Interrelationships between the virulence and the presence of M-protein in hemolytic streptococcus group A]

Experiments on mice demonstrated that of hemolytic streptococci A M types 2, 3, 12, 22, 46, and 49 characteristic is the absence of parallelism between their virulence for mice and the presence of M+-colonies in the microbial population. There was also a greater virulence for mice of M-variants. The established changes in serological properties of the cultures passaged in vitro were brought to the acquisition of polyagglutinability by the passage cultures, and to the loss of type-specific protection by the immune sera against these cultures. A possibility of acquisition by passage cultures of a factor determining their high virulence for mice, nonidentical to M-protein, is discussed.