Methicillin resistance and risk factors for embolism in Staphylococcus aureus infective endocarditis

Objective. Infective endocarditis caused by Staphylococcus aureus is an ominous prognosis associated with a high prevalence of embolic episodes and neurological involvement. Whether methicillin resistance decreases the risk of embolism in infective endocarditis is unclear. We sought to assess the association between methicillin resistance and risk factors for embolism in S. aureus infective endocarditis. Design. Retrospective chart review. Data from patients with infective endocarditis due to methicillin-resistant S. aureus were compared with data from patients with endocarditis due to methicillin-susceptible S. aureus. Logistic regression was used to identify independent risk factors for embolism. Setting. A 2,000-bed, university-affiliated tertiary care hospital. Patients. Between 1995 and 2005, 123 patients with S. aureus infective endocarditis were included in the study. There were 74 male patients and 49 female patients, with a median age of 54 years (range, 0-89 years). Results. Of 123 infections, 30 (24%) were nosocomial infections, and 14 (11%) were prosthetic valve infections. Of 123 S. aureus isolates, 48 (39%) were methicillin resistant. In total, embolism occurred in 45 (37%) of these patients: pulmonary embolism in 22 (18%), cerebral embolism in 21 (17%), and peripheral embolism in 6 (5%). The independent risk factors for an embolism were injection drug use, presence of a cardiac vegetation with a size of 10 mm or greater, and absence of nosocomial infection. For 83 patients with aortic or mitral infective endocarditis, independent risk factors for an embolism were the presence of a cardiac vegetation with a size of 10 mm or greater and endocarditis due to methicillin-susceptible S. aureus. Overall, in-hospital death occurred for 32 (26%) of 123 patients. Methicillin-resistant infection was not an independent risk factor for death. Conclusions. Methicillin-resistant S. aureus infection was associated with decreased risk of embolism in left-side endocarditis, but was not associated with in-hospital death.