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Chobi DebRoy

1:50-2:10 p.m., Monday
, PhD
Clinical Professor & Director, E. coli Reference Center
Department of Veterinary and Biomedical Sciences
Penn State
University Park, PA 16802 USA

Comparison of O-antigen gene clusters of all O-serogroups of Escherichia coli and suggestion for adoption of new nomenclature for O-serogenotyping

Chitrita DebRoy1, Pina M Fratamico2, Yan Xianghe2, GianMarco Baranzoni2, Yanhong Liu2, David Needleman2, Robert Tebbs3, Catherine D O'Connell3, Adam Allred3, Michelle Swimley3, Juan A Raygoza1, Michael Mwangi1, Robab Katani1, Elisabeth Roberts1

O-antigens are components of the lipopolysaccharide (LPS) in the cell envelope of Escherichia coli that are important virulence factors, targets of both the innate and adaptive immune system, and play a role in host-pathogen interaction.  O-antigens are highly immunogenic and display antigenic specificity unique for each strain, which are designated as O-serogroups.  There are 188 O-serogroups classified in E. coli, to date and there are other, OX groups, not so well recognized.   Conventional serotyping based on agglutination reactions between the O-antigen and antisera generated against each O-group, is the method commonly used for serogroups determination.  The procedure is labor intensive, not always accurate, and exhibits equivocal results.  Our objective was to develop methods for molecular serotyping or serogenotyping for O antigen determination.  In this report, we present the sequences of the O-antigen gene clusters (O-AGC) of 76 O-groups, including the OX groups (n=11) and a comparison of the O-AGC of all 199 O-groups.   Many of the O-groups that were designated with O type, on the basis of antigenic reactions, exhibit similar nucleotide sequences and also cross react serologically.   Some other O-AGCs carry insertion sequences or a few nucleotide differences.  Therefore, many of the O-groups should likely be eliminated and some can be merged.  We propose a revised O-group nomenclature based on nucleotide sequences of the O-AGCs of E. coli that will allow development of diagnostic platforms based on the genotypes of the O-AGCs that will be rapid, accurate and reliable for distinguishing the O-serogroups.   With the scientific knowledge presented, new frontiers on understanding the roles of O-antigens in the innate and adaptive immune system and pathogenesis, and the development of glycoconjugate vaccines, among others, can be explored. 

1E. coli Reference Center, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA.

2 Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA.

3 Animal Health & Food Safety, Life Sciences Solutions, Thermo Fisher Scientific, 2130 Woodward Street, Austin, TX.