Structure of the O-specific polysaccharide of Proteus mirabilis D52 and typing of this strain to Proteus serogroup O33

The acidic O-specific polysaccharide chain (O-antigen) of the lipopolysacch aride (LPS) of Proteus mirabilis strain D52 was studied using chemical anal yses along with H-1-NMR and C-13-NMR spectroscopy, including 2D COSY, TOCSY , ROESY, H-detected H-1, C-13 and H-1, P-31 HMQC experiments. The polysacch aride was found to contain D-ribitol 5-phosphate (D-Rib-ol-5-P) and ethanol amine phosphate (Etn-P) and has the following structure: [GRAPHIC] This structure is identical with that of the O-polysaccharide of R mirabili s o33 strain 59/57, and, hence, P. mirabilis D52 belongs to the same Proteu s serogroup O33. Serological studies with O-antiserum against P. mirabilis D52 confirmed this but showed that the LPS species of P. mirabilis 59/57 an d D52 are not identical, having different epitopes in the core region. A se rological crossreactivity of P. mirabilis D52 O-antiserum was observed with LPS of two other Proteus strains, P. mirabilis O16 and P. penneri 103, whi ch have structurally different O-polysaccharides. The role of charged group s, Rib-ol-5-P and Etn-P in the immunospecificity is discussed.