The First Report on the Structure of Polysaccharide Surface Antigens of the Clinical 0.062 Strain and the Contribution in the Serological Cross-Reactions.

bacilli co-form the human intestinal microbiota, but in favorable conditions, they may also affect immunocompromised individuals, causing urinary tract infections, bacteremia, or antibiotic-associated hemorrhagic colitis. The growing numbers of clinical outbreaks of . infections make these bacteria an emerging pathogen, which is still masked by the predominant . isolates. Thus, it is very important to advance knowledge on . pathogenicity. This work aims to characterize a urine isolate, . 0.062, from central Poland, which appears to present a multidrug-resistant and extended-spectrum β-lactamases-positive phenotype. The structural experiments include sugar and methylation analyses, mass spectrometry, and H and C Nuclear Magnetic Resonance (NMR) spectroscopy. Additionally, H,H ROESY, and H,C HMBC experiments were carried out on the high-molecular-weight O polysaccharide fraction of . lipopolysaccharides (LPSs). These analyses led to the detection of two polysaccharide antigens: one neutral, containing a linear trisaccharide unit called mannan, and one acidic, which is built up of a branched tetrasaccharide unit containing two mannopyranose (α-Man) residues, one galactopyranose (β-Gal) residue, and one galacturonic acid (α-GalA) residue. The GalA residue seems to be a potential minor epitope, recognized by the selected antisera in the serological studies.