A 25-year-old man was found dead at home by the apartment manager, who had been called by the decedent's employer because of failure to report to work for the past 3 days. An external examination by the medical examiner showed splinter hemorrhages under the fingernails and no signs of trauma. The gross appearance of the heart at autopsy is shown in the figure. Which of the following laboratory findings is most likely to provide evidence of the cause of the disease? (A) Elevated antis treptolys in O titer (B) Positive ANCA determination (C) Increased creatine kinas e-MB fraction (CK-MB) (D) High double-stranded DNA autoantibody titer (E) Positive blood culture for Staphylococcus aureus