Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 522/C1 and the international type strain from Escherichia coli O178

The structure of the O-antigenic polysaccharide (PS) from the enteroaggregative Escherichia coli strain 522/C1 has been determined. Component analysis and H-1 and C-13 NMR spectroscopy techniques were used to elucidate the structure. Inter-residue correlations were determined by H-1, H-1-NOESY and H-1, C-13-heteronuclear multiple-bond correlation experiments. The PS is composed of pentasaccharide repeating units with the following structure: -> 4)-alpha-D-GlcpNAc-(1 -> 4)-alpha-D-GalpA-(1 -> 2)-beta-D-Ribf-(1 -> 4)-beta-D-Galp-(1 -> 3)-beta-D-GalpNAc-(1 -> Analysis of NMR data reveals that on average the PS consists of four repeating units and indicates that the biological repeating unit contains an N-acetylgalactosamine residue at its reducing end. Serotyping of the E coli strain 522/C1 showed it to be E coli O178:H7. Determination of the structure of the O-antigen PS of the international type strain from E coli O178:H7 showed that the two polysaccharides have identical repeating units. In addition, this pentasaccharide repeating unit is identical to that of the capsular polysaccharide from E coli O9:K38, which also contains O-acetyl groups. (c) 2005 Elsevier Ltd. All rights reserved.