The role of the microbiology laboratory in the diagnosis and antimicrobial treatment of infective endocarditis.

The laboratory diagnosis of infective endocarditis is based on isolation of the etiologic agent from blood cultures. Major variables affecting the yield of microorganisms include the volume of blood cultured and the number of cultures performed, the atmosphere of incubation of cultures, and the frequency of examination and subculture of blood cultures. Bactericidal tests of antibiotics, singly and in combination, are important in determining the therapeutic regimen.