Question

A 59-year-old man attends the acute medical unit with 4 days of fever, tiredness and mild breathlessness. He has longstanding poor oral hygiene and had a dental extraction around 2 weeks ago. His only regular medication is an antihypertensive.

He is febrile and tachycardic. Cardiac examination reveals an early diastolic murmur, best heard with the patient leaning forward in expiration along the left sternal border. There are painless erythematous macular lesions on the palms. Chest X-ray is normal and inflammatory markers are raised.

Which organism is most likely responsible?

A. Aggregatibacter actinomycetemcomitans
B. Methicillin-sensitive Staphylococcus epidermidis
C. Staphylococcus lugdunensis
D. Streptococcus sanguinis
E. Enterococcus faecalis

Answer

D. Streptococcus sanguinis

Detailed explanation

This patient has infective endocarditis.

The clues are:

• Fever and systemic symptoms
• New early diastolic murmur, suggesting aortic regurgitation
• Recent dental extraction
• Poor dentition
• Painless erythematous lesions on the palms, consistent with Janeway lesions
• Raised WBC and CRP

The most likely organism is Streptococcus sanguinis, a viridans streptococcus.

Viridans streptococci are normal oral flora and are strongly associated with infective endocarditis after dental procedures, especially in patients with poor dental hygiene or pre-existing valve abnormalities. Streptococcus sanguinis and Streptococcus mitis are classic examples.

The murmur described is important. An early diastolic murmur heard best at the left sternal edge in expiration suggests aortic regurgitation. In infective endocarditis, valve destruction can cause acute regurgitation. Aortic valve involvement can produce breathlessness due to acute volume overload.

Janeway lesions are painless erythematous or haemorrhagic lesions on the palms and soles. They are caused by septic emboli and are a classic peripheral sign of infective endocarditis.

Why the other options are wrong

A. Aggregatibacter actinomycetemcomitans
This is a HACEK organism and can cause infective endocarditis, especially culture-negative or slow-growing endocarditis. However, HACEK organisms are much less common than viridans streptococci in the setting of recent dental work and poor dentition.

B. Methicillin-sensitive Staphylococcus epidermidis
Staphylococcus epidermidis is a coagulase-negative staphylococcus. It is classically associated with prosthetic valve endocarditis, indwelling lines and implanted cardiac devices. This patient has no prosthetic valve or device.

C. Staphylococcus lugdunensis
Staphylococcus lugdunensis can cause aggressive native valve endocarditis and behaves more like Staphylococcus aureus than other coagulase-negative staphylococci. However, the dental extraction and poor oral hygiene point much more strongly toward viridans streptococci.

D. Streptococcus sanguinis
Correct. Streptococcus sanguinis is a viridans streptococcus found in the mouth and dental plaque. It is a classic cause of subacute infective endocarditis following dental procedures.

E. Enterococcus faecalis
Enterococcus faecalis can cause infective endocarditis, especially in older patients after genitourinary or gastrointestinal procedures. It is not the best fit here because the precipitating event is dental extraction.

Key exam point

Recent dental procedure + poor dentition + infective endocarditis = viridans streptococci, especially Streptococcus sanguinis or Streptococcus mitis.

Very important clinical trap

Staphylococcus aureus is now the most common overall cause of infective endocarditis, especially acute endocarditis and intravenous drug use. However, in an exam stem with poor dental hygiene or recent dental work, the best answer is usually viridans streptococci such as Streptococcus sanguinis.

Cheat sheet for exam

• Infective endocarditis = fever + murmur + embolic/immunological signs.
• Janeway lesions = painless lesions on palms/soles; septic emboli.
• Osler nodes = painful finger/toe pulp lesions; immune complex phenomenon.
• Roth spots = retinal haemorrhages with pale centres.
• Splinter haemorrhages = linear nail-bed haemorrhages.
• Dental procedure or poor dentition = viridans streptococci.
• Viridans streptococci include Streptococcus sanguinis and Streptococcus mitis.
• Staphylococcus aureus = most common overall cause, acute disease, IVDU, skin source.
• IVDU = often right-sided endocarditis, especially tricuspid valve; Staphylococcus aureus common.
• Prosthetic valve early after surgery = coagulase-negative staphylococci, especially Staphylococcus epidermidis.
• Streptococcus bovis/gallolyticus endocarditis = think colorectal cancer.
• Enterococcus faecalis = GU/GI source, older men, instrumentation.
• HACEK organisms = slow-growing Gram-negative organisms; culture-negative endocarditis.
• Culture-negative endocarditis also occurs after prior antibiotics.
• Coxiella burnetii = Q fever endocarditis.
• Bartonella = culture-negative endocarditis, homelessness/body lice or cat exposure.

