Bacteria from the genus Proteus are facultative human pathogens, primarily attacking the urinary tract and wounds. A total of 85 O serogroups have been identified so far among these bacilli. P. mirabilis Bprz 86 was isolated from the fistula of a patient in Łódź, Poland. Enzyme-Linked Immunosorbent Assay (ELISA) and Western blotting studies involving the P. mirabilis Bprz 86 lipopolysaccharide (LPS) and the strain-specific rabbit antiserum indicated that the strain, which does not belong to any of the O1-O85 serogroups, shares a common epitope with Proteus O17 antigens and is identical to another clinical P. mirabilis strain, Sm 120, isolated from the urine of a patient in the area. The O-specific polysaccharide (O antigen) was obtained from P. mirabilis Bprz 86 LPS through mild acid degradation, and the six-constituent structure of its repeating unit was determined using chemical analyses and 1D and 2D 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy. It includes (R)-3-hydroxybutanoyl, which, along with fucosamine and glucose residues, forms a fragment also present in the O17 antigens. Based on the obtained serological and chemical data, the two studied P. mirabilis isolates were proposed as candidates for a new successive O serogroup in the genus Proteus, O86.
Keywords: (R)-3-hydroxybutanoic acid; O-specific polysaccharide; chemical structure; epitope; lipopolysaccharide; serotyping.