Structure of a Kdo-containing O polysaccharide representing Proteus O79, a newly described serogroup for some clinical Proteus genomospecies isolates from Poland.

Abstract From 41 Proteus genomospecies strains isolated in Poland, seven displayed similar serospecificity in ELISA with intact and adsorbed O antisera as well as in Western blot. The cross-reacting strains were found to belong to Proteus genomospecies 5/6 and classified into a new Proteus serogroup, O79, which seems to be widespread among Proteus genomospecies clinical isolates in Lodz, Poland. The O polysaccharide of the lipopolysaccharide of a representative O79 strain, 11 B-r, was studied by chemical analyses and 1 H and 13 C NMR spectroscopy, and the following structure of the repeating unit was established: →4)-α- d -Glc p NAlaAc-(1→5)-α-Kdo p -(2→2)-α- d -Glc p -(1→3)-β- d -Glc p NAc-(1→ where AlaAc indicates N -acetyl- l -alanyl and Kdo indicates 3-deoxy- d - manno -oct-2-ulosonic acid. The O polysaccharide was unstable under mild acidic conditions and cleaved by acid-labile linkages of Kdo residues to yield a tetrasaccharide with Kdo at the reducing end. The structure established is unique among Proteus O polysaccharides, which is in agreement with the lack of any significant cross-reactivity for the lipopolysaccharide of strain 11 B-r and O antisera against strains of all known Proteus O serogroups and vice versa.