The aim of the study was the serological and structural characterization of the lipopolysaccharide (LPS) O antigen from P. mirabilis Dm55 coming from the urine of a patient from Lodz. The Dm55 LPS was recognized in ELISA only by the O54 antiserum, suggesting a serological distinction of the Dm55 O antigen from all the 84 Proteus LPS serotypes described. The obtained polyclonal rabbit serum against P. mirabilis Dm55 reacted in ELISA and Western blotting with a few LPSs (including O54), but the reactions were weaker than those observed in the homologous system. The LPS of P. mirabilis Dm55 was subjected to mild acid hydrolysis, and the obtained high-molecular-mass O polysaccharide was chemically studied using sugar and methylation analyses, mass spectrometry, and 1H and 13C NMR spectroscopy, including 1H,1H NOESY, and 1H,13C HMBC experiments. The Dm55 O unit is a branched three-saccharide, and its linear fragment contains α-GalpNAc and β-Galp, whereas α-GlcpNAc occupies a terminal position. The Dm55 OPS shares a disaccharide epitope with the Proteus O54 antigen. Due to the structural differences of the studied O antigen from the other described Proteus O polysaccharides, we propose to classify the P. mirabilis Dm55 strain to a new Proteus O85 serogroup.

Lipopolysaccharide, NMR, O polysaccharide, Proteus mirabilis, serological classification, antiserum, cross-reacting LPS

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,3,2	Ac	175.6	23.3
3,3	aDGlcpN	95.6	54.7	72.2	70.6	71.9	62.2
3	bDGalp	105.9	70.3	78.7	66.4	76.0	65.8
2	Ac	175.6	23.3
	aDGalpN	98.4	49.7	79.2	69.8	71.8	62.2


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,3,2	Ac	-	2.04
3,3	aDGlcpN	5.04	3.97	3.82	3.74	4.13	3.76
3	bDGalp	4.53	3.62	3.66	4.06	3.62	3.66-4.06
2	Ac	-	2.04
	aDGalpN	4.99	4.36	4.04	4.29	4.03	3.76


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,3,2	Ac		23.3/2.04
3,3	aDGlcpN	95.6/5.04	54.7/3.97	72.2/3.82	70.6/3.74	71.9/4.13	62.2/3.76
3	bDGalp	105.9/4.53	70.3/3.62	78.7/3.66	66.4/4.06	76.0/3.62	65.8/3.66-4.06
2	Ac		23.3/2.04
	aDGalpN	98.4/4.99	49.7/4.36	79.2/4.04	69.8/4.29	71.8/4.03	62.2/3.76

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]OC[C@H]1O[C@@H](O[C@@H]2[C@@H](NC(C)=O)[C@@H]([*])O[C@H](CO)[C@@H]2O)[C@H](O)[C@@H](O[C@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@H]2NC(C)=O)[C@H]1O

568.529 g/mol (C₂₂H₃₆R₂N₂O₁₅, R = next and previous repeats, not counted in mol weight)

The aim of the study was the serological and structural characterization of the lipopolysaccharide (LPS) O antigen from P. mirabilis Dm55 coming from the urine of a patient from Lodz. The Dm55 LPS was recognized in ELISA only by the O54 antiserum, suggesting a serological distinction of the Dm55 O antigen from all the 84 Proteus LPS serotypes described. The obtained polyclonal rabbit serum against P. mirabilis Dm55 reacted in ELISA and Western blotting with a few LPSs (including O54), but the reactions were weaker than those observed in the homologous system. The LPS of P. mirabilis Dm55 was subjected to mild acid hydrolysis, and the obtained high-molecular-mass O polysaccharide was chemically studied using sugar and methylation analyses, mass spectrometry, and 1H and 13C NMR spectroscopy, including 1H,1H NOESY, and 1H,13C HMBC experiments. The Dm55 O unit is a branched three-saccharide, and its linear fragment contains α-GalpNAc and β-Galp, whereas α-GlcpNAc occupies a terminal position. The Dm55 OPS shares a disaccharide epitope with the Proteus O54 antigen. Due to the structural differences of the studied O antigen from the other described Proteus O polysaccharides, we propose to classify the P. mirabilis Dm55 strain to a new Proteus O85 serogroup.

Lipopolysaccharide, NMR, O polysaccharide, Proteus mirabilis, serological classification, antiserum, cross-reacting LPS

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]OC[C@H]1O[C@H](O[C@H]2[C@@H](OP(=O)(O)OC[C@H](O)CO)[C@@H](CO)O[C@@H](O[C@@H]3[C@@H](NC(C)=O)[C@@H]([*])O[C@H](CO)[C@@H]3O)[C@@H]2O)[C@H](NC(C)=O)[C@@H](O)[C@@H]1O

722.587 g/mol (C₂₅H₄₃R₂N₂O₂₀P, R = next and previous repeats, not counted in mol weight)