UREA HYDROLYSIS AND SUPPRESSED PRODUCTION OF THERMOSTABLE DIRECT HEMOLYSIN (TDH) BY VIBRIO-PARAHAEMOLYTICUS ASSOCIATED WITH PRESENCE OF TDH-RELATED HEMOLYSIN GENES

A total of 18 strains of V. parahaemolyticus isolated from patients of past food poisoning cases occurring in Kanagawa Prefecture, Japan, we re assayed for presence of the thermostable direct hemolysin (TDH) gen e and the TDH-related hemolysin (TRH) genes (trh 1 and trh 2) with spe cific reference to their ability to hydrolyze urea and TDH production. A polymerase chain reaction assay revealed that all urea-hydrolyzing strains (9 strains) carried either trh 1 gene or trh 2 gene. The strai ns carrying the trh genes as well as the tdh gene produced TDH less by a factor of 4 to 16 than those carrying only the tdh gene, suggesting the expression of the tdh gene was suppressed by the presence of trh gene through a mechanism yet to be defined.