The numerous common antigens of enterobacteriaceae.

A mosaic of proteins is synthesized by each of the Enterobacterial species grown on artificial media (tryptose-agar, Difco). Their existence was proven with the help of sera prepared in rabbits with proteins from: S. enteritidis, S. typhi, S. typhimurium, S. paratyphi C, E. coli, and Sh. sonnei. The induced antibodies, strongly precipitated numerous heterologous Enterobacterial proteins. The proteins of Sh. dysenteriae 4, although reacting against the heterologous sera, were poor immunogens and induced, mainly, homologous antibodies. Comparative agar-gel diffusions of the same proteins against the antiproteinic sera and corresponding antibacterial sera proved that the bacteria induced fewer antibodies against a reduced number of heterologous antigens. Thus, it is evident that a competition among the numerous antigens of a bacterium takes place when whole bacteria are used for immunizations. The differences in the degree of relatedness of Salmonellae, Shigellae, and E. coli are illustrated by their reactions in agar-gel against homologous and heterologous sera. The serological activity of heated proteins (1 hr at 100 degrees C) against the antiproteinic sera differed according to the intrinsic qualities of the analysed materials.