Vibrio parahaemolyticus, a causative bacterium of food poisoning unique for its particular primary association with sea products, is now divided serologically into 11 or 12 O-forms based on agglutination and agglutinin-absorption tests. We determined the sugar composition of the somatic O-antigens, i.e., lipopolysaccharides (LPS), of representative strains of each O-form.Of particular interest is the absence of evidence for the presence of 2-keto-3-deoxy-octonic acid (KDO), a regular sugar component of gram-negative bacterial LPS, in any LPS examined, with the exception of 06. Furthermore, 07 and 012 LPS contained a KDO-like compound that is, however, not identical with KDO. Glucose, glucosamine, and L-glycero-D-mannoheptose were found as common sugar constituents. Three unidentified amino sugars, designated here as P1, P2, and P3, were found. Various combinations of each of these unidentified amino sugars, and of galactose, fucose, arabinose, D-glycero-D-mannoheptose, galactosamine, KDO, and the KDO-like substance were detected in accordance with the O-form of LPS. On the basis of the sugar composition, LPS of the 12 O-forms of V. parahaemolyticus can be classified into nine chemotypes, because 03, 05, and 011 LPS belong to the same chemotype and 07 and 012 to another chemotype.

A comparative study of the sugar composition of O-antigenic lipopolysaccharides (LPS) isolated from Vibrio alginolyticus and those from V. parahaemolyticus was carried out. 3-DeoxY-D-mannooctulosonic acid, 2-keto-3-deoxy octonate (KDO), a regular sugar constituent of gram-negative bacterial LPS, was totally absent from LPS of all V. alginolyticus strains examined as it was from those of V. parahaemolyticus. Furthermore, a KDO-like thiobarbituric acid test-positive substance, identical with that of either V. parahaemolyticus 07 or 012, was also found in LPS from three strains, 505-78, 905-78, and 1013-79 (designated tentatively as group I), out of the five strains of V. alginolyticus tested. LPS from the members of group I contained, as component sugars, glucose, galactose, r-glycero-n-mannoheptose, glucosamine, galactosamine, the KDO-like substance, and an unidentified amino sugar PI. Thus, LPS of the members of group I possessed a similar sugar composition which is similar to that of LPS from either V. parahaemolyticus 07 or 012. LPS of strain 1027-79, one of the other two strains (designated tentatively as gorup II), contained as component sugars, glucose, t-glycero-n-mannoheptose, glucosamine, galactosamine, and the other unidentified amino sugar P2, while LPS of strain 53-79, the other member of group II, contained galactose as an additional component. The results indicate that LPS of strain 1027-79 has a sugar composition similar to that of V. parahaemolyticus 09 LPS.Vibrio alginolyticus, a halophilic marine bacterium, is distinguished from V. parahaemolyticus, the causative agent of infectious food poisoning, on the basis of growth in peptone containing 7 and 10% NaCl, Voges-Proskauer reaction, sucrose and arabinose fermentation (16), and pathogenicity causing the food poisoning (23).In our previous study (7), the sugar composition of lipopolysaccharides (LPS) isolated from all 12 O-serotypes of V. parahaemolyticus was determined qualitatively and quantitatively. Of particular interest was the lack of evidence for the presence of 3-deoxY-D-mannooctulosonic acid, 2-keto-3-deoxy octonic acid (KDO), a regular sugar component of gram-negative bacterial LPS (14), in V. parahaemolyticus LPS, with the exception of 06 LPS. Furthermore, a KDO-like thiobarbituric acid testpositive substance was instead found in 07 and 012 LPS.