Genetic and biochemical characteristics of Vibrio parahaemolyticus caused hepatic kidney necrosis disease in groupers raising in Cat Ba, Hai Phong

Abstract

Vibrio parahaemolyticus bacteria causes hepatic kidney necrosis disease in several marine fish species having highly economic value. From a number of the diseased groupers collecting in Cat Ba, Hai Phong, 6 bacterial strains having typically morphological and biochemical characteristics
of V. parahaemolyticus species were identified. All these 6 bacterial strains resisted to 5 studied antibiotics, particularly resisted strongly to ampicillin. The survival rate of Epinephelus coioides (orange spot grouper) after 14 days of experimental infection with 6 bacterial strains was 2.2% to 18.89% at dose of 100 μl/fish, 107 CFU/ml. The result of analyzing the presence of haemolysin virulent genes showed that there were 2 toxR and tlh genes in all 6 isolated strains. The tdh and trh genes were not detected in genome of 6 isolated strains. The full sequences of toxR and tlh genes were amplified with the corresponding sizes were 879 bp and 1254 bp with 2 self-design primers (toxR2- toxR4 and tlh1-tlh3). This studied result is basis for the further researches on gene mutation, space structure, pathogen mechanisms of proteins coding from 2 these toxicity genes.