乌鳢烂身病病原的分离鉴定及病理组织观察

Isolation and identification of bacterial pathogen and histopathological change in skin ulcer disease of Chinese snakehead Channa argus

为探究乌鳢Channa argus烂身病的病因及患病乌鳢的体表组织病理学变化,从广东中山某养殖场患烂身病乌鳢病灶处分离到一株优势菌ZS20200317,通过形态学特征、革兰氏染色、16S rRNA及生理生化特性对分离菌株进行鉴定,并检测了该菌株的药物敏感性,最后采用回归感染试验确认分离菌株为导致乌鳢烂身病的病原菌。结果表明:患病乌鳢烂身处的肌肉组织出现了明显变性、坏死和炎症细胞浸润;LB琼脂培养平板培养结果显示,该菌呈边缘光滑有光泽的圆形白色菌落,为革兰氏阴性菌;16S rRNA基因进化分析显示,菌株ZS20200317与维氏气单胞菌Aeromonas veronii的亲缘关系最近,一致性高达98.5%;生理生化试验显示,该菌的赖氨酸脱羧酶、甘露醇、覃糖、蔗糖、氧化酶和VP等生理生化反应为阳性;药敏试验显示,该菌对氯霉素、头孢他啶、头孢氨苄、头孢唑林和头孢拉定沙星等20种抗生素药物敏感,对氨苄西林、苯唑西林、羧苄西林、青霉素G、麦迪霉素、万古霉素和克林霉素7种药物具有耐药性;人工回归感染试验证实,该菌能引起健康乌鳢死亡。研究表明,维氏气单胞菌是广东中山地区乌鳢烂身病的病原,本研究结果为乌鳢维氏气单胞菌病的防控提供了理论依据。

In order to explore the etiology and histopathological changes in skin ulcer disease of Chinese snakehead Channa argus,a dominant bacterial strain(designated as ZS20200317)was isolated from the diseased Chinese snakehead collected from Zhongshan,and identified through the analysis of morphological characters,Gram staining,16S rRNA gene,physiological and biochemical characters.The health Chinese snakehead was challenged with the isolated bacterium ZS20200317 for the confirmation whether the isolated bacterium was the causative bacterium for the diseased fish,and then sensitivity of the isolated bacterial strain ZS20200317 to 30 types of antibiotics was also tested.The results showed that the ZS20200317 was a Gram-negative bacterium with white colony of smooth edge and luster when cultured on the LB agar plate.The phylogenetic analysis of 16S rRNA indicated that ZS20200317 had the closest relationship with Aeromonas veronii,shared 98.5%similarities.Sensitive test of the bacterium showed that the strain had highly sensitive to 20 kinds of antibiotics,including chloramphenicol,ceftazidime,cefalexin,cefazolin and cefradine floxacin,had strong effects on the bacterium,and resistant to 7 kinds of drugs,such as ampicillin,oxacillin,carboxybenzillin,penicillin G,Medicin,vancomycin and clindamycin.Artificial regression infection showed that the bacterial strain led to the death of Chinese snakehead.The findings indicated that A.veronii was the pathogen of skin ulcer of Chinese snakehead in Guangdong Province,which will provide some reference basis for the prevention and control of disease induced by A.veronii in Chinese snakehead culture.