Klebsiella pneumoniae O-antigen (O-antigen (occasionally "OPS" for O-antigen polysaccharide, but no universal abbreviation specific to K. pneumoniae))

The Klebsiella pneumoniae O-antigen is a polysaccharide comprised of repeating carbohydrate monomers attached to the core oligosaccharide of bacterial lipopolysaccharide (LPS)[1][2][6]. The molecular structure defines nine principal serotypes (O1, O2a, O2ac, O3, etc.), each with unique carbohydrate repeat units, which are biosynthesized by enzymes encoded in the *rfb* gene cluster[2][6][5]. O-antigen expression provides resistance against complement-mediated killing, facilitates immune evasion, and is a key virulence determinant[1][4]. The O-antigen serves as a validated molecular target for experimental immunotherapeutics, and ongoing studies focus on developing monoclonal antibodies and vaccine candidates directed against dominant serotypes[2][6]. Antigenic diversity among isolates poses challenges for broad-spectrum targeting, but O-antigen-based genotyping is vital for clinical epidemiology and guiding precision therapies[5][2]. If more specific information is needed (e.g., for a particular O-antigen serotype like O1 or O2a), further specification will improve the structured output[6][5][8].

Other names

O-polysaccharideOPSO-specific polysaccharideLPS O-antigenLipopolysaccharide O-antigen

Antibody-mediated neutralization (anti-O-antigen antibodies disrupt bacterial survival by promoting opsonization and complement activation); Inhibition of immune evasion (antibody binding overcomes O-antigen’s protective role against complement-mediated lysis).