STUDIES ON EXPERIMENTAL BACTERIAL ENDOCARDITIS

Abstract

Cardiac hyperfunction is regarded as one of the causes inducing subacute bacterial endocarditis (S.B.E.). In the present study, Digitamin (digitalis preparation Shionogi) injection and forced movement were used as the tools to give over-load to the heart. Methods and results are summarized as follows:
1) Six rabbits were injected with Digitamin and Streptococcus sanguis, strain A, which was isolated from a patient, with S.B.E..
Bacterial endocarditis was found in none of these animals.
2) Six rabbits were similarly treated with Digitamin and Streptococcus sanguis, strain B, which was obtained by rabbit passages of strain A.
In 2 of 6 cases, bacterial endocarditis with certain pathological changes could be produced.
On the other hand, 3 rabbits which were inoculated only with strain B showed no finding of bacterial endocarditis. It is considered that in this experiment the combination of Digitamin and strain B has been necessary to cause bacterial endocarditis, and Digitamin has played an important rôle in causing the disease by its cardiotonic activity.
3) Eight rabbits were put in a round wire cage separately, which was quickly turned for the purpose of making the animals exhausted.
All animals were pathologically studied for changes in the heart after being sacrificed.
Two of 4 cases which were subsequently inoculated with strain B showed the signs of bacterial endocarditis (Fig. 4), while the other 4 rabbits which were not otherwise treated showed the following abnormalities.
1. Hypertrophy and exfoliation of the endothel cells of valves.
2. Platelet-thrombus on valves (Fig. 1, Fig. 2).
3. Development of fibrocytes and fibroblasts in endocardium.
4. Cell infiltration in endocardium (Fig. 3).
These minute changes are supposed to offer a clue to the onset of bacterial endocarditis by subsequent inoculation with bacteria.
From the above experiments, it was concluded that Digitamin injection and forced movement are important factors which cause bacterial endocarditis through giving overload to the heart, so far as they are combined with a certain virulent strain of Streptococcus sanguis.