis, metastatic infection): 4-6 weeks 4
• CNS bacteremia: 5-7 days after defervescence 1
• Enterococcal bacteremia: 7-14 days for uncomplicated cases 1

Special Considerations

Diagnostic Evaluation

• For S. aureus bacteremia:
  • Transthoracic echocardiography for all patients 2
  • Transesophageal echocardiography for high-risk patients (persistent bacteremia, fever, metastatic infection, implanted cardiac devices) 2
  • Additional imaging based on symptoms and signs of metastatic infection 2

Common Pitfalls to Avoid

1. Delayed appropriate therapy: Mortality increases when effective antimicrobial therapy is delayed beyond 48 hours 7
2. Inadequate vancomycin dosing: For S. aureus bacteremia, ensure vancomycin doses ≥2.0 g/day to maintain therapeutic levels 7
3. Failure to de-escalate: Continuing vancomycin for MSSA bacteremia leads to 2-3 times higher risk of morbidity and mortality compared to β-lactam therapy 3, 8
4. Missing metastatic foci: Failure to identify and address metastatic infections can lead to treatment failure and relapse 2
5. Inadequate source control: Failure to remove infected devices or drain abscesses when indicated 2

Emerging Options

• Linezolid: Alternative to vancomycin for MRSA bacteremia, particularly in pneumonia 1, 6
• Daptomycin: Non-inferior to vancomycin for S. aureus bacteremia 5
• Ceftobiprole: Emerging option for MRSA bacteremia 2

By following these evidence-based guidelines and avoiding common pitfalls, mortality and morbidity from Gram-positive bacteremia can be significantly reduced through prompt, appropriate antimicrobial therapy and proper source control.