Abstract:

SEVERAL studies were undertaken in order to reproduce in laboratory animals cardiac lesions which would resemble those appearing in human beings suffering from the sequelae of streptococcal infections (Schultz, 1936 ; Smith, Morgan and Mudd, 1940; Gross, Cooper and Philips, 1941; Robinson, 1947; Schultz, 1947; Murphy and Swift, 1949; Murphy, 1949; Clawson, 1950; Robinson, 1951; Murphy, 1952; Glaser, Thomas, Morse and Darnell, 1956). These studies describe the histopathological changes obtained in laboratory animals following inoculation by various routes of haemolytic streptococci, of their products and of a number of other micro-organisms. As to the mechanism involved in the production of cardiac lesions, two main theories have been proposed: (a)allergic phenomena,or production ofa uto- antibodies to the heart muscle (Rich and Gregory,1944; Rich,1946; Cavelty, 1947a and 1947b), (b) direct action of haemolytic streptococci and their toxins on the heart muscle (McLeod, 1953; Kellner and Robertson, 1954a and 1954b). Although both theories have been supported by some experimental evidence, the exact mechanism has not yet been clarified. This study describes the histo-pathological changes obtained in rabbits as a result of single intramyocardial injections of haemolytic streptococci and their cell-free extract, as well as of other bacterial species, both related and not related to haemolytic streptococci. The possible mechanism involved, and especially the role of trauma to the myocardium, in inducing cardiac lesions, is described.