Vilulence Characteristics And Molecular Typing Of Vibrio Parahaemolyticus Strains Isolated From Clinical Patients And Environment In Hangzhou, China

Vibrioparahaemolyticus , frequently found in marine water and seafoods, is a gram-negative halophilica bacterium and a major pathogen associated with food poisoning and gastroenteritis in coastal region of China. Recently many molecular epidemiology studies revealed that a new O3:K6 V. parahaemolyticus strains with tdh positive and trh negative have caused a pandemic of gastroenteritis at least in Asia and America. V. parahaemolyticus strains found in environments are often not pathogenic to humans, and the relationship between strains from clinic and environment is being studied now.Food poisoning caused by V. parahaemolyticus strains is frequent in Hangzhou, a coastal city in eastern China. It is important for prevention and control of food poisoning to understand the serotypies, virulence, and molecular characteristics of V. parahaemolyticus strains from clinic and environments. In this study, the V. parahaemolyticus strains from food poisoning patients, sporadic diarrhea patients and seafoods in Hangzhou during 2000 and 2001 were serotypied and tested forthermostable direct hemolysin gene (tdh) and thermostable direct hemolysin-related hemolysin gene (trh), which are considered as two main virulences in V. parahaemolyticus, using PCR. Moreover, the molecular characteristics of O3:K6 serovar strains found in this study were showed using ribotyping, random amplified polymorphic DNA analysis(RAPD), enterobacterial repetitive intergenic consensus PCR(ERIC - PCR).It was found that the tdh was positive in 92 out of 94 V. parahaemolyticus strains from food poisoning patients and in 33 out of 34 strains from sporadic diarrhea patients, and trh was not detected in all above clinical strains. Meanwhile the tdh was negative in all V. parahaemolyticus strains from environments (seafoods), and the trh was also negative except one strain with the activity of urease. All strains with trh negative had no activity of urease. It is suggested that the V. parahaemolyticus strains from food poisoning patients and sporadic diarrhea patients in Hangzhou are almost tdh positive and trh negative and the V. parahaemolyticus strains with tdh negative and trh positive in environment might be a potential pathogen in Hangzhou.It was also found that the serotype distribution among V. parahaemolyticus strains from clinic and environments was distinctive. The V. parahaemolyticus O3:K6 strains with tdh positive and trh negative caused 11 out of 13 food poisoning events (84.6%), while O4:K8 serovar strains with tdh positive and trh negative were responsible for other two events (15.4%). The O3:K6, O4:K8, and Ol :K? serovar strains were dominantly found in sporadic diarrhea patients, with proportion of 26.5%, 17.7%, and 38.2% respectively. However, serotypes of V. parahaemolyticus strains from seafood, in which O3:K6 or O4:K8 was not found, were more divergent than those from clinic. The fingerprints of ribotyping, RAPD, and ERIC -PCR suggest that the V. parahaemolyticus O3:K6strains with tdh positive and trh negative from clinic belonged to a closed related clone. The fingerprints between O3:K6 strains from clinic and O3:K? strains from environment were distinctive. The results above suggest that an close related O3:K6 V. parahaemolyticus strains with tdh positive and trh negative prevail dominantly in Hangzhou. Summarily, in this study the serotypes, virulences, and molecular characteristics of V. parahaemolyticus strains from clinic and environments in Hangzhou were understood somewhat.