条石鲷(Oplegnathus fasciatus)源美人鱼发光杆菌杀鱼亚种(Photobacterium damselae subsp. piscicida)的分离鉴定

2013年浙江省舟山市某网箱养殖条石鲷(Oplegnathus fasciatus)暴发了一种严重的疾病,病鱼主要症状为脾、肾出现1-2 mm的白色类结节.从患病鱼内脏处分离得到1株优势菌OF-1,经人工感染实验证实为此次引起条石鲷死亡的致病菌,半数致死量为5.93×104 CFU/g.形态学观察结果显示,菌株OF-1为革兰氏阴性、短杆状,在TCBS培养基上不生长.API 20E细菌鉴定系统、16S rRNA系统发育树分析结果证实,该菌株为美人鱼发光杆菌杀鱼亚种(Photobacterium damselae subsp.piscicida).该菌对庆大霉素、青霉素、氟哌酸、氧氟沙星、氨苄青霉素等药物高度敏感,对红霉素、链霉素、卡那霉素、苯唑青霉素等药物具有抗性.

Isolation and Identification of Photobacterium damselae subsp. piscicida from Diseased Rock Bream (Oplegnathus fasciatus)

Rock bream (Oplegnathus fasciatus) is an important economic fish cultured in China.In recent years,rock bream aquaculture has developed rapidly along the coast of China.In August 2013,an epizootic occurred among cultured rock bream in a cage culture farm in Zhoushan of Zhejiang Province,China,which caused a cumulative mortality up to 20％.The diseased fish had no obvious symptoms on body surface;the main symptom was characterized by many white nodules (1-2 mm) in the spleen and kidney.The aim of this research was to isolate and identify the bacterial isolate,then to determine the pathogenicity and test drug sensitivity of bacteria pathogen found in diseased rock bream.A dominant bacterium strain OF-1 was isolated from the liver,spleen and kidney.Artificial infection test with intraperitoneal injection method proved that the LDs0 value of bacterium strain OF-1 was 5.93 × 104 CFU/g.It was identified based on the morphology,the biochemical characteristics,and the 16S rRNA sequencing.The results of morphological tests indicated that strain OF-1 was gram-negative,rod bacteria and did not grow in the TCBS plate.OF-1 exhibited an API 20E index profile of 2005004,which was identical with the profile exhibited by Photobacterium damselae subsp.piscicida.The sequence analysis of 16S rRNA gene,the morphological,physiological and biochemical characteristics indicated that the bacterium strain OF-1 could be identified as P.damselae subsp.piscicida.The strain was highly sensitive to gentamicinum,penicillin C, norfloxacin,ofloxacin and ampicillin,but was resistant to erythromycinum,vancomycin,rocephin,streptomycin,kanamycinum and proctaphlin.This paper reported for the first time that P.damselae subsp.Piscicida caused the disease of rock bream in China,which will provide reference in fish health management and disease control.