Abstract:

Added together, 105 strains of Vibrio parahaemolyticus (Vp) were isolated from 273 aquatic products in three species collected from farmers’ markets in Shanghai. The average Vp contamination rate of aquatic products was 38.46%. In addition, the Vp contamination rates of crustacean, shellfish and fish were 50.96%, 27.12% and 15.79%, respectively. A significant difference was observed in three species of aquatic products (P＜0.01). Only tlh gene was detected in isolated Vp strains through multiplex-PCR, while no tdh gene and trh gene were detected. These isolated Vp strains exhibited strong resistance to 10 kinds of antibiotics including ceftriaxone, nalidixic acid and norfloxacin according the evaluation by K-B method. Some of these isolated Vp strains exhibited 69.50% resistance to ampicillin and 12.38% resistance to amoxicillin. Moreover, the analysis of plasmid DNA from 105 isolated strains revealed that seven isolated strains harbored 1－3 plasmids with size ranging from 1 to 24 kb. In analyzing fingerprinting images of plasmids and drug resistant types, no direct relationship between drug resistance and plasmid size or amount was observed. These results suggest that the drug resistance to these antibiotics mainly results from chromosomal mutation of Vp strains.

Key words: aquatic product, Vibrio parahaemolyticus (Vp), virulence gene, drug resistance, plasmid