S. aureus is the most common pathogen responsible for prosthetic valve endocarditis but still accounts for only 23% of cases. The leading cause of culture-negative IE is the use of antibi- otics before blood cultures are obtained. Negative blood cultures in the setting of IE delay diagnosis and often require additional serological and poly- merase chain reaction testing.22,35,36 Recommendations for Intervention for IE Referenced studies that support the recommendations are summarized in Online Data Supplement 42. 