斜带石斑鱼病原菌(哈维氏弧菌)的分离与鉴定

Isolation and identification of pathogenetic Vibrio harveyi from estuary cod Epinephelus coioides

从患病斜带石斑鱼 (Epinepheluscoioides)肝脏组织分离到EcGY0 2 0 4 0 1菌株 ,经人工感染、回归感染实验证实为致病菌。通过API系统和菌体常规形态特征、培养特性和生理生化反应指标测定以及 16SrRNA测序分析等综合鉴定 ,Ec GY0 2 0 4 0 1菌株为弧菌属哈维氏弧菌 (Vibrioharveyi) ,其半致死剂量LD50 为 2 .7× 10 6CFU/g鱼体重。药敏试验结果表明 ,EcGY0 2 0 4 0 1菌株对利福平、四环素。

An outbreak of serious mortality among the cultured estuary cods, Epinephelus coioides, characterized by an ulcer on the surface of moribund estuary cods’ body, occurred in Guangdong in April, 2003. One strain EcGY020401 was isolated from the liver of diseased estuary cod. Traditional physiological and biochemical methods, together with API system were applied in the bacterial classification. This strain was incubated with tryptic soy agar (TSA) supplemented with 0.85% NaCl and thiosulfate citrate bile sucrose agar(TCBS). As a result, it is negative and shows yellow in TCBS. There is no ornithine ecarboxylase, arginine dihydrolase, Lysine decarboxylase, Urease and so on in the strain. There is cellobiose, sorbitol, glucose and sucrose in the strain. The strain was confirmed to be the pathogen causing the disease in E. coioides through artificial infection test. The LD_(50) value of the strain for estuary cod was 2.7×10~6 CFU/g estuary cod body weight (using Reed-Muench method). The bacteria was reisolated from liver after bacterial challenge. To determine the status of strain EcGY020401, the strain’s 16S rRNA sequence was analyzed by Vectlr NTI suit 6.0 software. The results showed the reisolated strain is the same species as strain EcGY020401. The results also showed that 16S rRNA sequence length of strain EcGY020401 is 1 379 bp. A system evolution tree was set up, showing strain EcGY020401 is the nearest to V.harveyi. Concolusionly, strain EcGY020401 belongs to V.harveyi. This study demomstrated that strain EcGY020401 does not radiate,which is not agreeable with reported resources. In addition, this study showed that strain EcGY020401 does not grow when salinity is 0 while it grows very well when salinity changes from 15 to 100. In conclusion, the strain is salinity-trophile. The test of sensitivities of strain EcGY020401 to 20 kinds of antibiotics revealed that the pathogen is sensitive to drugs such as Rifampixcin(RA), tetracycline(TE) and Ceftriaxone(CRO).