Escherichia coli O75 antigen (O75)

The Escherichia coli O75 antigen is a specific O-polysaccharide component of the lipopolysaccharide (LPS) located on the outer membrane of certain Escherichia coli strains, particularly Extraintestinal Pathogenic E. coli (ExPEC) [1, 14]. It plays a vital role in bacterial virulence by contributing to the structural integrity of the cell envelope and protecting the bacterium from host immune mechanisms, such as serum-mediated lysis and phagocytosis [9, 14]. Serotype O75 is recognized as one of the most prevalent antigens associated with invasive E. coli disease (IED), including bacteremia and urosepsis, particularly in older adults and individuals with recurrent urinary tract infections [1, 5, 21]. Due to its clinical significance, the O75 antigen is a key target in the development of multivalent bioconjugate vaccines, such as ExPEC9V and ExPEC10V [2, 3, 5]. These vaccines are designed to stimulate the production of functional antibodies that facilitate the opsonophagocytic killing of the pathogen, thereby preventing severe systemic infections [2, 6]. The O75 antigen's structural diversity is a hallmark of E. coli serotyping and is critical for epidemiological tracking of pathogenic outbreaks [14]. Therapeutic strategies focusing on this antigen aim to provide broad protection against the diverse strains of ExPEC that utilize O75 for survival within the host [4, 8].

Other names

O75 polysaccharideE. coli O75 LPSO75 O-antigenECOO75Escherichia coli O75 O-antigen

Induction of antigen-specific functional antibodies (IgG) that promote opsonophagocytic killing (OPK) of the bacteria by host immune cells [2, 3, 9].