Re-classification within the serogroups O3 and O8 of Citrobacter strains.

Background: Citrobacter strains are opportunistic pathogens often responsible for serious enteric as well as extra-intestinal diseases, and therefore the O-antigenic scheme, still in use in diagnostic identification, should be set for proper serotyping. The structures of more than 30 different Citrobacter O-antigens (O-polysaccharide chains of the lipopolysaccharides) of 43 Citrobacter O-serogroups have been elucidated so far. However, relationships between strains in several heterogeneous serogroups still need to be clarified by immunochemical studies.

Structure of the O-polysaccharide of Providencia alcalifaciens O35 containing an N-[(S)-1-carboxyethyl]-L-alanine (alanopine) derivative of 4-amino-4,6-dideoxyglucose.

The O-polysaccharide of Providencia alcalifaciens O35 was studied by sugar and methylation analyses along with (1)H and (13)C NMR spectroscopy, including 2D (1)H,(13)C HMBC, and NOESY experiments in D2O and, to detect correlations for NH protons, in a 9:1 H2O/D2O mixture. A unique N-(1-carboxyethyl)alanine (alanopine, Alo) derivative of 4-amino-4,6-dideoxyglucose (Qui4N) was identified as the polysaccharide component. Alanopine was isolated by solvolysis of the polysaccharide with triflic acid followed by acid hydrolysis, and its (2S,4S)-configuration was determined by the specific optical rotation.

Structure of the O-polysaccharide of Edwardsiella tarda PCM 1156.

Mild acid degradation of the lipopolysaccharide of Edwardsiella tarda PCM 1156 afforded an O-polysaccharide, which was isolated by gel-permeation chromatography on Sephadex G-50 and studied by sugar and methylation analyses along with (1)H NMR and (13)C NMR spectroscopy, including 2D (1)H,(1)H COSY, TOCSY, ROESY, (1)H,(13)C HSQC, and HMBC experiments. The following structure of the linear tetrasaccharide repeating unit of the O-polysaccharide was established: [structure: see text].

Structure of the O-polysaccharide of Edwardsiella tarda PCM 1150 containing an amide of D-glucuronic acid with L-alanine.

Mild acid degradation of the lipopolysaccharide of Edwardsiella tarda PCM 1150 afforded an O-polysaccharide, which was isolated by GPC on Sephadex G-50 and studied by sugar and methylation analyses along with 1D and 2D 1H and 13C NMR spectroscopies, including experiments performed in a 9:1 H2O/D2O mixture to detect NH protons and their correlations with CH protons. The O-polysaccharide was found to contain an amide of d-glucuronic acid with l-alanine (d-GlcA6Ala) and the following structure of the branched hexasaccharide repeating unit was established: -->4)-β-D-GlepA6Ala-(1-->4)-α-L-Fucp-(1-->4)-α-D-Glcp-(1-->4)-α-D-Quip-(1-->3)-β-D-GlcpNAc-(1-->3<--1α-D-GalpNAc.