Abstract
When the aortic or mitral valves of dogs are injured by passing a suitable steel rod down the left carotid artery, the resulting wound of the valve shows, at the end of 49 days, a hyalin-like mass at the point of injury. As late as 60 days after such injury the injection intravenously, of non-hemolytic streptococci results, constantly, in a bacterial vegetative growth on the injured area productive of petechiae, infarctions, thrombo-glomerular nephritis, and small areas in the heart muscle in which a round cell infiltration follows a punctate hemorrhage.
In four dogs the healing of the injury was not altered by the injection either before or after injury, of egg albumin, followed in three weeks by a second injection, which was in turn made three days before autopsy.
A strain of non-hemolytic streptococcus isolated from the blood of a patient with acute rheumatic fever, and having some virulence for white mice, and a strain from a normal throat having no virulence for mice, were equally successful in producing the infection of the injured valve.
Subacute bacterial endocarditis in humans is characterized by the presence in the blood stream of avirulent non-hemolytic streptococci. These streptococci are said to be avirulent from the standpoint of the action on white mice. They may or may not have been virulent before infecting the human subject.
Cultures of the strain from acute rheumatic fever, recovered from dogs with endocarditis produced as above, failed to infect fresh animals in two instances. A culture of the strain from a normal throat after such passage through a dog failed to infect a fresh animal which had had a valvular injury. Furthermore two different strains from clinical cases failed to infect animals whose valves had previously been injured.
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