[Separation of Shigella toxins into fractions differing in biological activity and characteristics of the fractions inducing penetration in avirulent strains].

The results obtained in the study of the biological activity of the lysates of 14 Sh. flexneri and Sh. sonnei strains differing in their virulence are presented. In the lysates of the virulent cultures 2 kinds of biological activity corresponding to the fractions of peaks I and II could be detected: one fraction possessed HeLa toxicity, the other fraction possessed enterotoxic activity. The avirulent nonpenetrating mutants had no HeLa toxicity, but retained their capacity for producing factors similar to enterotoxin. When added to a nontoxic dose, HeLa toxin produced by the virulent Shigella strains enhanced the penetration capacity of the virulent strains and imparted this capacity to the avirulent cultures of a homologous Shigella species.