Chemical and Serological Properties of Lipopolysaccharides from Vibrio parahaemolyticus O‐Untypeable Strains Isolated from Patients

Abstract

Chemical and serological studies have been carried out on the O-antigenic lipopolysaccharides (LPS) of six strains, U-6443, W-90144, X-3972, AD-7999, 90A-6611 and KX-V212, of Vibrio parahaemolyticus isolated from patients. The O-serotypes of these strains have not been identified because they were not agglutinated by any diagnostic antisera against known O-serotype strains. A compositional sugar analysis of their LPS revealed that out of the six O-untypeable (OUT) strains, U-6443, W-90144 and AD-7999 strains belonged to chemotype II (chemotype of O2), 90A-6611 and KX-V212 strains to chemotype III (chemotype of O3, O5, 011 and O13) and X-3972 strain to chemotype IV (chemotype of O4). A structural analysis of LPS isolated from KX-V212 revealed that the inner core region of the LPS consisted of only one mole of 2-keto-3-deoxy-D-manno-octonic acid, which carried a phosphate group at position C4 and the outer core at position C5. In passive hemolysis tests performed by using LPS as the antigen to sensitize sheep red blood cells (SRBC), and diagnostic antisera (O1 to O11) or anti-whole-cell rabbit antisera raised against O12, O13 and the six OUT strains, strong cross-reactivity was observed among LPS derived from the strains belonging to chemotype II (U-6443, W-90144, AD-7999 and O2). Strong cross-reactivity was also observed between X-3972 (chemotype IV) and O4 LPS. In contrast, LPS from two of the strains belonging to chemotype III (90A-6611 and KX-V212) did not react with any of the antisera raised against known O-serotypes. Cross-absorption tests showed that the O-antigens of U-6443, W-90144 and AD-7999 were identical to that of O2, and the O-antigen of X-3972 to that of O4. On the other hand, after the absorption of antisera raised against 90A-6611 and KX-V212 with O2 cells, the hemolytic activities against SRBC sensitized with homologous LPS were still retained at a high titer, whereas the hemolytic activities against SRBC sensitized with LPS from other O-serotype strains were completely eliminated. A cross-absorption test revealed that the O-antigens of these two strains were identical to each other. Thus, it was demonstrated that the O-serotype of OUT strains 90A-6611and KX-V212 was not involved in the known O-serotypes; rather it represented a novel serotype which has not hitherto been reported. Key words : Lipopolysaccharide, LPS, Vibrio parahaemolyticus, OUT strainsThe halophilic bacterium Vibrio parahaemolyticus is a causative agent of food poisoning associated primarily with sea products. V parahaemolyticus is presently divided into 11 or 13 O-serotypes based on agglutination and agglutinin absorption tests (10,11,17,20). The Oantigens of Gram-negative bacteria are lipopolysaccharides (LPS) that are amphipathic macromolecules located on bacterial cell surfaces. Serological O-specificity of Gram-negative bacteria is attributed to the chemical structure of the polysaccharide portion constituting LPS molecules. The polysaccharide portions of LPS from usual enteric bacteria such as Salmonella and Es...

A review of the current status of cultural and rapid detection of Vibrio parahaemolyticus

“…, 1995). The reason for this discrepancy may arise from the fact that the O‐serotypes of many strains have not been identified because they are not agglutinated by diagnostic antisera against known O‐serotype strains (Hashii et al. , 2000), and many strains remain untypeable (Kaysner & DePaola, 2004).…”

“…, 2000), and many strains remain untypeable (Kaysner & DePaola, 2004). Compositional sugar analysis was evaluated by Hashii et al. (2000) to characterise the lipopolysaccharide of six untypeable (OUT) strains, and the study found that the O‐serotype of two of the OUT strains employed was not a previously known O‐serotype and represented a new serotype that had not been earlier reported.…”

“…Earlier, however, a thirteenth O group was identified and characterised (Hisatsune et al, 1993;Iguchi et al, 1995). The reason for this discrepancy may arise from the fact that the O-serotypes of many strains have not been identified because they are not agglutinated by diagnostic antisera against known O-serotype strains (Hashii et al, 2000), and many strains remain untypeable (Kaysner & DePaola, 2004). Compositional sugar analysis was evaluated by Hashii et al (2000) to characterise the lipopolysaccharide of six untypeable (OUT) strains, and the study found that the O-serotype of two of the OUT strains employed was not a previously known O-serotype and represented a new serotype that had not been earlier reported.…”

Development of Kaptive databases for Vibrio parahaemolyticus O- and K-antigen genotyping

“…parahaemolyticus serotyping, but frequently V. parahaemolyticus strains are not agglutinated by any diagnostic antisera against known serotypes and are, therefore, not typable [3, 5–7]. For several pathogenic bacterial species, e.g.…”

Development of Kaptive databases for Vibrio parahaemolyticus O- and K-antigen serotyping

“…Many V. parahaemolyticus serotypes have been identified as pandemic clones, and certain serotypes, for example O3:K6, O1:KUT and O4:K68, are generally considered to be more virulent than others (Jones et al 2012; Nair et al 2007). Agglutination tests are the gold standard for V. parahaemolyticus serotyping but frequently, V. parahaemolyticus strains are non-typable with agglutination tests in routine screening (Gavilan, Zamudio, and Martinez-Urtaza 2013; Gil et al 2007; Hashii et al 2000; Jones et al 2012). For several pathogenic bacterial species, e.g.…”