Flash cards

Q: What organism is classically associated with infective endocarditis after dental extraction?
A: Viridans streptococci, especially Streptococcus sanguinis or Streptococcus mitis. They are oral flora found in dental plaque.

Q: What are Janeway lesions?
A: Painless erythematous or haemorrhagic lesions on the palms and soles due to septic emboli in infective endocarditis.

Q: What are Osler nodes?
A: Painful lesions on the fingers or toes caused by immune complex deposition in infective endocarditis.

Q: Which organism is most commonly associated with prosthetic valve endocarditis soon after surgery?
A: Staphylococcus epidermidis, a coagulase-negative staphylococcus.

Q: Which endocarditis organism should prompt consideration of colorectal malignancy?
A: Streptococcus bovis, especially Streptococcus gallolyticus.

Q: Which organism is now the most common overall cause of infective endocarditis?
A: Staphylococcus aureus.

Q: In an intravenous drug user with tricuspid valve endocarditis, what organism is most likely?
A: Staphylococcus aureus.

Q: What does an early diastolic murmur at the left sternal edge suggest?
A: Aortic regurgitation, which may occur due to aortic valve destruction in infective endocarditis.

MCQs

1. A 63-year-old man develops fever and a new murmur 3 weeks after dental scaling. He has poor oral hygiene. Blood cultures grow alpha-haemolytic Gram-positive cocci. What is the most likely organism?

A. Staphylococcus aureus
B. Streptococcus sanguinis
C. Candida albicans
D. Pseudomonas aeruginosa
E. Streptococcus pneumoniae

Answer: B. Streptococcus sanguinis

Explanation: Dental work and poor dentition strongly suggest viridans streptococci. Streptococcus sanguinis is a classic oral viridans streptococcus causing subacute infective endocarditis.

2. Which of the following is false regarding Janeway lesions?

A. They are usually painless
B. They occur on palms and soles
C. They are caused by septic emboli
D. They are classically tender lesions on the finger pulps
E. They may occur in infective endocarditis

Answer: D. They are classically tender lesions on the finger pulps

Explanation: Tender finger or toe pulp lesions are Osler nodes. Janeway lesions are painless lesions on the palms and soles caused by septic embolic phenomena.

3. A 72-year-old man is diagnosed with infective endocarditis due to Streptococcus gallolyticus. Which investigation is most important after stabilisation?

A. Bronchoscopy
B. Colonoscopy
C. Temporal artery biopsy
D. Cystoscopy
E. Skin biopsy

Answer: B. Colonoscopy

Explanation: Streptococcus gallolyticus, formerly grouped under Streptococcus bovis, is associated with colorectal cancer and advanced colonic neoplasia. Colonoscopy is required.

4. A man with a prosthetic aortic valve inserted 3 weeks ago develops fever and positive blood cultures. Which organism is particularly associated with early prosthetic valve endocarditis?

A. Streptococcus pyogenes
B. Staphylococcus epidermidis
C. Mycoplasma pneumoniae
D. Neisseria meningitidis
E. Clostridium difficile

Answer: B. Staphylococcus epidermidis

Explanation: Early prosthetic valve endocarditis is often due to perioperative contamination with skin flora, especially coagulase-negative staphylococci such as Staphylococcus epidermidis.

5. Which of the following pairings is most accurate?

A. Dental procedure – Enterococcus faecium
B. Intravenous drug use – Staphylococcus aureus
C. Colorectal cancer – Streptococcus pyogenes
D. Prosthetic valve early infection – Streptococcus pneumoniae
E. Culture-negative endocarditis – Escherichia coli

Answer: B. Intravenous drug use – Staphylococcus aureus

Explanation: Staphylococcus aureus is common in acute endocarditis and intravenous drug use, often affecting the tricuspid valve. Dental procedures suggest viridans streptococci; colorectal malignancy suggests Streptococcus gallolyticus; prosthetic valves suggest coagulase-negative staphylococci.

