Haemophilus parasuis is a Gram-negative bacterium from the family Pasteurellaceae and a swine pathogen. H. parasuis is found in the upper respiratory tract of piglets and produces Glasser's disease, an invasive disease characterized by polyserositis. H. parasuis contains a short lipopolysaccharide (LPS) or lipooligosaccharide (LOS) reported to play a partial role in interaction with host cells. The presence of capsule has been phenotypically demonstrated in certain H. parasuis strains and its role in virulence has been suggested, but the chemical structure of the surface polysaccharides of this bacterium was unknown. The structure of capsular polysaccharide (CPS) and LOS from virulent strains ER-6P and Nagasaki was studied by NMR spectroscopy, mass spectrometry and chemical methods. CPS from both strains had the same main chain with disaccharide repeating unit, substituted with α-Neu5R-(2-3)-α-GalNAc-(1-P-(strain ER-6P) or α-Neu5R-(2-3)-α-Gal-(1-P-strain Nagasaki) side chains, where R is the N-acetyl or N-glycolyl group. Glycolyl-neuraminic acid is widely found in animal glycoproteins, but it apparently has not been found in bacteria before, and might be important for the biology of this microorganism. Ac and Gc were present in equal amounts in the strain ER-6P but Nagasaki contained only about 20% of Gc substituent. Both strains produced the same LPS of a rough type with a single phosphorylated Kdo linking core and lipid A parts. LOS structure was similar to some strains of H. influenzae and contained a globotetraose terminal sequence.

Lipopolysaccharide, polysaccharide, capsule, Haemophilus parasuis

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,6,0	aDGalp	96.5	69.1	70.0	70.1	72.9	62.0
3,6	P
3	bDGlcp
2	Ac
4	Ac
	bDFucpN4N


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,6,0	aDGalp	5.54	3.85	3.90	4.03	4.11	3.75
3,6	P
3	bDGlcp
2	Ac
4	Ac
	bDFucpN4N


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,6,0	aDGalp	96.5/5.54	69.1/3.85	70.0/3.90	70.1/4.03	72.9/4.11	62.0/3.75
3,6	P
3	bDGlcp
2	Ac
4	Ac
	bDFucpN4N

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

632.509 g/mol (C₂₂H₃₇R₂N₂O₁₇P, R = next and previous repeats, not counted in mol weight)