Structural and Serological Studies of the O6-Related Antigen of <i>Aeromonas veronii</i> bv. <i>sobria</i> Strain K557 Isolated from <i>Cyprinus carpio</i> on a Polish Fish Farm, which Contains <span style="font-variant: small-caps">l</span>-perosamine (4-amino-4,6-dideoxy-<span style="font-variant: small-caps">l</span>-mannose), a Unique Sugar Characteristic for <i>Aeromonas</i> Serogroup O6
oleh: Katarzyna Dworaczek, Dominika Drzewiecka, Agnieszka Pękala-Safińska, Anna Turska-Szewczuk
| Format: | Article |
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| Diterbitkan: | MDPI AG 2019-07-01 |
Deskripsi
Amongst <i>Aeromonas</i> spp. strains that are pathogenic to fish in Polish aquacultures, serogroup O6 was one of the five most commonly identified immunotypes especially among carp isolates. Here, we report immunochemical studies of the lipopolysaccharide (LPS) including the O-specific polysaccharide (O-antigen) of <i>A. veronii</i> bv. <i>sobria</i> strain K557, serogroup O6, isolated from a common carp during an outbreak of motile aeromonad septicemia (MAS) on a Polish fish farm. The O-polysaccharide was obtained by mild acid degradation of the LPS and studied by chemical analyses, mass spectrometry, and <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy. It was revealed that the O-antigen was composed of two O-polysaccharides, both containing a unique sugar 4-amino-4,6-dideoxy-<span style="font-variant: small-caps;">l</span>-mannose (<i>N</i>-acetyl-<span style="font-variant: small-caps;">l</span>-perosamine, <span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc). The following structures of the O-polysaccharides (O-PS 1 and O-PS 2) were established: O-PS 1: →2)-α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc-(1→; O-PS 2: →2)-α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc-(1→3)-α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc-(1→3)-α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc-(1→. Western blotting and an enzyme-linked immunosorbent assay (ELISA) showed that the cross-reactivity between the LPS of <i>A. veronii</i> bv. <i>sobria</i> K557 and the <i>A. hydrophila</i> JCM 3968 O6 antiserum, and <i>vice versa</i>, is caused by the occurrence of common α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc-(1→2)-α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc and α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc-(1→3)-α-<span style="font-variant: small-caps;">l</span>-Rha<i>p</i>4NAc disaccharides, whereas an additional →4)-α-<span style="font-variant: small-caps;">d</span>-Gal<i>p</i>NAc-associated epitope defines the specificity of the O6 reference antiserum. Investigations of the serological and structural similarities and differences in the O-antigens provide knowledge of the immunospecificity of <i>Aeromonas</i> bacteria and are relevant in epidemiological studies and for the elucidation of the routes of transmission and relationships with pathogenicity.