半滑舌鳎皮肤溃疡病病原研究

为了对半滑舌鳎皮肤溃疡病的病原进行研究, 从患有严重皮肤溃疡病的半滑舌鳎病灶中分离病原菌, 并经人工感染确认病原。对引起此次疾病的病原菌的形态特征、理化特性、胞外产物酶活性与溶血活性及其对抗菌类药物的敏感性等生物学特性进行了研究和分析, 还测定了16 S rRNA、gyrB基因序列, 分析了相应序列的同源性并构建了系统发育树。结果从病灶中分离得到4株优势菌, 经人工注射感染证实菌株A3为引起养殖半滑舌鳎皮肤溃疡病的病原菌, 其半数致死量LD50为1.5×104.2 CFU/mL。其中, 16 S rRNA、gyrB在GenBank中的登录号分别是JN391271、JN168881。从基于16 S rRNA与gyrB基因序列构建的系统发育树看, 分离筛选出来的病原菌与哈维氏弧菌同源性最高, 结合生理生化特征和16 S rRNA、gyrB基因序列分析结果, 认为该病原菌为哈维氏弧菌。胞外产物酶活性及溶血活性检测结果表明，该病原菌具有淀粉酶、尿素酶、脂肪酶、蛋白酶和卵磷脂酶活性而不具有明胶酶活性, 在4%羊血TSA平板上呈β溶血活性。病原菌的药物敏感性试验结果显示, 该菌对四环素、强力霉素、诺氟沙星、磺胺异恶唑等敏感, 而对其他用于试验的抗生素敏感度低或具有一定的抗性。

Study on pathogen of skin ulcer disease of half-smooth tongue sole (Cynoglossus semilaevis)

The pathogen was isolated from lesion and was identified by artificial infection in order to in-vestigate the pathogen of skin ulcer of Cynoglossus semilaevis.The morphological,physiological and bio-chemical characteristics,and the activity of extracellular products and hemolysin and the the sensitivity to the antimicrobial agents were studied,the 16S rRNA and gyrB genes were partially sequenced and com-pared with sequences deposited in GenBank,and the molecular phylogenetic trees were constructed.Four strains of dominant bacteria associated with serious skin ulcers were isolated from half-smooth tongue sole,C.semilaevis.Bacterial strain A3 was proved to be a pathogen by muscle injection with bacteria suspension,and the LD50 was 1.5×104.2 CFU/mL.The GenBank accession no·was JN391271 and JN 168881 respec-tively of sequenced 16S rRNA gene and gyrB gene of isolate.16S rRNA and gyrB genes exhibited high similarity with Vibrio harveyi from GenBank database.The results of physiological and biochemical tests and molecular identification suggested that the pathogen was V.harveyi.Detection of the activity of ex-tracellular products and hemolysin showed that the strain could produce amylase,lipase,urease,lecithinase,proteinase and with β haemolysis in containing 4% defibrinated rabbit blood of TSA plates,but no gelati-nase.The results of drug resistance of the pathogen to 17 antimicrobial agents showed that the strain was sensitive to tetracycline,doxycycline,norfloxacin,sulfafurazole and so on,but lowly sensititve or resistant to other tested antimicrobial agents.