双斑东方鲀皮肤溃烂症病原菌鉴定及药敏分析

Identification and drug sensitivity analysis of pathogenic bacteria causing skin ulceration disease of Takifugu bimaculatus

摘要:

【背景】2016年6月福建省海水鱼类苗种繁育科研中试基地养殖的双斑东方鲀出现皮肤溃烂症，病鱼特征为：游动缓慢，停止摄食，口角、表皮、鳍条溃烂，肾脏、脾脏充血严重。【目的】对发生皮肤溃烂症双斑东方鲀病原进行鉴定，以期为该疾病有效防治提供技术支撑。【方法】从濒死病鱼肾脏、脾脏和病灶部位肌肉组织分离出优势菌株，经人工肌肉注射感染证实其为致病菌。经菌株形态学、生理生化特征分析、16S rRNA基因序列分析和系统发育树构建等手段综合鉴定并进行药敏分析。【结果】从患病鱼体脾脏分离得到一株优势菌株SBDFT-1#，人工感染实验证实为致病菌。结合形态、生理生化和分子生物学鉴定确定该菌为哈维氏弧菌(Vibrio harveyi)，该菌为革兰氏阴性菌，极生单鞭毛，呈短杆状，菌体大小0.9×2.0 μm。该菌株在2216E平板培养基菌落呈乳白色，边缘透明，中间凸起；在TCBS培养基菌落呈黄色，边缘整齐，中央隆起。该菌对苯唑西林、头孢噻肟、氧氟沙星、链霉素、复方新诺明、多粘菌素B等14种抗生素敏感，对氨苄西林、青霉素、四环素、麦迪霉素等9种抗生素耐药。【结论】哈维氏弧菌是海水养殖经济鱼类的常见致病菌，但从患病双斑东方鲀体内分离出属首次报道，对防治双斑东方鲀皮肤溃烂症具有积极的指导意义。

Abstract:

[Background] In June 2016, Takifugu bimaculatus, cultured in Fujian Seawater Fish Seedling Breeding Research Base, outbroke the skin ulceration disease. The main symptoms of diseased fishes were characterized by slow swimming, lack of appetite, ulceration of mouth, epidermis and fins, and severe hyperemia of kidneys and spleen. [Objective] Identify the pathogenic, and provide the technical support for effectively preventing and treating skin ulceration in T. bimaculatus farming. [Methods] The dominant strains were isolated from the kidney, spleen and muscle tissue of diseased fish. The strains were confirmed to be a pathogenic bacterium by artificial intramuscular injection. The strains were identified by morphological, physiological and biochemical characteristics analysis, 16S rRNA gene sequence analysis, phylogenetic tree construction, and drug sensitivity analysis. [Results] The dominant strain SBDFT-1# was isolated from spleen of diseased fish, and was confirmed to be pathogenic strain of the skin ulceration disease. Strain SBDFT-1# was identified as Vibrio harveyi, with the morphological indexes of Gram-negative, single-flagellate, short rod-shaped, and a cell size of 0.9×2.0 μm. The colony of strain SBDFT-1# was milky white and yellow on the 2216E and TCBS plate medium, respectively, which were both central bulge and neat-transparent edges. Strain SBDFT-1# was sensitive to 14 antibiotics including Oxacillin, Cefotaxime, Ofloxacin, Streptomycin, Co-trimoxazole and Polymyxin B; while strain SBDFT-1# was resistant to 9 antibiotics such as Ampicillin, Penicillin, Tetracycline and Medecamycin. [Conclusion] This is the first report of V. harveyi as a pathogenic strain, isolated from the diseased T. bimaculatus, while it is a common pathogen in the economical fish farming. The study has a positive significantly guiding for the prevention and treatment of skin ulceration of T. bimaculatus.