Structures of the O-specific polysaccharides and a serological cross-reactivity of the lipopolysaccharides of Proteus mirabilis O24 and O29.

Strains of Proteus mirabilis belonging to serogroups O24 and O29 are frequent in clinical specimens. Anti-P. mirabilis O24 serum cross-reacted with the lipopolysaccharide (LPS) of P. mirabilis O29 and vice versa. The structures of the O-specific polysaccharides (OPSs, O-antigens) of both LPSs were established using sugar analysis and one- and two-dimensional 1H- and 13C-NMR spectroscopy and found to be different. SDS-PAGE and Western immunoblotting suggested that the serological cross-reactivity of the LPSs is due to a common epitope(s) on the core-lipid A moiety, rather than on the OPS. Therefore, the epitope specificity and the structures of the O-antigens studied are unique among Proteus serogroups.