6. Which of the following is a HACEK organism?

A. Enterococcus faecalis
B. Klebsiella pneumoniae
C. Eikenella corrodens
D. Staphylococcus aureus
E. Streptococcus sanguinis

Answer: C. Eikenella corrodens

Explanation: HACEK organisms include Haemophilus species, Aggregatibacter, Cardiobacterium, Eikenella and Kingella. They are slow-growing Gram-negative organisms associated with culture-negative endocarditis.

7. Which of the following is false regarding viridans streptococci?

A. They are commonly found in the oral cavity
B. They include Streptococcus sanguinis
C. They may cause endocarditis after dental procedures
D. They are the typical cause of right-sided endocarditis in intravenous drug users
E. They may cause subacute infective endocarditis

Answer: D. They are the typical cause of right-sided endocarditis in intravenous drug users

Explanation: Right-sided endocarditis in intravenous drug users is classically due to Staphylococcus aureus. Viridans streptococci are more associated with oral sources and subacute native valve endocarditis.

8. A patient with suspected infective endocarditis has fever, a new regurgitant murmur and painless lesions on the palms. What is the most appropriate interpretation of the skin lesions?

A. Osler nodes due to immune complex deposition
B. Janeway lesions due to septic emboli
C. Erythema nodosum due to sarcoidosis
D. Gottron papules due to dermatomyositis
E. Palmar xanthomata due to dyslipidaemia

Answer: B. Janeway lesions due to septic emboli

Explanation: Painless palmar or plantar lesions in endocarditis are Janeway lesions. Osler nodes are painful and usually affect the finger or toe pulps.

9. A patient with fever and a new murmur has had two sets of negative blood cultures after receiving antibiotics from his GP. Which is the most likely reason for culture-negative endocarditis?

A. Prior antibiotic exposure
B. Hyperkalaemia
C. Atrial fibrillation
D. Iron deficiency anaemia
E. Hypertension

Answer: A. Prior antibiotic exposure

Explanation: The most common reason for culture-negative endocarditis is prior antibiotic treatment before blood cultures are taken. Other causes include Coxiella, Bartonella, Brucella and HACEK organisms.

10. Which clinical feature most strongly supports infective endocarditis in a febrile patient after dental extraction?

A. Wheeze with normal inflammatory markers
B. Isolated pleuritic chest pain
C. New early diastolic murmur
D. Microscopic haematuria from renal stones
E. Unilateral calf swelling

Answer: C. New early diastolic murmur

Explanation: Fever plus a new regurgitant murmur is highly suggestive of infective endocarditis. An early diastolic murmur suggests aortic regurgitation, which may result from aortic valve infection and destruction.

Summary for quick exam revision

Infective endocarditis should be suspected when fever is accompanied by a new murmur, embolic signs or peripheral stigmata. Recent dental extraction and poor dentition point strongly toward viridans streptococci because these organisms live in the mouth and dental plaque. Streptococcus sanguinis is a classic viridans streptococcus causing subacute native valve endocarditis after dental procedures. Staphylococcus aureus is now the most common overall cause of infective endocarditis, especially in acute presentations, intravenous drug users and skin-source infection. Intravenous drug use commonly causes right-sided, especially tricuspid, endocarditis due to Staphylococcus aureus. Early prosthetic valve endocarditis is classically caused by coagulase-negative staphylococci such as Staphylococcus epidermidis. Streptococcus gallolyticus, formerly associated with Streptococcus bovis, should trigger evaluation for colorectal cancer. Enterococcal endocarditis is associated with genitourinary or gastrointestinal sources, especially in older patients. HACEK organisms are slow-growing Gram-negative organisms and are recognised causes of culture-negative endocarditis. Prior antibiotic exposure is the commonest reason blood cultures may be negative in endocarditis. Janeway lesions are painless palm or sole lesions caused by septic emboli. Osler nodes are painful lesions on the fingers or toes due to immune complex deposition. Roth spots are retinal haemorrhages with pale centres. An early diastolic murmur at the left sternal edge suggests aortic regurgitation, which may occur when endocarditis damages the aortic valve. In exam stems, the best organism is chosen from the clinical context: dental source means viridans streptococci, IVDU means Staphylococcus aureus, prosthetic valve means Staphylococcus epidermidis, and colorectal cancer association means Streptococcus gallolyticus.