MOLECULAR CHARACTERIZATION OF PATHOGENS AND THEIR RESPONSES TO ENVIRONMENTAL FACTORS
Location: Molecular Characterization of Foodborne Pathogens
Title: The structural characterization of the O-polysaccharide antigen in the lipopolysaccharide of Escherichia coli serotype O118 and its relationship to the O-antigens of Salmonella enterica O47 and Escherichia coli serotype O151
Submitted to: Carbohydrate Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 2, 2010
Publication Date: October 15, 2010
Citation: Maclean, L.L., Liu, Y., Perry, M.B. 2010. The structural characterization of the O-polysaccharide antigen in the lipopolysaccharide of Escherichia coli serotype O118 and its relationship to the O-antigens of Salmonella enterica O47 and Escherichia coli serotype O151. Carbohydrate Research. 345:2664-2669.
Interpretive Summary: The bacterium, Escherichia coli, causes a variety of diseases in humans and animals, and the different E. coli are classified into what are referred to as serogroups. The diversity in the lipopolysaccharide (LPS), a bacterial surface component, helps us to distinguish among different bacteria. Traditionally, a procedure called serotyping is used to distinguish among the ca. 170 different E. coli serogroups based on differences in the LPS. This procedure, which relies on the use of antibodies raised in rabbits against different surface polysaccharides of the bacteria, can only be performed in specialized laboratories, is labor intensive and may require several days to complete, and one antiserum can react with multiple E. coli serogroups, rendering identification of the specific strain of E. coli difficult. Thus, simple, rapid, and reliable methods for detection and identification of different E. coli serogroups are needed. To characterize the surface polysaccharide of an important pathogenic E. coli belonging to serogroup O118, its LPS structure was determined. Results showed that the structure of the O118 LPS was consistent with the available genetic information, and interestingly, it was identical to the LPS structure of Salmonella enterica O47. It was also structurally related to the E. coli O151 LPS. These results suggest that E. coli O118, O151, and Salmonella enterica O47 may share a common ancestor. Characterization of the LPS structure provides a molecular reference for E. coli serotyping allowing more accurate identification of pathogenic E. coli O118.
Mild acid hydrolysis of the lipopolysaccharide produced by Escherichia coli O118:H16 (standard reference strain; NRCC 6613) contained an O-polysaccharide (O-PS) composed of D-galactose, 2-acetimidoylamino-2,6-dideoxy-L-galactose (L-FucNAm), 2-acetamido-2-deoxy-D-glucose, ribitol, and phosphate (1:1:1:1:1). Sugar analysis, one- and two-dimensional NMR spectroscopy, and sequential Smith-type periodate oxidation studies, indicated that the O-PS was determined to be an unbranched linear polymer of a repeating unit having the structure: '6)-a-D-Galp-(1'3)-a-L-FucpNAm-(1'3)-ß-D-GlcpNAc-(1'2)-Ribitol-5-P-O- The structure of the O-PS is consistent with the reported DNA data on the O-antigen gene-cluster of E. coli O118 and interestingly, the O-PS is identical to the structure of the O-antigen of Salmonella enterica O47, that also contains the unusual ribitol phosphate and 2-acetimidoylamino-2,6-dideoxy-L-galactose components. The E. coli O118 O-antigen is also structurally related to the O-antigen of E. coli O151:H10 strain 880-67, as predicted from the results of DNA sequencing of their respective O-antigen gene-clusters.