[Endocarditis with unusual causative agents].

In the period 1947-1985, 601 patients with infective endocarditis were seen at the University Hospital Zurich and the Kantonsspital Lucerne. Streptococci, enterococci and staphylococci were the predominant causative organisms in two-thirds of all cases. In more than 25% of the patients blood cultures remained negative. In 6 patients endocarditis was caused by very rare organisms, viz. Coxiella burnetii (2 cases), Hemophilus parainfluenzae, Corynebacterium bovis (diphtheroids), Brucella melitensis and Aspergillus terreus. The clinical and microbiological characteristics of these cases are described and compared with the results in the literature. Diagnostic and therapeutic problems are discussed. Only with special awareness of the role of these unusual organisms in causing infective endocarditis, especially Q fever endocarditis with its notoriously atypical course, can the number of "culture negative" cases be diminished and the prognosis thereby improved.