Experimental bacterial endocarditis due to Streptococcus mitis.

It is important in order to advance the increasingly successful attack on subacute bacterial endocarditis to be able to produce the disease experimentally and to treat it with new and improved therapeutic regimens. Since endocarditis caused by Streptococcus mitis has not been consistently produced previously in the dog, a study was undertaken in which cardiovascular stress was created by the establishment of aortico-inferior vena caval and bilateral iliofemoral arteriovenous shunts. After a period of antibacterial treatment and of stabilization, daily intravenous injections of broth cultures of S. mitis were begun. In 50 per cent of 24 animals bacterial endocarditis developed, simulating that found in clinical cases at necropsy. These animals had widely patent fistulas and 11 showed evidences of congestive heart failure. Of the remaining 12 animals, five with patent fistulas died of the effects of multiple infected pulmonary emboli. Seven others whose shunts had closed were killed and found to have no significant lesions other than healed caval infections.