引起养殖许氏平鲉死亡的鳗利斯顿氏菌的分离鉴定及致病性

Isolation, identification and pathogenicity of Listonella anguillarum from diseased cultured Sebastes schlegelii

从患病许氏平鲉的病灶处分离得到一株优势菌,记为SS-1。通过两点背部肌肉注射进行人工感染实验,证明该菌对健康许氏平鲉的半数致死浓度为9.6×106CFU/mL,可感染许氏平鲉的多种内脏和组织。细菌形态学和生理生化特征测定结果显示,菌株SS-1为革兰氏阴性,短杆状,极生单鞭毛;氧化酶阳性、接触酶阳性、硝酸盐还原阳性、吲哚产生阳性、V-P试验阳性、精氨酸双水解酶阳性、H2S产生阴性等,与鳗利斯顿氏菌特征相符。16S rRNA基因序列分析结果表明,该菌与鳗利斯顿氏菌的同源性达到了99%,因此,将菌株SS-1鉴定为鳗利斯顿氏菌。

Sebastes schlegelii is an important economic fish cultured in North China. In recent years, S. schlegelii aquaculture has developed rapidly along the northern coast of China. The expansion and intensi- fication of S.schlegelii farming has led to the occurrence of some diseases. In August 2011, an epizootic occurred among cultured S.schlegelii in a cage culture farm in Qingdao, which caused cumulative mortality rate 30%. To make certain the causative pathogen, we studied the etiology and virulence of S. schlegelii so as to provide basic data for the farming industry of S. schlegelii. In this study, we used the morphological, physiological and biochemical methods to identify the isolated bacterium. Meanwhile, to ensure the results accurately, the phylogenetic analyses were also used. A dominant bacterium strain SS-1 was isolated from the skin, gill, liver, spleen, kidney of the diseased S. schlegelii. Artificial infection test with intramuscular injection method proved that the median lethal concentration （LCs0） value of bacterium strain SS-1 in S. schlegelii was 9.6~ 106 CFU/mL. This bacterium could cause severe infections in several tissues and organs of the fish. The results of morphological, physiological ＆ biochemical characteristics tests showed that strain SS-1 was gran-negative, rod bacteria, polar flagellum, and the results of oxidase, contact enzyme, nitrate reduction, producing indol, V-P test and arginine digydrolase test were positive; producing H2S test was negative. The morphological, physiological ＆ biochemical characteristics indicated that SS-1 could be identified as Listonella anguillarum. The sequence analysis of 16S rRNA gene of strain SS-1 was identical with L. anguillarum and the homogeneity is 99%. This paper reported for the first time that L. anguillarum caused the disease of S. schlegelii in China, which will provide reference in fish health management and disease control.