[Characteristics of the action of the biologically active factor from virulent Shigella flexneri strains in a study on mice and a cell culture].

The authors subjected to further study the biologically active factor revealed by them earlier in the virulent Sh. flexneri cultures by using the genetically bound triad of Sh. flexneri 5a-222 cultures and the corresponding couple of Sh. flexneri 2a-516. There was shown correlation of the strains virulence determined by the keratoconjunctival test, with the presence of genetically-determined production of the biologically active factor detectable in the culture filtrate, which produced toxic action of the continuous cell cultures in the virulen Sh. flexneri strains of different serovars (2a and 5a), and lethal action in intravenous injection to mice. Comparative study of toxicity of the preparations of the endotoxin, free endotoxin, and neurotoxin types showed the biologically active factor to resemble the neurotoxin, differing from it in the toxic action and thermolability. Filtrates of the virulent and genetically characterised avirulent strains differed in the protein and lipids content, this permitting to suggest participation of the protein and lipid complex in the toxic action of the biologically active factor.