卵形鲳鲹美人鱼发光杆菌杀鱼亚种的分离鉴定

Isolation of Photobacterium damselae subsp.piscicida from diseased golden pompano(Trachinotus ovatus Linnaeus) and its drug sensitivity

2006年海南省凌水网箱养殖卵形鲳鲹(Trachinotus ovatus)出现大批死亡。肉眼观察病鱼体表完好,部分病鱼内脏稍肿大,病理组织研究显示脾脏和肝脏有灰白色结节。从病鱼的脾脏分离到1株明显优势菌,命名为TOS1,人工感染确认TOS1对卵形鲳鲹有强致病性,其半数致死量为1.1×106CFU/g,组织病理研究显示相同症状,因此确定TOS1为本次流行病的病原菌。经API鉴定系统和16SrDNA序列分析结合常规生化指标,将TOS1鉴定为美人鱼发光杆菌杀鱼亚种(Photobacterium damselae subsp.piscicida)。该菌具有很强的溶血性和较强的蛋白酶活性,对多种抗生素和中草药均具抗性,仅对诺氟沙星、环丙沙星、氯霉素、庆大霉素等敏感,对中草药番石榴(Psidium guajava)和苍术(Atractylodes lancea)高度敏感。以上敏感药物可作为该病预防或治疗的参考用药。

An epizooty occurred among cultured golden pompano（Trachinotus ovatus）with high mortality in Linshui of Hainan province,China in 2006.Diseased fish exhibited no obvious symptom,though pathological observation showed gray nodules scattered in spleen and kidney.A Gram-negative bacterium（designated strain TOS1）was isolated from its spleen.Pathogenicity assays revealed that TOS1 was virulent to golden pompano when it was challenged by intraperitoneal injection and the LD50 was 1.1×10^6CFU/g.The 16S rRNA sequence of TOS1 demonstrated high similarity（99%）with Photobacteriumdamselae subsp.piscicida.Phylogenetic analysis results also indicated close genetic relationship between strain TOS1 and P.damselae subsp.piscicida.Additionally,morphological,physiological and biochemical results verified the identification result.The pathogen had strong hemolytic and protease activity and was sensitive to norfloxacin（10μg/tablet）,profloxacin（5μg/tablet）,gentamicin（10μg/tablet）,sulfamethoxazole/trimethoprium（1.25/23.75μg/tablet）,neomycin（30μg/tablet）,streptomycin（10μg/tablet）,chloramphenico（30μg/tablet）and tetracycline（30μg/tablet）,and very sensitive to two Chinese herbal medicincs of psidium guajava and atractylodes lancea（MBC=10^-6g/mL）.