Detection Of Pathogenic Vibrio Parahaemolyticus In Aquatic Products

Vibrio parahaemolyticus is an important microorganism pathogen for food intoxication cases. Previous studies had reported that 5% of Vibrio parahaemolyticus were pathogenic, whereas more than 95% of isolates were nonpathogenic. Thus, it is essential to distinguish pathogenic Vibrio parahaemolyticus isolates from nonpathogenic ones. Kanagawa- phenomenon test had ever been used for identification of pathogenic Vibrio parahaemolyticus. Bur it is too complicated to be repeatable. Thermostable direct hemolysin, which is encoded by tdh gene had been regarded as the virulence factor for this bacterium. The detection of tdh gene can be used to reflect the patogenicity of Vibrio parahaemolyticus. This method had not yet been applied in China. We established a 16S rDNA test for characterization of Vibrio parahaemolyticus isolates and a tdh polymerase chain reaction for identification of pathogenic Vibrio parahaemolyticus isolates. These tests's abilities of identifying pathogenic Vibrio parahaemolyticus were compared with Kanagawa hemolysin test or urease test. Thirty-six of 39 Vibrio parahaemolyticus isolates (92.30%) so far tested by 16S rDNA were identified as Vibrio parahaemolyticus, concordant with the results from biochemistry tests. None of 181 clinical bacteria isolates was misclassified to be Vibrio parahaemolyticus. tdh positive rate of Vibrio parahaemolyticus isolates from diarrhea patients was 83.51%, higher than 13.70% of isolates from environments (p < 0.001). We had established a real-time PCR for quantitating tdh copy level. Final copies could be calculated by a formula y = -3.144 logx+43.229 (R = 0.997, P < 0.001, y = Ct values, x= copies of templates).