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).