Development of a Latex Agglutination Test for the Rapid Identification of Vibrio parahaemolyticus.

A latex agglutination test for the rapid identification of Vibrio parahaemolyticus has been developed. Two bacterial outer membrane proteins, with molecular weights of 36,000 and 34,000, were obtained by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis and were subsequently used as antigens for producing antibodies in rabbits. Immunoelectron microscopy demonstrated that the two proteins were present in the outer membrane of the microorganism. Latex particles sensitized with the affinity-purified antibodies were used as a reagent for the rapid identification of the bacterium. Of 173 strains (including 94 isolates of V. parahaemolyticus , 40 isolates of other vibrios and 39 strains of other bacteria) tested, the false-negative and false-positive rates were 1.4 and 3.1%, respectively. Some strains of three vibrios ( V. alginolyticus , V. harveyi , and V. mimicus ) produced false-positive results. However, no cross-reactions were observed with the latex reagent among the 39 strains (33 species) of other bacteria. It is proposed that suspicious colonies (green or blue) of V. parahaemolyticus on thiosulfate-citrate-bile salts-sucrose agar (TCBS) be subcultured to tryptic soy agar with 3% NaCl for overnight incubation. Cultures grown on tryptic soyagar-3% NaCl may be used for latex agglutination and galactosidase assays. V. parahaemolyticus will be latex positive and galactosidase negative. Under this condition, V. parahaemolyticus can be identified in only one day after suspect colonies were observed on TCBS agar.