The O-specific polysaccharide (OPS) isolated from the lipopolysaccharide of Proteus mirabilis O36 was found to have a pentasaccharide repeating unit of the following structure: →2)-β-D-Ribf-(1→4)-β-D-Galp-(1→4)-α-D-GlcpNAc6Ac-(1→4)-β-D-Galp-(1→3)-α-D-GlcpNAc-(1→. The structure is unique among Proteus OPS, which is in agreement with the classification of this strain into a separate Proteus O-serogroup. Remarkably, the P. mirabilis O36-polysaccharide has the same structure as the OPS of Escherichia coli O153, except that the latter is devoid of O-acetyl groups. The cross-reaction of anti-O36 antibodies with the O-part of E. coli O153 lipopolysaccharide is observed. In the present study, two steps of serotyping Proteus strains are proposed: screening of dry mass with enzyme-linked immunosorbent assay and immunoblot with the crude lipopolysaccharides. This method allowed serotyping of 99 P. mirabilis strains infecting the human urinary tract. Three strains were classified into serogroup O36. The migration pattern of these lipopolysaccharides fraction with long O-specific PSs was similar to the standard laboratory P. mirabilis O36 (Prk 62/57) lipopolysaccharide. The relatively low number of clinical strains belonging to serogroup O36 did not correspond to the presence of anti-P. mirabilis O36 antibodies in the blood donors' sera. Twenty-five percent of tested sera contained a statistically significant elevated level of antibodies reacting with thermostable surface antigens of P. mirabilis O36. The presence and amount of antibodies correlated with Thr399Ile TLR4 polymorphism types (P=0.044).

Escherichia coli, O-specific polysaccharide, Proteus mirabilis, serological classification, bacterial polysaccharide structure, TLR4

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,4,4,4	bDRibf	108.2	80.3	71.4	84.1	64.0
3,4,4	bDGalp	104.7	72.4	74.2	77.3	76.0	62.6
3,4,2	Ac	175.6-175.9	23.3-23.4
3,4	aDGlcpN	99.2	54.9	70.5	79.8	72.1	60.8
3	bDGalp	105.0	71.9	73.4	77.9	77.3	61.7
2	Ac	175.6-175.9	23.3-23.4
	aDGlcpN	97.2	53.9	81.5	70.0	73.4	61.9


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,4,4,4	bDRibf	5.32	4.26	4.28	4.11	3.69-3.87
3,4,4	bDGalp	4.52	3.52	3.79	4.02	3.76	3.77
3,4,2	Ac	-	2.05-2.06
3,4	aDGlcpN	4.85	3.95	3.95	3.77	4.30	3.82-3.92
3	bDGalp	4.53	3.58	3.73	3.98	3.75	3.72-3.74
2	Ac	-	2.05-2.06
	aDGlcpN	5.10	4.19	4.05	3.65	3.94	3.84-3.88


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,4,4,4	bDRibf	108.2/5.32	80.3/4.26	71.4/4.28	84.1/4.11	64.0/3.69-3.87
3,4,4	bDGalp	104.7/4.52	72.4/3.52	74.2/3.79	77.3/4.02	76.0/3.76	62.6/3.77
3,4,2	Ac		23.3-23.4/2.05-2.06
3,4	aDGlcpN	99.2/4.85	54.9/3.95	70.5/3.95	79.8/3.77	72.1/4.30	60.8/3.82-3.92
3	bDGalp	105.0/4.53	71.9/3.58	73.4/3.73	77.9/3.98	77.3/3.75	61.7/3.72-3.74
2	Ac		23.3-23.4/2.05-2.06
	aDGlcpN	97.2/5.10	53.9/4.19	81.5/4.05	70.0/3.65	73.4/3.94	61.9/3.84-3.88

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@H]1[C@H](O[C@@H]2[C@H](O)[C@@H](O)[C@H](O[C@H]3[C@H](O)[C@@H](NC(C)=O)[C@@H](O[C@@H]4[C@H](O)[C@@H](O)[C@H](O[C@H]5[C@H](O)[C@@H](CO)O[C@H](*)[C@@H]5NC(C)=O)O[C@@H]4CO)O[C@@H]3CO)O[C@@H]2CO)O[C@H](CO)[C@H]1O

862.785 g/mol (C₃₃H₅₄R₂N₂O₂₄, R = next and previous repeats, not counted in mol weight)