RESUMO
The lipopolysaccharides (LPS) of Proteus penneri 28 and Proteus vulgaris O31 (PrK 55/57) were degraded with dilute acetic acid and structurally identical high-molecular-mass O-polysaccharides were isolated by gel-permeation chromatography. Sugar analysis and nuclear magnetic resonance (NMR) spectroscopic studies showed that both polysaccharides contain D-GlcNAc, 2-acetamido-2,6-dideoxy-L-glucose (L-2-acetamido-2,6-dideoxyglucose (N-acetylquinovosamine)) and 2-acetamido-3-O-[(S)-1-carboxyethyl]-2-deoxy-D-glucose (N-acetylisomuramic acid) and have the following structure: [carbohydrate structure: see text] where (S)-1-carboxyethyl [a residue of (S)-lactic acid] (S-Lac) is an ether-linked residue of (S)-lactic acid. The O-polysaccharide studied is structurally similar to that of P. penneri 26, which differs only in the absence of S-Lac from the GlcNAc residue. Based on the O-polysaccharide structures and serological data of the LPS, it was suggested classifying these strains in one Proteus serogroup, O31, as two subgroups: O(31a), 31b for P. penneri 28 and P. vulgaris PrK 55/57 and O31a for P. penneri 26. A serological relatedness of the LPS of Proteus O(31a), 31b and P. penneri 62 was revealed and substantiated by sharing epitope O31b, which is associated with N-acetylisomuramic acid. It was suggested that a cross-reactivity of P. penneri 28 O-antiserum with the LPS of several other P. penneri strains is due to a common epitope(s) on the LPS core.
