The O antigen of Klebsiella pasteurii 0.067 lipopolysaccharide: structure, serology and genetic loci organization.

Klebsiella pasteurii belongs to Klebsiella oxytoca species complex and corresponds to the Ko4 phylogroup, which was recently recognized as a distinct species. Its reliable identification requires whole-genome sequencing and chromosomal blaOXY variants characteristic of the Ko4 phylogroup can support species-level differentiation. K. pasteurii is isolated from soil, water, plants, animals and human. The recent description of the species as a distinct species has resulted in limited knowledge regarding its virulence factors including O-polysaccharide (OPS). The presented studies focus on a K. pasteurii 0.067 isolate from the urine of a newborn. The strain phenotypic characterization revealed an antibiotic-sensitivity profile and extended spectrum β-lactamases (ESBL)-negative phenotype. The K. pasteurii 0.067 genome sequence analysis revealed the presence of four genes associated with drug resistance (oqxAB, fosA and blaOXY-4-1), kleboxymycin and yersiniabactin encoding genes. Genomic analysis revealed type O2α locus with additional wbbYZ and gml2β clusters. Structural analysis, supported by NMR spectroscopy and mass spectrometry indicated the presence of the O1αβ,2αβ OPS of K. pasteurii 0.067 with non-stoichiometric substitution of terminal β-d-Galp with 3,4-linked S-pyruvic acid (3,4(S)-Pyr), which provides potential epitope recognized by Proteus mirabilis O24 antiserum. It is the first report on the K. pasteurii O antigen structure and its genetic background.