半滑舌鳎病原菌(发光杆菌杀鱼亚种)的分离与鉴定

Isolation of Photobacterium damselae subsp. piscicida from diseased tongue sole (Cynoglossus semilaevis Gunther) in China

摘要:

2006年夏,山东青岛某渔场养殖半滑舌鳎(Cynoglossus semilaevis Gunther)大量死亡。症状主要表现为体表溃烂,鳍基部出血等,解剖可见胆囊发黑,肾脏发黄。从患病半滑舌鳎胆囊分离出优势菌并命名为WY06。人工感染试验证实WY06对半滑舌鳎及模式动物斑马鱼都具有很强的致病性,其半数致死量分别为5.5×10³cfu/克鱼(5.2×10⁵cfu/条鱼)和1.9×10³cfu/克鱼(8.9×10²cfu/条鱼)。该病原菌革兰氏染色阴性,菌体呈杆状。综合该菌在形态、生理生化特征及16S rDNA同源性等方面的结果,确认WY06为美人鱼发光杆菌杀鱼亚种(Photobacterium damselae subsp.piscicida)。该菌对头孢呋肟、菌必治等抗生素敏感。美人鱼发光杆菌杀鱼亚种在美国、日本、欧洲的海水养殖中为常见的病原菌,但作为鱼类病原菌在中国属首次报道。

Abstract:

During the summer of 2006，an epizootic occurred among cultured tongue sole (Cynoglossus semilaevis Gunther) in a fish farm in Qingdao，China. The diseased tongue sole exhibited haemorrhaging of the basal fin，yellowed kidney and ulceration of the body surface. A Gram-negative，rod shaped bacterium (designated strain WY06) was isolated from the gall bladder of diseased fish. Pathogenicity assays revealed that WY06 was virulent to tongue sole and zebrafish (Danio rerio) by intraperitoneal injection challenge，with the LD₅₀ being calculated as 5.5×10³ cfu/g of fish (5.2×10⁵ cfu/fish) and 1.9×10³ cfu/g of fish (8.9×10² cfu/fish) respectively. The 16S rRNA gene sequence of strain WY06 demonstrated high similarity (99%) with Photobacterium damselae subsp. piscicida. Phylogenetic analysis showed a clear association of strain WY06 with P. damselae subsp. piscicida. Additional evidence of the identification included in morphological，physiological and biochemical data. The pathogen was sensitive to cifuroxime (３０μg) and ceftriaxone sodium (３０μg). Present study describes P. damselae subsp. piscicida from diseased fish for the first time in China.