In the past several decades, S. aureus has become the primary pathogen responsible for infective endocarditis (IE). Improved dental care, hygiene, and the growing incidence of nosocomial infections and intravascular devices are associated with this bacteriologic shift. Among children with staphylococcal bacteremia, as many as 20% develop endocarditis, including patients with no predisposing cardiac valvular disease. Given this high complication rate, any patient with staphylococcal bacteremia should be followed closely for the development of a new murmur or other signs of endocarditis. Those patients with a new or changed murmur should undergo echocardiography. Persistent fever despite appropriate antibiotic therapy should also prompt the search for cardiac involvement even when patients have other foci of infection (such as skin) or the absence of clear signs of IE.

Definitive diagnosis of IE is made by pathologic or clinical criteria. Pathologic diagnosis requires positive histology or microbiology of tissue obtained at autopsy or cardiac surgery (valve tissue, vegetations, embolic fragments, or intracardiac abscess content). Without pathologic material, definitive clinical diagnosis can be difficult. Several sets of diagnostic criteria to evaluate patients for endocarditis have been developed. Studies have verified that the most recent criteria, the Duke criteria, are superior to older criteria for diagnosing infective endocarditis in children. The criteria are based on the microbiology of endocarditis and evidence of endocardial involvement by exam or echocardiography.

Major criteria include: