Classification and actual antigenic composition of Salmonellae.

: The synthesis by Enterobacteriaceae grown on artificial media of proteins, with a diversity of specificities previously found with the help of antiprotein sera, is confirmed with antibacterial sera prepared with species belonging to different serogroups. An earlier recognition of the existence of these materials was hindered by the devised schemes of classification and the claims relating 'O' factors to the bacterial polysaccharides. The synthesis, on artificial media, of mixtures of heterologous proteins by all the analysed species is no proof that their behaviour in vivo is identical; notwithstanding their high amounts in the mixtures, few of the heterologous proteins are involved in cross-protection of a host against its natural pathogen.