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

Treatment of Infective Endocarditis

The recommended treatment for infective endocarditis requires 4-6 weeks of targeted antimicrobial therapy based on the causative organism, with specific antibiotic regimens determined by pathogen identification and susceptibility testing. 1

Diagnostic Approach

• Obtain at least 3 sets of blood cultures before initiating antibiotics
• Perform transthoracic echocardiography (TTE) as first-line imaging
• If TTE is negative or non-diagnostic with high clinical suspicion, proceed to transesophageal echocardiography (TEE) 2
• TEE is recommended as first-line diagnostic study for prosthetic valve endocarditis 1

Antimicrobial Therapy by Pathogen

Viridans Group Streptococci and S. bovis

• First-line treatment: 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 1, 2
• Alternative: Ceftriaxone 2g/day IV/IM in single dose for 4 weeks 1, 2
• For penicillin-allergic patients: Vancomycin 30 mg/kg/24h IV in 2 equally divided doses for 4 weeks 3
• Duration: 4 weeks for native valve, 6 weeks for prosthetic valve 1, 2

Enterococci

• Ampicillin 12g/24h IV in 6 equally divided doses plus gentamicin 3 mg/kg/24h IV/IM in 2-3 divided doses for 4-6 weeks 1
• For penicillin-allergic patients: Vancomycin plus gentamicin 3
• For multi-resistant strains: Daptomycin 10 mg/kg/day plus ampicillin 200 mg/kg/day IV 1

Staphylococci

• Methicillin-susceptible S. aureus (native valve): Nafcillin or oxacillin 12g/24h IV in 6 equally divided doses for 6 weeks 1, 4
• Methicillin-resistant S. aureus (MRSA): Vancomycin 30 mg/kg/24h IV in 2 equally divided doses for 6 weeks 1, 3
• Prosthetic valve staphylococcal endocarditis:
  • Oxacillin-susceptible: Nafcillin/oxacillin plus rifampin (900 mg/24h IV/PO in 3 divided doses) plus gentamicin for at least 6 weeks 1
  • Oxacillin-resistant: Vancomycin plus rifampin plus gentamicin for at least 6 weeks 1

HACEK Organisms

• Ceftriaxone 2g/24h IV/IM in single dose for 4 weeks (native valve) or 6 weeks (prosthetic valve) 1
• Alternatives: Ampicillin-sulbactam 12g/24h IV in 4 equally divided doses or ciprofloxacin for patients unable to tolerate cephalosporins 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 additional quinolones or cotrimoxazole based on susceptibility 1

Fungal Endocarditis

• Combined antifungal administration and surgical valve replacement 1
• Early surgical intervention is essential due to high mortality (>50%) 1

Blood Culture-Negative Endocarditis

• Empiric therapy based on likely pathogens while awaiting further diagnostic workup 1, 2
• For suspected Bartonella: Doxycycline plus gentamicin (doxycycline for 4 weeks, gentamicin for 2 weeks) 2
• For suspected Q fever (C. burnetii): Doxycycline plus hydroxychloroquine for >18 months 2

Empiric Therapy Before Organism Identification

• Native valve: Vancomycin plus ceftriaxone 2
• Prosthetic valve: Vancomycin, gentamicin, and rifampin 2

Duration of Therapy

• Native valve endocarditis: 4 weeks (6 weeks for S. aureus) 1
• Prosthetic valve endocarditis: At least 6 weeks 1
• Count days from first negative blood culture in cases with initially positive cultures 1

Monitoring During Treatment

• Daily clinical assessment
• Serial blood cultures until sterilization is documented
• Regular echocardiographic follow-up
• Monitor renal function and drug levels for gentamicin and vancomycin
  • Target trough levels: Gentamicin <1 mg/L, Vancomycin 10-15 μg/mL
  • Target peak levels: Gentamicin 10-12 mg/L, Vancomycin 30-45 μg/mL 2

Surgical Indications

• Heart failure due to valve dysfunction
• Uncontrolled infection despite appropriate antibiotics
• Large mobile vegetations (>10mm) with embolic risk
• Perivalvular abscess or fistula formation
• S. aureus prosthetic valve endocarditis
• Fungal endocarditis 2

Recent Evidence on Partial Oral Therapy

A 2019 study demonstrated that switching stable patients to oral antibiotics after at least 10 days of IV therapy was non-inferior to continued IV treatment for the full course 5. However, this approach should be limited to carefully selected patients who are clinically stable with good response to initial IV therapy.

Common Pitfalls to Avoid

• Delaying blood cultures before starting antibiotics
• Inadequate duration of therapy
• Failure to identify and address complications requiring surgical intervention
• Not adjusting antibiotic doses in patients with renal dysfunction
• Overlooking the need for follow-up echocardiography after treatment completion
• Neglecting to provide endocarditis prophylaxis education for future procedures

Remember that successful treatment requires a multidisciplinary approach involving cardiology, infectious disease, and cardiac surgery specialists to optimize outcomes and reduce mortality.