[Proceedings: Microbiology of endocarditis].

The classical paper published by Schottmüller in 1903 has shown beyond doubt that blood cultures are a crucial diagnostic procedure for the diagnosis of endocarditis. Positive blood cultures also make it possible to distinguish between bacteremia and endocarditis: in the latter condition the number of organisms per ml of blood is relatively constant and all blood cultures are usually positive. Gram positive cocci are still the commonest organisms found in classical endocarditis. Gram negative organisms, yeasts and fungi are cultured with increasing frequency in cases of endocarditis secondary to valve replacement. Sensitivity testing by the disc diffusion method determines the minimal inhibitory concentration of the antibiotic towards the isolated organism. However, minimal bactericidal concentrations are of much greater prognostic value in endocarditis and should be performed routinely on the isolated organism.