[Antigens of Shigella dysenteriae serovars 3-7. III. Chemical composition, toxic and physicochemical properties of exotoxins].

The exotoxins of Shigella dysenteriae, serovars 3-7, were isolated. These exotoxins were found to differ from O-antigens in their chemical composition and resistance to heating, drying and the action of chemical substances. The toxicity of exotoxin was determined by its thermolabile component. Exotoxin formation varied in different strains. The preparations obtained from the cultures in the S-form, isolated from patients with severe toxic forms of the infectious process, possessed the highest toxicity. The cultures (in the S- and R-forms), kept for a long time in culture media at the museum of the laboratory, completely lost their capacity for exotoxin synthesis.