Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 94/D4 and the international type strain Escherichia coli O82

The structure of the O-antigen polysaccharides (PS) from the enteroaggregative Escherichia coli strain 94/D4 and the international type strain E. coli O82 have been determined. Component analysis and H-1, C-13, and P-31 NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by H-1, C-13-heteronuclear multiple-bond correlation, and H-1, H-1-NOESY experiments. D-GroA as a substituent is linked via its O-2 in a phosphodiester-linkage to O-6 of the alpha-D-Glcp residue. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-alpha-D-Glcp6-(P-2-D-GroA)-(1 -> 4)-beta-D-Galp-(1 -> 4)-beta-D-Glcp-(1 -> 3)-beta-D-GlcPNAc-(1 -> Cross-peaks of low intensity from an alpha-D-Glcp residue were present in the NMR spectra and spectral analysis indicates that they originate from the terminal residue of the polysaccharicle. Consequently, the biological repeating unit has a 3-substituted N-acetyl-D-glucosamine residue at its reducing end. Enzyme immunoassay using specific anti-E. coli O82 rabbit sera showed identical reactivity to the LPS of the two strains, in agreement with the structural analysis of their O-antigen polysaccha rides. (C) 2009 Elsevier Ltd. All rights reserved.