bacterial endocarditis

Bacterial endocarditis occurs when bacteria adhere to and proliferate on heart valves or endocardial surfaces, forming vegetations composed of fibrin, platelets, and microorganisms. Acute endocarditis typically involves normal valves infected by highly virulent organisms like Staphylococcus aureus, presenting rapidly with high fever and systemic toxicity. Subacute endocarditis usually affects abnormal valves (congenital defects, rheumatic disease, prosthetic valves) with less virulent organisms like viridans group streptococci, presenting insidiously over weeks to months. Pathophysiology involves initial endothelial damage, platelet-fibrin deposition, and bacterial adherence facilitated by surface proteins. Clinical manifestations include fever (90% of cases), new or changing heart murmurs, and classic findings like Janeway lesions, Osler nodes, splinter hemorrhages, and Roth spots. Major complications include valve destruction leading to heart failure, systemic embolization causing stroke or organ infarction, and metastatic infections forming abscesses. Diagnosis relies on modified Duke criteria combining clinical, microbiological (positive blood cultures), and echocardiographic evidence (vegetations, valve dysfunction). Treatment requires prolonged IV antibiotics (4-6 weeks) with bactericidal agents, and surgical intervention may be necessary for severe valve dysfunction, large vegetations, or treatment failure.