关键词: 大黄鱼, 溶藻弧菌, 致病性, 毒力基因, Large yellow croaker, Vibrio alginolyticus, 16SrDNA, acute toxicityty

Abstract: Vibriosis is the most prevalent and the most harmful marine disease of marine aquaculture animals. large yellow croaker (Pseudosciaena crocea) , the The largest aquaculture fish is the main infection of Vibrio. Body surface ulcers, hemorrhage, and silk rot are the main symptoms of vibriosis. In this study, a dominant strain was isolated from the diseased large yellow croaker of the Ningde Jiaocheng Dawan fish raft of China, which had surface and fin ulcer, hemorrhage and gill defect. In order to identify the strain and evaluate its pathogenicity, the culture was purified and the physiological and biochemical characteristics of the strain were analyzed. The 16SrDNA of the strain was identified, the pathogenicity of the strain to the large yellow croaker was determined, and the virulence factor of the strain was also tested. The culture results showed that the strain could grow on TCBS medium, and the colony color was yellow. The physiological and biochemical identification results indicated that the strain was Gram-negative Brevibacterium, which was halophilic, and the physiological and biochemical indexes were consistent with the standard strain 17700; 16SrDNA analysis results showed that the homology rate of the strain with Vibrio alginolyticus was 99%, and it was confirmed that the strain was Vibrio alginolyticus and named Val180620. The results of the challenge showed that the Val180620 strain had strong pathogenicity to the large yellow croaker. When injected at a water temperature of 25 °C, the LD50 of the large yellow croaker of the specification (20±2) g was 2.38×106 CFU. The results of virulence-related gene analysis indicated that the strain Val180620 carried virulence-related genes such as CollagenaseVA, ToxR, FlaA and TRH, which explained that the strain Val180620 has high pathogenicity and caused ulceration and bleeding of the diseased fish. In addition, the UreR gene was not detected in the strain Val180620, but the strain Val180620 showed high pathogenicity, the result indicated that the UreR gene maybe not the determinant of the virulence of Vibrio alginolyticus..