[Genetic characteristics and trends in the spread of a new Shigella flexneri subserovar with the antigenic formula IV:7,8].

As the result of experiments with the conjugation of S. flexneri strains 4 belonging to an unusual subserovar (IV: 7,8) with Escherichia coli donor strains K12 Hfr C and Hfr H, as well as experiments with converting phages IV and 7,8, this new subserovar of S. flexneri 4, similarly to other S. flexneri subserovars, was proved to be the Y-variant of shigellae rendered lysogenic by the two above phages. The experiments also revealed that 97.9% of all S. flexneri strains 4 (IV: 7,8) under study possessed invasive properties and were capable of inducing specific keratoconjunctivitis in guinea pigs. Observations on the isolation of S. flexneri strains 4 belonging to the new serovar (IV: 7,8), carried out by the All-Union Shigelloses Center on its basal territories in 1980-1984, made it possible to establish the tendency towards a wider circulation of this infective agent in the USSR.