What is the first line treatment for endocarditis?

First-Line Treatment of Infective Endocarditis

The first-line treatment for infective endocarditis depends on the causative organism, with penicillin-susceptible viridans streptococci or S. bovis typically treated with 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, while MSSA endocarditis requires nafcillin or oxacillin (12g/24h IV in 6 equally divided doses) for 6 weeks, and MRSA requires vancomycin (30 mg/kg/24h IV in 2 equally divided doses) for 6 weeks. 1

Treatment Based on Causative Organism

Streptococcal Endocarditis

• Penicillin-susceptible viridans streptococci or S. bovis:
  • 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)
  • Duration: 4 weeks 1
  • Alternative: Ceftriaxone 2g once daily IV/IM for 4 weeks (especially for outpatient therapy in stable patients) 2, 1

Enterococcal Endocarditis

• Penicillin-susceptible enterococci:
  • Ampicillin (12g/24h IV in 6 equally divided doses) OR
  • Penicillin G (18-30 million U/24h IV in 6 equally divided doses)
  • PLUS Gentamicin (3 mg/kg/24h IV/IM in 3 equally divided doses)
  • Duration: 4-6 weeks 2, 1
  • Note: 4-week therapy for symptoms ≤3 months; 6-week therapy for symptoms >3 months 2

Staphylococcal Endocarditis

• Methicillin-susceptible S. aureus (MSSA):

  • Nafcillin or oxacillin (12g/24h IV in 6 equally divided doses)
  • Duration: 6 weeks 1
  • Consider adding gentamicin for first 3-5 days to accelerate clearing of bacteremia 3

• Methicillin-resistant S. aureus (MRSA):

  • Vancomycin (30 mg/kg/24h IV in 2 equally divided doses)
  • Duration: 6 weeks 2, 1
  • Adjust vancomycin to achieve 1-hour serum concentration of 30-45μg/ml and trough concentration of 10-15μg/ml 2

HACEK Microorganisms

• Ceftriaxone (2g per 24h IV/IM in 1 dose)
• Duration: 4 weeks 2
• Alternatives: Ampicillin-sulbactam or ciprofloxacin 2

Special Considerations for Prosthetic Valve Endocarditis

Early Prosthetic Valve Endocarditis (<1 year post-surgery)

• Vancomycin (30 mg/kg/24h IV in 2 equally divided doses)
• PLUS Gentamicin (3 mg/kg/24h IV/IM in 3 equally divided doses) for 2 weeks
• PLUS Cefepime (6g/24h IV in 3 equally divided doses)
• PLUS Rifampin (900 mg/24h PO/IV in 3 equally divided doses)
• Duration: 6 weeks 1

Late Prosthetic Valve Endocarditis (>1 year post-surgery)

• Same as native valve endocarditis with addition of rifampin 1

Treatment Duration

• Native valve endocarditis with symptoms <3 months: Minimum 4 weeks
• Native valve endocarditis with symptoms >3 months: 6 weeks
• Prosthetic valve endocarditis: Minimum 6 weeks 1

Monitoring During Treatment

• Daily clinical assessment
• Serial blood cultures until sterilization is documented
• Regular echocardiographic follow-up
• Monitoring of renal function
• Drug level monitoring:
  • Gentamicin: Trough levels <1 mg/L, peak levels 10-12 mg/L
  • Vancomycin: Trough levels 10-15 μg/mL, peak levels 30-45 μg/mL 1

Indications for Surgical Intervention

• Life-threatening congestive heart failure or cardiogenic shock
• Uncontrolled infection despite appropriate antibiotic therapy
• Persistent positive blood cultures
• Prosthetic valve infection
• S. aureus prosthetic valve endocarditis
• Fungal endocarditis
• Persistent vegetations >10mm after ≥1 embolic episodes 1

Important Caveats

• Early consultation with infectious disease specialists is strongly recommended
• Blood cultures should be obtained before initiating antibiotics whenever possible
• For empiric therapy before organism identification, consider combination therapy with aqueous penicillin G, nafcillin, and gentamicin 4
• Outpatient parenteral antibiotic therapy may be considered for stable patients who are compliant and capable of managing technical aspects 2
• Vancomycin should be reserved for patients with penicillin allergy or infections caused by resistant organisms 5, 3