U01.07.050 Bacterial endocarditis

Bacterial endocarditis is an infection of the endocardial surface of the heart, typically involving the heart valves. It can be acute or subacute, depending on the causative organism and clinical course.

Types of Bacterial Endocarditis

Type	Causative Organism	Characteristics
Acute	Staphylococcus aureus (high virulence)	Large vegetations on previously normal valves, rapid onset.
Subacute	Viridans streptococci (low virulence)	Smaller vegetations on congenitally abnormal or diseased valves, gradual onset, often follows dental procedures.

Clinical Features

Symptoms and Signs

Fever (most common symptom)
New or changing heart murmur
Roth spots – Round white spots on the retina with surrounding hemorrhage
Osler nodes – Painful, raised lesions on fingers and toe pads (immune complex deposition)
Janeway lesions – Painless, erythematous macules on palms and soles
Splinter hemorrhages – Linear hemorrhages under the nail bed
Glomerulonephritis – Due to immune complex deposition
Septic arterial or pulmonary emboli

Mnemonic: FROM JANE ♥

Helps recall key features of bacterial endocarditis:

F – Fever
R – Roth spots
O – Osler nodes
M – Murmur
J – Janeway lesions
A – Anemia
N – Nail-bed hemorrhages
E – Emboli

Diagnostic Approach

Blood cultures – Multiple cultures are needed for accurate diagnosis.
Culture-negative endocarditis – Commonly caused by Coxiella burnetii, Bartonella species.
Echocardiography – Used to visualize vegetation on heart valves.

Valve Involvement and Special Associations

Valve Involved	Associations
Mitral valve (most common)	Native valve endocarditis
Tricuspid valve	IV drug use (S. aureus, Pseudomonas, Candida)
Aortic valve	Associated with high-virulence organisms
Prosthetic valves	S. epidermidis

Special Pathogens and Associations

Streptococcus bovis (now S. gallolyticus) → associated with colon cancer.
HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) → Cause culture-negative endocarditis.

Nonbacterial Endocarditis

Marantic (thrombotic) endocarditis – Due to malignancy or a hypercoagulable state.
Libman-Sacks endocarditis – Seen in systemic lupus erythematosus (SLE).

Key Points for USMLE Step 1

Recognize acute vs. subacute endocarditis and its causative organisms.
Memorize FROM JANE mnemonic for clinical features.
Know the role of blood cultures and culture-negative organisms.
Understand valve involvement and special associations (IV drug use, prosthetic valves, colon cancer).

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