豹纹鳃棘鲈类结节症病原的分离鉴定

为查明养殖豹纹鳃棘鲈类结节症的病因,自患病豹纹鳃棘鲈内脏中分离到1株优势菌株061101,人工感染试验证实,该菌具有强毒力,能够引起被感染鱼内脏出现白色结节并死亡,为引起此次豹纹鳃棘鲈类结节症的病原菌。采用形态学、生化特性测定对菌株061101进行鉴定,同时采用细菌16S rRNA通用引物进行PCR扩增得到该菌的16S rRNA基因序列,测序后比对,构建系统发育树。试验结果表明,菌株061101与发光杆菌属中的美人鱼发光杆菌杀鱼亚种基本特征相符;基于16S rRNA基因序列构建的系统发育树将菌株061101与美人鱼发光杆菌杀鱼亚种聚为一支,置信度达100%。据此确定,此次豹纹鳃棘鲈类结节症的病原为美人鱼发光杆菌杀鱼亚种。药敏结果显示,该菌株仅对链霉素(300μg/片)、庆大霉素(120μg/片)敏感,对多黏菌素B、阿洛西林等中度敏感,对氟苯尼考、恩诺沙星、强力霉素等均耐药。

Isolation and Identification of Pathogen in Leopard Coraltrout Plectropomus leopardus with Nodular Disease

A Gram-negative bacterium (designated as strain 061101) was isolated from the kidney and spleen of leopard coraltrout Plectropomus leopardus with nodular disease,and was virulent for healthy leopard coraltrout challenged by intraperitoneal injection,with lethal dose (LD 50 ) of 9.49×10^4 cfu/mL. Both 16S rRNA gene sequence and phylogenetic analysis revealed that strain 061101 had high similarity to Photobacterium damselae ssp. piscicida ,which agreed with the results of morphological,physiological and biochemical identification. The antibiotic sensitivity test indicated that strain 061101 was susceptible to streptomycin (300 μg/disc) and gentamicinum (120 μg/disc),and high resistant to enrofloxacin,florfenicol,and doxycycline.