Abstract
We studied the incidence of Vibrio parahaemolyticus sporadic diarrhea, the distribution of thermostable direct hemolysin (TDH) gene (tdh) - and TDH-related hemolysin (TRH) gene (trh) -positive V. parahaemolyticus, and the molecular epidemiological relationship between V. parahaemolyticus isolated from patients and the sea environment in the Tohoku district in northeastern Japan. V. parahaemolyticus sporadic diarrhea was prevalent in August 1999 in the Tohoku district. A marked rise in the temperature of sea water was observed in mid July in Aomori, Akita, and Miyagi prefectures, followed by an increase in the number of sporadic V. parahaemolyticus patients, suggesting that the rise in the temperature of sea water could serve as an indication for V. parahaemolyticus sporadic diarrhea cases. Serotyping of 1, 265 V. parahaemolyticus strains isolated from patients across the Tohoku district revealed that O3:K6 was the predominant serotype, representing 86.8% of the total isolates. O3: Kut trh + was isolated from sea mud in Miyagi prefecture, and O3:K6 tdh + and O3:K7 tdh + were isolated from sea mud in Fukushima prefecture, confirming that tdh- and trh-positive V. parahaemolyticus strains are disseminated in the sea environment of the Tohoku district. V. parahaemolyticus O3:K6 tdh + strains isolated from sea mud in Fukushima prefecture showed Type A Notl PFGE pattern, which was the predominant type among strains isolated from patients in Fukushima prefecture, suggesting an etiologic role of environmental V. parahaemolyticus O3:K6 tdh + in human disease.
Dynamics of tdh- and trh-positive V. parahaemolyticus strains in the environment should be further elucidated to better understand the epidemiology of V. parahaemolyticus O3:K6 tdh + infection, including the mechanism of food contamination with tdh- and trh-positive V. parahaemolyticus strains from environmental sources.
