半滑舌鳎致病性荧光假单胞菌的分离鉴定及其感染的病理损伤

Isolation,identification and pathogenicity of pathogenic Pseudomonas fluorescens from Cynoglossus semilaevis Gunther

2015年6月,河北省秦皇岛市某养殖场半滑舌鳎发生以腹水、烂尾、内脏器官肿大、出血与坏死为特征的疾病。从自然发病的半滑舌鳎肝脏与肾脏中分离到1株细菌,通过细菌形态观察、培养特性、生化特性分析、动物试验和16SrRNA基因序列分析等方法,对该病原菌进行了分析鉴定。结果显示:致病菌株为革兰阴性杆菌,培养特性、生化特性分析与荧光假单胞菌较接近,以16SrRNA基因为遗传标记构建系统发育树,致病菌菌株与荧光假单胞菌菌株相似性为99%。结果表明:本次引起半滑舌鳎腹水烂尾病的病原菌为荧光假单胞菌。对分离到的菌株进行了常用抗药物的药敏试验,该菌对氧氟沙星、氨曲南、红霉素等药物高度敏感,对利福平、妥布霉素等药物中度敏感,对卡那霉素、新霉素不敏感。组织病理学观察发现,荧光假单胞菌感染半滑舌鳎对多个组织器官都造成明显的病理损伤,尤其是肝脏、肾脏、脾脏、肠及脑的损伤较为严重,表现为明显的淤血、出血,变性、坏死及炎症细胞浸润。

In June 2015,a disease characterized by ascites,tail ulcers rot,and tumefaction,bleeding and necrosis of visceral organ occured in a Cynoglossus semilaevis Gunther farm in Qinhuangdao,Hebei province.One bacterial strain was isolated from the liver and kidney of sick Cynoglossus semilaevis Gunther.The strain was identified on the basis of morphology,cultural performances,biochemical characteristics,animal test and 16 SrRNA sequence.The results showed that the stain was gram-negative bacterium and Its physiological and biochemical characteristics were samiliar to Pseudomonas fluorescence.In the phylogenetic trees,the sequence homology of the isolated strain and Pseudomonas fluorescens was 99% by constructing 16 SrRNA gene phylogenetic tree.So Pseudomonas fluorescens may caused the disease of Cynoglossus semilaevis Gunther tail ulcers rot.The pathogen was hypersensitive to ofloxacin,aztreonam,erythromycin;mediumsensitivity to rifampicin,tobramycin;and insensitive to kanamycin and neomycin.Histopathological observation found that Pseudomonas bacteriacaused obvious pathological injury of multiple tissues and organs especially more serious in the liver,kidney,spleen,intestine and brain with obvious congestion,hemorrhage,degeneration,necrosis and inflammatory cell infiltration.