1. A 30-year-old veterinarian on a cattle ranch presents with a 1-to-2-month history of malaise, chills, drenching malodorous sweats, fatigue, and weakness. He has anorexia and has lost 15 pounds. He has intermittent fevers that range up to 103 F (39.4 C). He complains of visual blurring. A physical examination reveals mild lymphadenopathy, petechiae, and a cardiac murmur consistent with aortic insufficiency. What is the most likely etiologic agent?