Abstract
Aortic valve endocarditis with extension to the tricuspid annulus and ventricular septum in an intravenous drug abuser - with Mycobacterium avium-intracellulare identified as the offending organism - forms the basis of this report. The aortic root and ventricular septal defect were successfully repaired using an aortic cryopreserved homograft. This case is of particular interest because M avium-intracellulare has not been recognized as a cause of endocarditis. The incidence of atypical organisms as a cause of endocarditis may increase in the future because of the rise of drug abuse and the acquired immune deficiency syndrome in North America.