Salmonella Enteritidis O:9 O-antigen polysaccharide (SE O-Ag)

The Salmonella Enteritidis O:9 O-antigen polysaccharide is a complex carbohydrate structure located on the outermost surface of the bacterium as part of its lipopolysaccharide (LPS) layer (PMID: 25650105). It consists of a repeating oligosaccharide backbone composed of mannose, rhamnose, and galactose, with a characteristic tyvelose side chain that defines the O:9 serogroup specificity within the Kauffman-White classification (PMID: 29158475). This molecule plays a vital role in bacterial virulence by protecting the pathogen from host immune mechanisms, such as the complement system and antimicrobial peptides, and by aiding in environmental survival (PMID: 23871461). In the context of human disease, Salmonella Enteritidis is a leading cause of foodborne gastroenteritis and can lead to severe invasive non-typhoidal Salmonella (iNTS) disease, particularly in sub-Saharan Africa. As a primary surface-exposed antigen, it is a major target for the development of glycoconjugate vaccines, such as CVD 1000 and GSK3888550A, which aim to elicit high titers of protective, bactericidal antibodies (PMID: 28919143, PMID: 30305333). Beyond vaccines, the O:9 antigen is also utilized in diagnostic serotyping and as a target for experimental monoclonal antibody therapies designed to neutralize the pathogen.

Other names

Salmonella Enteritidis O-polysaccharideSalmonella Group D O-antigenO9 antigenSalmonella Enteritidis lipopolysaccharide O-side chainTyvelose-containing O-antigen

Induction of serotype-specific bactericidal antibodies that facilitate opsonophagocytosis and complement-mediated killing of the bacteria (PMID: 28919143).