[A 41 year-old male patient with fever of unknown origin and bacteremia with actinobacillus actinomycetemcomitans].

A 41-year-old male patient presented with fever of unknown origin which had been present for 5 months. The primary diagnostic procedures did not identify an infectious focus. After a lag phase of 13 days, blood cultures became positive for Actinobacillus actinomycetemcomitans, which belongs to the HACEK group of microorganisms. According to the DUKE criteria, infective endocarditis was diagnosed despite negative transesophageal echocardiography (TEE). The sensitivity of TEE is estimated between 86 and 94%. An infected tooth was extracted as a possible focus, and the patient was treated with i.v. antibiotics for 5 weeks according to the guidelines of the AHA and ACC. The fever was permanently terminated, and the further course of the patient was uneventful. Despite negative TEE, the diagnosis "infective endocarditis" should not be rejected, and blood cultures should be grown for up to 30 days.