澳洲龙纹斑源致病菌嗜水气单胞菌TPF-2的分离鉴定及药敏特性研究

Isolation and identification of Aeromonas hydrophila strain TPF-2 from murray cod(Maccullochella peelii peelii) and its antibiotic sensitivity

为查明浙江某养殖场导致澳洲龙纹斑暴发性死亡的病原,并提供有效的防控措施,本研究利用传统病原菌分离方法从该场患病澳洲龙纹斑肝脏、肾脏和腹水中均分离到1株优势菌,命名为TPF-2。采用形态学特征分析、16S r RNA基因序列分析、构建系统发育树并结合API全自动细菌鉴定仪对其进行鉴定,确定菌株TPF-2为嗜水气单胞菌(Aeromonas hydrophila)。菌株TPF-2人工回归感染试验结果显示,其对澳洲龙纹斑具有致病性,人工感染澳洲龙纹斑肝脏、肾脏等多个组织出现肿大充血等症状,且从其肝脏和肾脏中再次分离到相同的病原菌。菌株TPF-2在哥伦比亚血琼脂培养基上呈现β溶血现象。药敏试验显示,菌株TPF-2对先锋必素、菌必治、硫酸锌霉素、氟苯尼考、诺氟沙星、恩诺沙星6种药物敏感,对氨苄青霉素、多西环素、磺胺异恶唑等10种药物耐药。本研究首次发现嗜水气单胞菌可以感染引进的澳洲龙纹斑且具有较强的致病性,初步研究了该病原菌的生物学特性和药物敏感性,为澳洲龙纹斑嗜水气单胞菌病害的防治和澳洲龙纹斑高密度循环水健康养殖产业化提供了依据。

In order to identify the pathogen which caused a serious disease in a farmed murray cod (Maccullochella peelii peelii) farm of Zhejiang,a dominant bacterial strain,designated TPF-2,was isolated from the liver,kidney and ascites of diseased farmed murray cod by traditional method of pathogen isolation from the farm.The strain TPF-2 was identified as Aeromonashydrophila by means of the morphology features,the 16S rRNA gene sequence,phylogenetic tree analysis and the API automatic Microbial Identification System.The pathogenicity of the strain TPF-2was confirmed by the pathogenicity verification in healthy murray cod.The clinical signs of artificially infected fish were similar to that of the natural infected fish,with the symptoms of swelling and hemorrhage of hepar and kidney,and the same bacterium could be recovered from these infected murray cod.The strain was β hemolytic on the Colombian blood agar medium.The susceptibility test to antibiotics displayed that the strain TPF-2 from murray cod was susceptible to cefoperazone,rocephin,neomycin sulfate powder,flofenicol,norfloxacin and enoxacin,but resistant to other 10kinds of antibiotics including ampicillin,doxycycline and sulfamethoxazole.The study firstly demonstrated that A.hydrophila was able to infect introduced farmed murray cod and exhibited strong virulence to murray cod.Preliminary study on biological characteristics and antibiotic susceptibility of A.hydrophila would provide a basis information for control and prevention of the related diseases,and the industrialization of high intensive recirculating healthy aquaculture of murray cod.