Valvular Heart Disease in Adults: Infective Endocarditis

A variety of microorganisms can cause infective endocarditis (IE) in patients with native valves. Staphylococci and streptococci are most common in community-acquired IE; staphylococci are most common in nosocomial IE. Microbiology of prosthetic valve endocarditis (PVE) depends on timing. Early-onset PVE (ie, 60 days or fewer postsurgery) typically is nosocomial, with Staphylococcus aureus infection being most common. Intermediate-onset PVE (ie, 60 to 365 days postsurgery) typically involves a mix of nosocomial and non-nosocomial organisms. PVE that develops more than 1 year after surgery has microbiology similar to that of native valve endocarditis. Fever is the most common symptom; others include dyspnea, pleuritic pain, anorexia, and myalgias. The Modified Duke Criteria is the standard for diagnosis, with blood cultures being the most important test. If patients are in stable condition, three sets of blood cultures should be obtained more than 6 hours apart and from separate sites before starting antibiotics. Echocardiography aids in diagnosis and can identify conditions best managed with surgery. For empiric therapy for native valve IE, most patients should receive vancomycin. For PVE, vancomycin and gentamicin should be prescribed, plus cefepime or an antipseudomonal carbapenem. Treatment typically continues for 6 weeks after blood culture results are negative.