Incidence and risk factors for endocarditis among patients with health care-associated Staphylococcus aureus bacteraemia

Background: Staphylococcus aureus infective endocarditis (IE) is a characteristic community-acquired infection, however most cases are presently occurring in the health care setting. This study investigated the incidence and risk factors for S. aureus IE in patients with nosocomial and health care-associated S. aureus bacteraemia (SAB). Methods: Consecutive patients with health care-associated and hospital-acquired SAB were prospectively recruited over a 30-month period. Patients were followed up for at least 12 weeks after the initial positive blood culture result. The primary endpoint was the diagnosis of IE. Results: IE occurred in 11 of 303 patients (3.6%). Patient characteristics at diagnosis and that were associated with IE included the number of positive blood cultures obtained during hospitalization (p =0.003), the duration of bacteraemia (p <0.001), bacteraemia persisting for >3 days (odds ratio (OR) 14.5, 95% confidence interval (CI) 4.0-52.8; p <0.001), performance of echocardiography (OR 1.88, 95% CI 1.69-2.1; p =0.001), presence of a well known predisposing risk for IE (OR 57.2, 95% CI 13.6-240.5; p <0.001), a non-fatal McCabe score (OR 2.10, 95% CI 1.4-3.1; p =0.02), and the duration of fever related to the infection (p =0.026). On multivariable analysis, the presence of a predisposing risk for IE, prolonged bacteraemia, and non-fatal McCabe score remained significantly associated with IE. Conclusions: In this study the incidence of IE was lower than previously reported. Three clinical characteristics were identified as risk factors for IE among patients with SAB acquired in a health care setting.