Observations on the serologic changes in the recombinants in Shigella flexneri Serotype 4a

Studies on the antigenic composition of 84 diagnostic strains of S. flexneri serotype 4a and their Lac+ recombinants from a cross with E. coli HfrC were carried out. Considerable differentiation of agglutination reaction was found both in original material and in recombinants. An interesting group included recombinants which completely lost their capability to agglutinate with sera specific for type and group antigens and preserved only the capability to agglutinate in the polyvalent serum of S. flexneri subgroup. One of them (recombinant 140 Lac+) had been subject to detailed serological analysis and was shown to acquire as a result of recombination a new antigen appearing neither in any flexneri subgroup serotype, nor in dysenteriae and boydii subgroups. This antigen is of thermostable character.