Comparison of O-Antigen Gene Clusters of All O-Serogroups of Escherichia coli and Proposal for Adopting a New Nomenclature for O-Typing

Abstract

Escherichia coli strains are classified based on O-antigens that are components of the lipopolysaccharide (LPS) in the cell envelope. O-antigens are important virulence factors, targets of both the innate and adaptive immune system, and play a role in host-pathogen interactions. Because they are highly immunogenic and display antigenic specificity unique for each strain, O-antigens are the biomarkers for designating O-types. Immunologically, 185 O-serogroups and 11 OX-groups exist for classification. Conventional serotyping for O-typing entails agglutination reactions between the O-antigen and antisera generated against each O-group. The procedure is labor intensive, not always accurate, and exhibits equivocal results. In this report, we present the sequences of 71 O-antigen gene clusters (O-AGC) and a comparison of all 196 O- and OX-groups. Many of the designated O-types, applied for classification over several decades, exhibited similar nucleotide sequences of the O-AGCs and cross-reacted serologically. Some O-AGCs carried insertion sequences and others had only a few nucleotide differences between them. Thus, based on these findings, it is proposed that several of the E. coli O-groups may be merged. Knowledge of the O-AGC sequences facilitates the development of molecular diagnostic platforms that are rapid, accurate, and reliable that can replace conventional serotyping. Additionally, with the scientific knowledge presented, new frontiers in the discovery of biomarkers, understanding the roles of O-antigens in the innate and adaptive immune system and pathogenesis, the development of glycoconjugate vaccines, and other investigations, can be explored.

The Role of Pseudomonas aeruginosa Lipopolysaccharide in Bacterial Pathogenesis and Physiology

“…The O antigen polymer is comprised of repeating sugar units that are highly variable in structure between and within species [11]. In E. coli alone there are more than 180 known unique O antigen structures [28]. This variability is the basis of the intraspecies classification system, known as O-serotyping, which categorizes strains based on the specific O antigen presented on the cell surface.…”

Development of a Surface Programmable Activation Receptor system (SPAR): A living cell biosensor for rapid pathogen detection

“…Intact bacterial lipopolysaccharides (LPS) are macromolecules made up of three structural components: Lipid A, polysaccharide chain, and O-antigen. Distinctive O-antigen structures have been used to classify serogroups to E. coli , S. enteritidis , and V. cholerae (27); thus, E. coli O111 LPS was used to generate this serotype-specific monoclonal antibody. The use of a cell wall preparation dramatically reduced the time and labor required for hybridoma screening and shortened the timeline for monoclonal antibody production.…”

Diversity and evolution of surface polysaccharide synthesis loci in Enterobacteriales

“…The cps locus was defined by the presence of flanking genes galF and gnd and/or ugd, and is associated with the synthesis of group 1 and 4 capsules 48 . A cps locus reference database was created by combining reference loci previously identified in Escherichia 45,69 and Shigella 43 (typically called O antigen loci), Salmonella 44 (O antigen loci), and Klebsiella 46 (K antigen loci), amounting to 348 reference locus sequences (duplicate loci containing identical sets of homologous genes were removed). Next, all 27,365 isolates were scanned for the presence of a cps locus using an approach similar to the one previously described 46 .…”