Structural and Serological Characterization of Yet Another New O Antigen, O86, in Proteus mirabilis Clinical Strains

Area of Science:

• Microbiology
• Immunology
• Structural Chemistry

Background:

• Bacteria of the genus Proteus are significant human pathogens, particularly affecting the urinary tract and wounds.
• Eighty-five O serogroups have been identified within the Proteus genus.
• Proteus mirabilis Bprz 86, isolated from a patient fistula, did not fit existing serogroups.

Purpose of the Study:

• To characterize the lipopolysaccharide (LPS) and O-specific polysaccharide (O antigen) of Proteus mirabilis Bprz 86.
• To determine the serological relationship between P. mirabilis Bprz 86 and other Proteus strains.
• To propose a new O serogroup for Proteus based on structural and serological data.

Main Methods:

• Enzyme-Linked Immunosorbent Assay (ELISA) and Western blotting were used for serological analysis.
• Mild acid degradation of LPS was performed to isolate the O-specific polysaccharide.
• Nuclear Magnetic Resonance (NMR) spectroscopy (1D and 2D 1H and 13C) was employed for structural elucidation.

Main Results:

• P. mirabilis Bprz 86 shares a common epitope with Proteus O17 antigens.
• The O-specific polysaccharide of P. mirabilis Bprz 86 contains a unique six-constituent repeating unit.
• This repeating unit includes (R)-3-hydroxybutanoyl, fucosamine, and glucose residues, forming a fragment also found in O17 antigens.
• P. mirabilis Bprz 86 was found to be identical to another clinical isolate, P. mirabilis Sm 120.

Conclusions:

• The serological and chemical data support the characterization of P. mirabilis Bprz 86.
• The two studied P. mirabilis isolates (Bprz 86 and Sm 120) are proposed as candidates for a new Proteus O serogroup, O86.