Patent ID: 8133493

Claim:
A live attenuated strain of Salmonella comprising (a) a regulatable araCP BAD promotor that is operably linked to a fur gene, wherein said fur gene is expressed when said attenuated strain is in the intestinal tract of an individual and said fur gene is not expressed when said attenuated strain is within internal tissues of an individual and wherein non- expression of said fur gene in vivo causes synthesis of iron regulated outer membrane proteins (IROMPs); and (b) a means for regulating synthesis of an LPS O-antigen, wherein said LPS O-antigen ceases to be synthesized in vivo, exposing an LPS core oligosaccharide antigen that is conserved among Salmonella species; wherein said attenuated strain is a Salmonella typhimurium strain and has enhanced ability to induce immune responses against Salmonella typhimurium and Salmonella enteritidis species.