A 50-year-old man presented to his family doctor complaining of flu-like symptoms. The doctor gave him a shot of penicillin and sent him home. The man came back a week later and in fact, felt worse. The man was a rancher and raised a lot of cattle. He told the doctor that he had congenital heart disease and an attack of rheumatic fever when he was young. The man now complained of fever, night sweats, continual coughing, weight loss, and lethargy. The doctor had the man hospitalized because he now suspected subacute bacterial endocarditis (SBE). A culture of his blood did not show any bacterial growth, but a serum analysis for antibodies against a certain bacterium was positive. As a result of finding antibodies to this organism, treatment with doxycycline was begun and the patient improved and was released from the hospital. What was the name of the organism with which the man was infected?