Citrobacter freundii OCU158 is a serologically cross-reactive strain with Escherichia coli O157:H7. To explore the close relationship between two strains, we have analyzed the chemical structures of O-specific polysaccharides and antigenic properties of lipopolysaccharides (LPSs) of both strains. The structure of O-specific polysaccharides from both strains was found to be identical by chemical and nuclear magnetic resonance analyses, in which D-PerNAc was 4-acetamido-4,6-dideoxy-D-mannose: [→4)-β-D-Glc-(1→3)-α-D-PerNAc-(1→4)-α-D-GalNAc-(1→3)-α-L-Fuc-(1→](n). The enzyme immunoassay using LPS derived either from E. coli O157 or from C. freundii could equally detect high levels of serum antibodies against LPS in patients with enterohemorrhagic E. coli (EHEC) O157 infection. Absorption of antibodies in EHEC patient serum by LPS from E. coli O157 or C. freundii, however, showed a difference in the epitopes. This difference was attributable to the epitope specificity of the core region and/or lipid A structure in LPS.

Lipopolysaccharide, structure, polysaccharide, property, Escherichia, Escherichia coli, Escherichia coli O157:H7, O-specific, O-specific polysaccharide, serologic, cross-reactivity, crossreactivity, Citrobacter, Citrobacter freundii, epitope specificity

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,4,3	bDGlcp	103.3	73.0	74.0	77.8	74.7	59.8
3,4,4	Ac	?	?
3,4	aDRhap4N	99.5	66.6	70.8	48.6	68.2	14.7
3,2	Ac	?	?
3	aDGalpN	100.2	52.9	67.8	77.7	?	60.9
	aLFucp	98.9	66.8	71.4	76.8	?	16.5


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,4,3	bDGlcp	4.42	3.16	3.42	3.67	3.38	3.76
3,4,4	Ac
3,4	aDRhap4N	4.95	4.18	3.92	4.12	4.07	1.01
3,2	Ac
3	aDGalpN	5.08	3.77	3.90	3.88	?	3.59
	aLFucp	4.80	3.74	3.69	3.95	3.57	1.03


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,4,3	bDGlcp	103.3/4.42	73.0/3.16	74.0/3.42	77.8/3.67	74.7/3.38	59.8/3.76
3,4,4	Ac	NMR TSV error 2: unequal length of 13C and 1H datasets
3,4	aDRhap4N	99.5/4.95	66.6/4.18	70.8/3.92	48.6/4.12	68.2/4.07	14.7/1.01
3,2	Ac	NMR TSV error 2: unequal length of 13C and 1H datasets
3	aDGalpN	100.2/5.08	52.9/3.77	67.8/3.90	77.7/3.88	?/?	60.9/3.59
	aLFucp	98.9/4.80	66.8/3.74	71.4/3.69	76.8/3.95	?/3.57	16.5/1.03

The spectrum also has 6 signals at unknown positions (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

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

698.672 g/mol (C₂₈H₄₆R₂N₂O₁₈, R = next and previous repeats, not counted in mol weight)