Structural and Serological Characterization of the O Antigen of Proteus mirabilis Clinical Isolates Classified into a New Proteus Serogroup, O84

Abstract

Two closely related Proteus mirabilis smooth strains, Kr1 and Ks20, were isolated from wound and skin samples, respectively, of two infected patients in central Poland. Serological tests, using the rabbit Kr1-specific antiserum, revealed that both strains presented the same O serotype. Their O antigens are unique among the Proteus O serotypes, which had been described earlier, as they were not recognized in an enzyme-linked immunosorbent assay (ELISA) by a set of Proteus O1-O83 antisera. Additionally, the Kr1 antiserum did not react with O1-O83 lipopolysaccharides (LPSs). The O-specific polysaccharide (OPS, O antigen) of P. mirabilis Kr1 was obtained via the mild acid degradation of the LPSs, and its structure was established via a chemical analysis and one- and two-dimensional 1H and 13C nuclear magnetic resonance (NMR) spectroscopy applied to both initial and O-deacetylated polysaccharides, where most β-2-acetamido-2-deoxyglucose (N-acetylglucosamine) (GlcNAc) residues are non-stoichiometrically O-acetylated at positions 3, 4, and 6 or 3 and 6, and a minority of α-GlcNAc residues are 6-O-acetylated. Based on the serological features and chemical data, P. mirabilis Kr1 and Ks20 were proposed as candidates to a new successive O-serogroup in the genus Proteus, O84, which is another example of new Proteus O serotypes identified lately among serologically differentiated Proteus bacilli infecting patients in central Poland.

Antigenic and Structural Properties of the Lipopolysaccharide of the Uropathogenic Proteus mirabilis Dm55 Strain Classified to a New O85 Proteus Serogroup

“…To date, such characterization has been performed for ten Proteus spp. strains infecting patients from central Poland and isolated from different sources, among which four isolates were found as uropathogenic P. mirabilis [13,14,20]. Urine was the most common source (43%) of Proteus spp.…”

“…So far, the Proteus spp. isolates from the patients living in central Poland have been classified into seven newly formed Proteus O serogroups, O77-O82 and O84, among which group O78 appeared to be the most numerous [13,14]. The uniqueness of the OPS structure of the P. mirabilis Dm55 LPS also concerns the number of components in the O-repeating unit since a branched three-saccharide unit has been found so far only in two Proteus O serotypes (O6 and O13) [11].…”

“…Thus, it is crucial to gain a better knowledge of the OPS structure and epitope specificity, which are also a basis for serological classification of the strains to an appropriate O serogroup. To date, the Proteus classification scheme includes 84 O serogroups and 11 R serogroups, which are still being updated and completed with new representatives [13,14]. In this work, we report on a new OPS structure and the serological specificity of the P. mirabilis Dm55 LPS obtained from the isolate coming from a patient from central Poland.…”

Lipopolysaccharides: Regulated Biosynthesis and Structural Diversity

“…Thus, this Special Issue presents eight manuscripts that cover the regulation of LpxC [21,33], the targeting of LpxC to design vaccines with reduced endotoxicity [34], structural diversity in the composition of LPS and non-stoichiometric modifications in lipid A [35][36][37][38], and the LPS-neutralizing activity of BPI proteins [39].…”

“…Two studies address specific LPS structural alterations in the plant pathogenic bacterium Pectobacterium parmentieri and the human pathogen Proteus mirabilis [37,38]. In the study on P. parmentieri, the heterogeneity of the O-polysaccharides (OPS) of two strains was examined by chemical composition analysis and NMR spectroscopy.…”