Which of the following is the most common cause of native valve infective endocarditis in the community?
ExplanationThe etiologic agents of infective endocarditis vary by host (see Figure IV-13). Community-acquired native valve endocarditis remains an important clinical problem, particularly in elderly people. In those patients, streptococci (Viridans spp., S. gallolyticus, other non–group A and other group streptococci, and Abiotrophia spp.) account for approximately 40% of cases. Staphylococcus aureus (30%) is next most common. Enterococci, HACEK group, coagulase-negative, and culture-negative cases each account for less than 10% of community-acquired native valve cases. In health care–associated, injection drug use–associated, and greater than 12-month-old prosthetic valve endocarditis, S. aureus is most common. Coagulasenegative staphylococcus is the most common organism in prosthetic valve endocarditis less than 12 months. Enterococci cause endocarditis in approximately 10% to 15% of cases in health care–associated, 2- to 12-month prosthetic valve, and injection drug use cases. Culture-negative endocarditis accounts for 5% to 10% of cases in all of the aforementioned clinical scenarios.
