BIVALENT LIVING VACCINES AGAINST BACTERIAL INTESTINAL PATHOGENIC AGENTS, PROCESS FOR PREPARING THE SAME, PLASMIDS AND STRAINS USEFUL AS BASE MATERIAL

摘要

A bivalent S. typhi living vaccine is disclosed. The micro-organism contained in this vaccine is capable of expressing a complete LPS with a S.-typhi core and heterologous O-polysaccharides. The micro-organism can be produced by transferring the rfa-L gene from E. coli and the gene region of a cross-reacting species whose genetic products catalyze the biosynthesis of O-lipopolysaccharides, into S. typhi.