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Infective endocarditis
Endocarditis is diagnosed by combining blood cultures and echocardiography (the Duke criteria), treated with prolonged intravenous antibiotics chosen by organism, and operated on when there is heart failure, uncontrolled infection or a risk of embolism.
Why it matters in the exam
Questions usually present prolonged fever with a new murmur and ask for the first step — at least three sets of blood cultures before antibiotics and an echocardiogram (TTE, then TEE). Candidates are asked which organism fits which story: Staphylococcus aureus in people who inject drugs (usually the tricuspid valve) and in healthcare-associated infection; viridans streptococci after dental work; Streptococcus gallolyticus (formerly bovis), which requires a colonoscopy; enterococci in older patients; and Coxiella burnetii (Q fever), Bartonella and HACEK when cultures are negative.
Other subjects: the indications for surgery, the duration of treatment (4–6 weeks for a native valve, at least 6 weeks for a prosthetic valve), Enterococcus faecalis treated with ampicillin plus ceftriaxone, and prophylaxis before dental procedures — intended only for high-risk patients: anyone with an artificial valve or with artificial material left after a valve repair, anyone who has had endocarditis before, and certain congenital heart diseases. Mitral valve prolapse, a bicuspid valve and hypertrophic cardiomyopathy are not indications for prophylaxis.
Key points
- Diagnosis: blood cultures (3 sets before antibiotics) and echocardiography, by the Duke criteria.
- S. aureus is the most common; viridans after dental work; S. gallolyticus — colonoscopy.
- Treatment: 4–6 weeks for a native valve, at least 6 weeks for a prosthetic one; E. faecalis — ampicillin with ceftriaxone.
- Surgery: heart failure, uncontrolled infection, large vegetation with embolism.
- Dental prophylaxis only at high risk: amoxicillin 2 g.
Summary table
| Item | The rule | Details | Trap |
|---|---|---|---|
| Diagnosis (Duke) | Definite: 2 major criteria, or 1 major and 3 minor, or 5 minor | Major: positive blood cultures for a typical organism; a finding on echo or PET-CT | Take at least 3 culture sets before antibiotics |
| Organisms | S. aureus — people who inject drugs and most common overall; viridans — after dental work | S. gallolyticus — colonoscopy | Culture-negative: Coxiella, Bartonella, HACEK |
| Antibiotics | Susceptible S. aureus: cloxacillin or cefazolin; resistant: vancomycin or daptomycin | E. faecalis: ampicillin with ceftriaxone | Native valve 4–6 weeks; prosthetic at least 6 weeks |
| Surgery | Heart failure, abscess or persistent bacteraemia, fungus or resistant organism | Vegetation of 10 mm or more with embolism | Heart failure is the most urgent indication |
| Prophylaxis before dental work | Only at high risk: prosthetic valve, previous endocarditis, certain congenital diseases | Amoxicillin 2 g orally 30–60 minutes before | Not for prolapse, not for a bicuspid valve |
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Sources
- ESC Guidelines for the management of endocarditis, 2023 — Diagnosis (modified Duke criteria), antibiotic therapy, surgery and prophylaxis
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Infective Endocarditis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.