养殖大菱鲆腹水病病原的研究

Studies on the Characteristics of Pathogenic Edwardsiella tarda Isolated from Diseased Scophthalmus maximus

从患腹水病的大菱鲆（Scophthalmus maximus）肝和腹水中分离得到优势菌株CW-7，人工感染证实该菌株对大菱鲆幼苗有较强的致病性，腹腔注射1．4×10^3cfu／尾，即可引起感染鱼100％的死亡，症状与自然发病鱼相似；病原菌为革兰氏染色阴性，直杆状（0．4～0．8）×（0．6～2．0）μm，周生鞭毛运动，氧化酶阴性，兼性厌氧菌，兼具葡萄糖氧化和发酵（O／F）2种代谢途径，其生理生化特征与迟缓爱德华氏菌（Edzvardsiella tarda）一致；对该菌的16SrDNA序列克隆、测序后在GenBank中进行了序列对比分析，结果与迟缓爱德华氏菌的序列高度一致（99．92％），进化树分析表明属于同一类群，确定该菌株为迟缓爱德华氏菌（Edzvardsiella tarda）。该菌株对庆大霉素、卡那霉素、多粘菌素B等14种抗生素敏感，而对青霉素、萘啶酸、复方新诺明等14种药物均具有抗性。

A dominated strain CW-7 was isolated from the liver and ascites of juvenile turbot （Scophthalmus maximus ） with ascites disease. Challenge test showed that the isolate CW-7 was highly pathogenic to juvenile turbot. The mortality of the fish was 100 % injected with a dosage 1.4 × 10^3 cfu of CW-7 per fish. The same clinical signs as those of naturally infected turbot appeared in the injected ones. The strain was facuhatively anaerobic, having both a respiratory and a fermentative type of metabolism. It is gram-negative, rod-shaped （0.4-0.8） × （0.6-2.0）μm, with peritrichous flagella, and without producing oxidase. The strain are similar in characteristics to Edwardsiella tarda. The sequence of 16SrDNA of the strain CW-7 was compared to the seguences in the GenBank database. It shared high similarity to that of Edwardsiella tarda. The strain CW-7 was identified to be EdwardsieUa tarda. It was sensitive to 14 kinds of antibiotics such as gentamicin, kanamycin, and polymyxin B, but resistant to 14 other kinds of antibiotics.