Lipopolysaccharide O25b antigen (O25b)

The Lipopolysaccharide O25b antigen is a specific O-antigen serotype of the lipopolysaccharide (LPS) molecule found on the outer membrane of Gram-negative Escherichia coli, particularly the pandemic, multi-drug resistant ST131 lineage [1]. This antigen consists of repeating oligosaccharide units that extend from the bacterial surface, serving as a key virulence factor by protecting the bacterium from complement-mediated lysis and opsonophagocytosis [2]. Because the O25b serotype is highly correlated with the fluoroquinolone-resistant and extended-spectrum beta-lactamase (ESBL)-producing ST131 clone, it has become a high-priority target for precision antimicrobial strategies [3]. Therapeutic approaches include monoclonal antibodies, such as ASN-4, which facilitate immune-mediated clearance of the pathogen, and glycoconjugate vaccines like VLA1601 designed to elicit protective antibody responses [4]. Targeting this specific antigen offers a way to treat severe infections, including bacteremia and urinary tract infections, while minimizing collateral damage to the host's commensal microbiota [5].

Other names

O25b O-antigenEscherichia coli O25b antigenO25b-ST131 antigenLipopolysaccharide O25b

Opsonophagocytic killing (OPK) and complement-mediated bactericidal activity