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

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

Phylogenetic tree for all O-AGCs of <i>E</i>. <i>coli</i>.

<p>The O-AGCs that show 98–99.9% relatedness are highlighted.</p

O153 <i>wzx</i> and <i>wzy</i> genes amplified by PCR using primers from sequences presented in this investigation.

<p>Lanes 1, 7, 13: Molecular weight markers. Lane 2: Positive control for O153 targeting <i>wzx</i> gene, Lane 3: Negative control, Lanes 4,5,6: <i>wzx</i> amplified for three clinical isolates. Lane 9: Positive control for O153 targeting <i>wzy</i> gene. Lane 10: Negative control, Lane 11,12,13: <i>wzy</i> amplified for three clinical isolates.</p

Correction: Comparison of O-Antigen Gene Clusters of All O-Serogroups of <i>Escherichia coli</i> and Proposal for Adopting a New Nomenclature for O-Typing

Correction: Comparison of O-Antigen Gene Clusters of All O-Serogroups of <i>Escherichia coli</i> and Proposal for Adopting a New Nomenclature for O-Typin

O-groups that may be potentially merged based on similarities in O-AGC nucleotide sequence and serological cross-reactions.

<p>O-groups that may be potentially merged based on similarities in O-AGC nucleotide sequence and serological cross-reactions.</p

Comparison of O-AGC of O-groups that are 98–99.9% identical.

<p>Comparison of O-AGC of O-groups that are 98–99.9% identical.</p