Infectious Disease · Cardiovascular Infections
The facts most likely to be tested
Staphylococcus aureus is the most common cause of acute infective endocarditis, particularly in patients with intravenous drug use or prosthetic valves.
Viridans group streptococci are the most common cause of subacute infective endocarditis following dental procedures or poor oral hygiene.
Streptococcus gallolyticus (formerly *S. bovis*) bacteremia or endocarditis is highly associated with underlying colorectal cancer or polyps.
Duke Criteria for diagnosis require either two major criteria, one major and three minor, or five minor criteria.
Major criteria include persistent positive blood cultures for typical organisms and echocardiographic evidence of endocardial involvement such as vegetations, abscesses, or new valvular regurgitation.
Peripheral stigmata of endocarditis include Osler nodes (painful, distal), Janeway lesions (painless, palms/soles), Roth spots (retinal hemorrhages), and splinter hemorrhages.
Enterococcus species are a common cause of endocarditis in elderly men following genitourinary procedures or instrumentation.
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A 58-year-old male presents with a two-week history of low-grade fevers, night sweats, and fatigue. He has a history of a mitral valve prolapse. Physical examination reveals a new holosystolic murmur at the apex, painless erythematous macules on his palms, and splinter hemorrhages under his fingernails. Blood cultures are pending. He recently underwent a colonoscopy that revealed a large villous adenoma.
Which organism is the most likely causative agent?
Streptococcus gallolyticus
The patient's presentation of subacute endocarditis combined with the history of a colonic villous adenoma is a classic board association for S. gallolyticus, testing the link between this organism and underlying gastrointestinal malignancy.
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Etiology / Epidemiology
Primary risk factors include prosthetic heart valves, IV drug use, and congenital heart disease. *Staphylococcus aureus* is the most common pathogen overall.
Clinical Manifestations
Classic presentation includes new-onset heart murmur, fever, and Osler nodes, Janeway lesions, and Roth spots. Splinter hemorrhages are common.
Diagnosis
Gold standard is Transesophageal Echocardiogram (TEE). Diagnosis requires meeting Duke Criteria (2 major, 1 major + 3 minor, or 5 minor).
Treatment
Empiric therapy is Vancomycin plus Ceftriaxone. Avoid aminoglycosides in patients with renal failure.
Prognosis
High mortality if untreated. Heart failure is the most common cause of death. Embolic events occur in 30-50% of cases.
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Epidemiology & Etiology
Patients with prosthetic valves or prior endocarditis are at highest risk. *Staphylococcus aureus* dominates in IV drug users (often tricuspid valve). *Streptococcus viridans* is the most common cause of subacute cases following dental procedures.
Pertinent Anatomy
The mitral valve is the most commonly affected valve in non-IVDU patients. The tricuspid valve is the classic site of infection in IV drug users due to venous return patterns.
Pathophysiology
Endothelial damage creates a site for platelet-fibrin thrombus formation (non-bacterial thrombotic endocarditis). Transient bacteremia leads to colonization of these vegetations. The resulting vegetation protects bacteria from host immune defenses, leading to persistent infection.
Clinical Manifestations
Patients present with persistent fever and a new or changing murmur. Look for Osler nodes (painful, distal pads) and Janeway lesions (painless, palms/soles). Acute heart failure is a surgical emergency requiring immediate valve replacement.
Diagnosis
The Duke Criteria is the diagnostic standard. Blood cultures must be drawn from three different sites before starting antibiotics. Transesophageal Echocardiogram (TEE) is the gold standard for visualizing vegetations >2mm.
Treatment
Empiric coverage targets staphylococci, streptococci, and enterococci using Vancomycin and Ceftriaxone. Gentamicin is often added for synergy but carries a high risk of nephrotoxicity and ototoxicity. Surgical intervention is indicated for refractory heart failure, persistent infection, or large mobile vegetations.
Prognosis
Complications include septic emboli to the brain, spleen, or kidneys. Heart failure remains the leading cause of mortality. Patients require serial echocardiograms to monitor vegetation size and valve function.
Differential Diagnosis
Rheumatic Fever: associated with migratory polyarthritis and Jones criteria
Non-bacterial thrombotic endocarditis: associated with hypercoagulable states like Trousseau syndrome
Atrial Myxoma: mimics constitutional symptoms but lacks positive blood cultures
Systemic Lupus Erythematosus: Libman-Sacks endocarditis involves sterile vegetations on both sides of the valve
Acute Pericarditis: presents with pleuritic chest pain relieved by leaning forward