一株虹鳟源维氏气单胞菌的分离鉴定及组织病理学观察

Isolation and identification of Aeromonas veronii from rainbow trout and Histopathology Study of the Diseased Fish

为鉴定一起虹鳟突发疾病死亡的病原，本研究从自然发病虹鳟的内脏分离到一株致病菌WX153415，并对其进行了常规理化特性、分子生物学、人工感染试验和病理学观察以及药敏性检测。结果显示：分离株WX153415为革兰氏阴性短杆菌，其理化特性与维氏气单胞菌（A．veronii）特征相符，并且其16SrDNA基因、gyrB基因、毒力基因act、毒力基因aer和毒力基因aha序列与GenBank中A．vemnii的同源性均可达98％以上，在系统进化树中与A．veronii聚为一族；动物回归试验结果表明，分离株LD50为1．5×10^6cfu／mL；病理学观察显示该分离株主要损伤虹鳟的鳃、肝和肾等重要器官组织，综合检测结果表明该分离株为致病性A．veronii。药敏试验结果显示，分离株对14种抗菌药物中头孢哌酮、哌拉西林、氟苯尼考和头孢呋辛药物敏感。

In order to identify the agent of a serious disease occurred in rainbow trout, a dominant bacteria was isolated from the organ tissue of natural infected rainbow trout. And the isolate was further tested by physiological and biochemical assay, DNA sequence analysis, artificial infection; histopathology analysis and drug susceptibility test. The results showed that the isolate was a Gram-negative bacterium and physiological and biochemical characteristics were consistent with Aeromonas veronii. The sequences similarity analysis of 16S rDNA, gyrB and virulence genes （act, aer and aha） with A.veronii by Blast were up to 98%, and the isolate formed a cluster with other A. veronii reference strains by phylogenetic tree. Animal artificial infection with the isolate shows the isolate was pathogenic to the rainbow trout With LD50 of 1.5 ×10^6 cfu/mL, and the pathogenicity was also confirmed by pathological and histopathological examinationits. Overall, the isolate strain is proved to be a pathogenic A.veronii. The drug sensitivity results showed that among 14 antibiotics test the isolate was sensitive to cefoperazone, piperacillin, florfenicol and cefuroxime.