What is the recommended treatment for a patient diagnosed with endocarditis?

Treatment of Infective Endocarditis

The recommended treatment for infective endocarditis requires targeted antimicrobial therapy based on the causative organism, with a duration of 4-6 weeks, combined with surgical intervention when indicated for complications such as heart failure, uncontrolled infection, or large vegetations with embolic events. 1, 2

Antimicrobial Therapy by Pathogen

Streptococcal Endocarditis

• Penicillin-susceptible viridans streptococci or S. bovis:
  • First-line: Aqueous crystalline penicillin G (18-30 million U/24h IV in 6 equally divided doses) or ampicillin (12g/24h IV in 6 equally divided doses) for 4 weeks 2
  • Alternative: Ceftriaxone 2g/day IV/IM in 1 dose for 4 weeks 1
  • For prosthetic valve: Extend treatment to 6 weeks 2

Staphylococcal Endocarditis

• Methicillin-susceptible S. aureus (native valve):

  • Nafcillin or oxacillin 12g/24h IV in 6 equally divided doses for 6 weeks 1, 3
  • Alternative for penicillin-allergic patients: Cefazolin or vancomycin 1

• Methicillin-resistant S. aureus:

  • Vancomycin 30mg/kg/24h IV in 2 equally divided doses for 6 weeks 1, 4
  • Target vancomycin trough: 10-15μg/ml; peak: 30-45μg/ml 1

• Prosthetic valve staphylococcal endocarditis:

  • Combination therapy with:
    • Nafcillin/oxacillin (for MSSA) or vancomycin (for MRSA)
    • Plus rifampin 900mg/24h IV/PO in 3 equally divided doses
    • Plus gentamicin 3mg/kg/24h IV/IM in 2-3 divided doses
  • Duration: At least 6 weeks 1

Enterococcal Endocarditis

• Penicillin-susceptible enterococci:

  • Ampicillin 12g/24h IV in 6 doses plus gentamicin 3mg/kg/24h IV/IM in 2-3 doses for 4-6 weeks 1, 2
  • Monitor gentamicin levels and renal function closely

• Vancomycin-resistant enterococci:

  • Daptomycin 10mg/kg/day plus ampicillin 200mg/kg/day IV in 4-6 doses 1, 5
  • Alternative: Linezolid 2×600mg/day IV/PO for ≥8 weeks 1

HACEK Microorganisms

• First-line: Ceftriaxone 2g/day IV for 4 weeks (native valve) or 6 weeks (prosthetic valve) 1
• Alternatives:
  • Ampicillin-sulbactam 12g/24h IV in 4 equally divided doses for 4 weeks 1
  • Ciprofloxacin (if unable to tolerate beta-lactams) 1

Non-HACEK Gram-Negative Bacteria

• Early surgery plus long-term (at least 6 weeks) therapy with bactericidal combinations of beta-lactams and aminoglycosides 1
• Consider adding quinolones or cotrimoxazole based on susceptibility 1

Fungal Endocarditis

• Combination of antifungal therapy and surgical valve replacement 1
• Mortality is very high (>50%) despite treatment 1

Culture-Negative Endocarditis

• Bartonella spp.: Doxycycline (200mg/24h) plus gentamicin for 2 weeks 2
• Coxiella burnetii (Q fever): Doxycycline plus hydroxychloroquine for >18 months 2
• Brucella spp.: Doxycycline (200mg/24h) plus cotrimoxazole (960mg/12h) plus rifampin (300-600mg/24h) for ≥3-6 months 1, 2

Surgical Indications

Surgery should be considered for:

1. Heart failure due to valve dysfunction
2. Uncontrolled infection (persistent bacteremia, abscess, prosthetic valve infection)
3. Prevention of embolic events with large vegetations (>10mm) after ≥1 embolic episodes
4. Prosthetic valve endocarditis, especially with S. aureus or fungal pathogens 2

Monitoring During Treatment

• Daily clinical assessment
• Serial blood cultures until sterilization
• Regular echocardiographic follow-up
• Monitor renal function
• Drug level monitoring for gentamicin and vancomycin 2

Pitfalls and Caveats

1. Delayed diagnosis can lead to increased mortality - obtain at least 3 sets of blood cultures before starting antibiotics
2. Inadequate dosing - ensure bactericidal concentrations are achieved
3. Failure to identify complications requiring surgery - perform regular echocardiography
4. Premature discontinuation of therapy - complete the full 4-6 week course
5. Overlooking prosthetic valve involvement - requires longer treatment and often combination therapy
6. Aminoglycoside toxicity - monitor levels and renal function closely
7. Incomplete follow-up - perform echocardiography at completion of therapy to establish new baseline 1, 2

Recent evidence suggests that in stable patients with left-sided endocarditis, switching from IV to oral antibiotics after initial improvement (at least 10 days of IV therapy) may be a viable option, potentially allowing outpatient management 6.