Structural Masquerade of Plesiomonas shigelloides Strain CNCTC 78/89 O-Antigen—High-Resolution Magic Angle Spinning NMR Reveals the Modified d-galactan I of Klebsiella pneumoniae

Abstract

The high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR) analysis of Plesiomonas shigelloides 78/89 lipopolysaccharide directly on bacteria revealed the characteristic structural features of the O-acetylated polysaccharide in the NMR spectra. The O-antigen profiles were unique, yet the pattern of signals in the, spectra along with their 1H,13C chemical shift values, resembled these of d-galactan I of Klebsiella pneumoniae. The isolated O-specific polysaccharide (O-PS) of P. shigelloides strain CNCTC 78/89 was investigated by 1H and 13C NMR spectroscopy, mass spectrometry and chemical methods. The analyses demonstrated that the P. shigelloides 78/89 O-PS is composed of →3)-α-d-Galp-(1→3)-β-d-Galf2OAc-(1→ disaccharide repeating units. The O-acetylation was incomplete and resulted in a microheterogeneity of the O-antigen. This O-acetylation generates additional antigenic determinants within the O-antigen, forms a new chemotype, and contributes to the epitopes recognized by the O-serotype specific antibodies. The serological cross-reactivities further confirmed the inter-specific structural similarity of these O-antigens.

Structural Studies of the Lipopolysaccharide Isolated from Plesiomonas shigelloides O22:H3 (CNCTC 90/89)

“…The core OS of P. shigelloides 90/89 is similar to the previously reported core oligosaccharide of P. shigelloides strain CNCTC 78/89 [22], differing only by one sugar residue in the outer core, that is the 6-substituted Glc instead of the 6-substituted GlcN. In the core OS of P. shigelloides O33 [20], both glycoforms, containing 6-substituted GlcN or 6-substituted Glc and O-acetylation of the terminal GalNAc, were reported.…”

“…Structural analysis indicated that the core OS ( Figure 1 a,d and Table 1 ) is similar to the previously identified core oligosaccharide of P. shigelloides strain CNCTC 78/89 [ 22 ]. Both structures were undecasaccharides and differed by only one sugar residue in the outer core region.…”

“…P. shigelloides serovar O22:H3 (strain CNCTC 90/89) was obtained from the collection of the Institute of Hygiene and Epidemiology, Prague, Czech Republic. Bacteria were grown and harvested as described previously [ 22 ].…”

“…Structures of the 13 O-specific polysaccharides have been elucidated to date for strains 22074, 12254 [ 12 ], and AM36565 [ 13 ], and serotypes O51 [ 14 ], O17 [ 15 , 16 ], O1 [ 17 , 18 , 19 ], O33 [ 20 ], O24 [ 21 ], O12 [ 22 ], O54 [ 23 ], O74 [ 24 ], O37 [ 25 ], and O36 [ 26 ]. The core oligosaccharides were elucidated for strains assigned to serotypes O13 [ 27 ], O17 [ 15 , 16 ], O1 [ 18 , 19 ], O33 [ 20 ], O24 [ 21 ], O12 [ 22 ], O54 [ 28 ], O74 [ 24 ], O37 [ 25 ], and O36 [ 26 ], including its linkage to the O-specific polysaccharide for most of them. The lipid A region, as a part of the complete LPS structure, was elucidated for O54 [ 29 ], O74 [ 30 ], O37 [ 25 ], and O36 [ 26 ] serotypes.…”

“…To date, complete or partial LPS structures have been elucidated only for 15 strains out of 102 identified O-serotypes [11]. Structures of the 13 O-specific polysaccharides have been elucidated to date for strains 22074, 12254 [12], and AM36565 [13], and serotypes O51 [14], O17 [15,16], O1 [17][18][19], O33 [20], O24 [21], O12 [22], O54 [23], O74 [24], O37 [25], and O36 [26]. The core oligosaccharides were elucidated for strains assigned to serotypes O13 [27], O17 [15,16], O1 [18,19], O33 [20], O24 [21], O12 [22], O54 [28], O74 [24], O37 [25], and O36 [26], including its linkage to the O-specific polysaccharide for most of them.…”