23 Sept 2026 · Case #018
Infective endocarditis
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Diagnosis
Infective endocarditis
First-line treatment
IV benzylpenicillin (penicillin G) with gentamicin
How the diagnosis is reached
A murmur that has changed character is what turns six weeks of vague fevers into an emergency. His old records describe a soft mid-systolic click, the sound of mitral valve prolapse; what he has now is a pansystolic murmur radiating to the axilla, severe regurgitation through a leaflet eaten away since. Being twice labelled a viral illness is the ordinary history here, and the molar extracted two months ago is the portal of entry for viridans group streptococci, low-virulence mouth commensals that settle on valves already abnormal. The peripheral stigmata are immune and embolic phenomena of persistent bacteraemia: splinter haemorrhages, painless Janeway lesions, a Roth spot. Microscopic haematuria with a sterile urine reflects immune-complex glomerulonephritis, not urinary infection, and a positive rheumatoid factor in this setting is another immune-complex phenomenon rather than evidence of rheumatoid arthritis. He meets both modified Duke major criteria, persistently positive cultures with a typical organism across three separate sets and echocardiographic vegetation, which is sufficient for a definite diagnosis. Two practical points. Cultures must come from separate sites before antibiotics, since prior antibiotics are the commonest cause of culture-negative endocarditis. And a normal transthoracic study does not exclude endocarditis: sensitivity is roughly 60–70%, so transoesophageal imaging is required when suspicion is high. A penicillin MIC of 0.06 mg/L puts the organism in the fully susceptible range, which decides the regimen: intravenous benzylpenicillin for four weeks alone, or two weeks with gentamicin for synergy, the shorter course being reasonable because the disease is uncomplicated native-valve with no annular abscess. Ceftriaxone is the outpatient alternative. Surgery is reserved for heart failure, uncontrolled infection, abscess or recurrent embolism, and the perforated leaflet with severe regurgitation is why this valve needs watching for the first of those.
Key clinical clues
- Six weeks of fever, night sweats and weight loss following a dental extraction
- A new pansystolic murmur where old records described only a click
- Splinter haemorrhages, Janeway lesions, Roth spot and splenomegaly
- Microscopic haematuria with sterile urine, immune-complex glomerulonephritis
- Three separate positive culture sets plus vegetation on TOE (both Duke major criteria)
The case in full
Presenting complaint
Patient history
A 46-year-old man has six weeks of low-grade evening fevers, night sweats, aching muscles and 6 kg of weight loss, twice treated as a viral illness. He had a molar extracted two months ago, and was told as a teenager of a murmur needing no treatment.
Examination
Physical examination
He looks unwell and pale. A pansystolic murmur at the apex radiates to the axilla; his old records note only a soft mid-systolic click. There are splinter haemorrhages under three nails, non-tender macules on both palms, a spleen 3 cm below the costal margin, and a retinal haemorrhage with a pale centre.
| Parameter | Value | Reference |
|---|---|---|
| Temperature | 38.2 °CRef 36.1–37.5 | 36.1–37.5 |
| Heart rate | 98 bpmRef 60–100 | 60–100 |
| Blood pressure | 118/62 mmHg | – |
Blood count and inflammatory markers
Laboratory results
A blood count and inflammatory markers are sent.
| Parameter | Value | Reference |
|---|---|---|
| Hemoglobin | 9.8 g/dLRef 13.5–17.5 | 13.5–17.5 |
| Mean cell volume | 88 fLRef 80–100 | 80–100 |
| White blood cells | 12.4 ×10⁹/LRef 4.5–11.0 | 4.5–11.0 |
| ESR | 88 mm/hRef <20 | <20 |
| C-reactive protein | 96 mg/LRef <5 | <5 |
| Rheumatoid factor | PositiveRef Negative | Negative |
Urinalysis
Laboratory results
Urine dipstick and microscopy are performed as part of the septic screen.
| Parameter | Value | Reference |
|---|---|---|
| Blood (dipstick) | 2+Ref Negative | Negative |
| Protein (dipstick) | 1+Ref Negative | Negative |
| Red cells (microscopy) | 40–50 /hpfRef <3 | <3 |
| Nitrites / leukocyte esterase | NegativeRef Negative | Negative |
| Urine culture | No growthRef No growth | No growth |
Blood cultures
Laboratory results
Three sets of blood cultures are drawn from separate sites more than an hour apart, before any antibiotics are given.
| Parameter | Value | Reference |
|---|---|---|
| Set 1 (time 0) | Positive at 34 hRef No growth | No growth |
| Set 2 (time +1 h) | Positive at 36 hRef No growth | No growth |
| Set 3 (time +6 h) | Positive at 38 hRef No growth | No growth |
| Organism | Viridans group StreptococcusRef No growth | No growth |
| Penicillin MIC | 0.06 mg/LRef Susceptible ≤0.12 | Susceptible ≤0.12 |
Echocardiography
Imaging
Transthoracic echocardiography is technically limited and reported as unremarkable. A transoesophageal study is then performed. It shows a 13 mm mobile, irregular echodensity on the atrial surface of the posterior mitral leaflet, moving independently of the leaflet through the cardiac cycle, with a small perforation and severe regurgitation through it. There is no abscess at the annulus.