Abstract: This invention relates to mutant strains of gram-negative bacteria that constitutively secrete proteins via the type III secretion machinery and to methods of identifying molecules that are able to activate or inhibit secretion in wild-type strains of gram-negative bacteria by exposing gram-negative bacterial cells to a sample molecule, wherein the bacterial cells contain a reporter gene transcriptionally fused to a promoter of a gene activated or regulated by the type III secretion machinery and detecting the presence or activity of the product of the reporter gene.

Abstract: A purified immunogenic polypeptide comprises an epitope unit recognized by a protective monoclonal antibody having a high affinity and a high specificity for a surface polysaccharide of a pathogenic microorganism of bacterial, viral, or fungal origin. The polypeptide is capable of inducing an immune response in vivo against the pathogenic microorganism. The immune response confers protection in mice against challenge with the virulent microorganisms.

Abstract: A purified immunogenic polypeptide comprises an epitope unit recognized by a protective monoclonal antibody having a high affinity and a high specificity for a surface polysaccharide of a pathogenic microorganism of bacterial, viral, or fungal origin. The polypeptide is capable of inducing an immune response in vivo against the pathogenic microorganism. The immune response confers protection in mice against challenge with the virulent microorganisms.

Abstract: A method for modifying a wild strain of an entero-invasive Shigella to produce a modified strain of Shigella that can be used for making a vaccine against the wild strain of Shigella. The genome of the wild strain of Shigella is transformed so that it cannot substantially invade cells of a human host and cannot spread substantially within infected cells and from infected to uninfected cells of the host and cannot produce toxins which will kill substantial numbers of the host's infected, as well as uninfected, cells. A first gene of the wild strain of Shigella, coding for a protein necessary for the Shigella to invade cells of the host, and a second gene, coding for a protein necessary for the Shigella to spread within infected cells and between the infected and uninfected cells of the host, are mutagenized.

Abstract: The invention concerns a probe for the detection of shigellae and entero-invasive E. coli, containing a nucleic acid sequence originating from the 140 Mdal virulence plasmid of the M 90 T strain of Shigella flexneri; having a maximum size of around 27 kb and including all or part of the 27 kb Bam HI fragment.This probe permits the in vitro diagnosis of syndromes of dysentery or diarrhea, of the Shigellosis type.

Abstract: The invention concerns a probe for the detection of shigellae and entero-invasive E. coli, containing a nucleic acid sequence originating from the 140 Mdal virulence plasmid of the M 90 T strain of Shigella flexneri; having a maximum size of around 27 kb and inlcuding all or part of the 27 kb Bam HI fragment.This probe permits the in vitro diagnosis of syndromes of dysentery or diarrhea, of the Shigellosis type.