Molecular diagnosis of prosthetic valve endocarditis with aorto-right atrial fistula

Definite diagnosis of infective endocarditis is impossible when all blood cultures are negative under antibiotic treatment. In this case, Streptococcus canis was identified using polymerase chain reaction from preoperative whole blood and excised valve tissue, and considered as the pathogen for infective endocarditis, despite negative blood cultures. This information was useful for diagnosis and selection of antibiotics.