大鲵源迟缓爱德华菌的生物学特性及其感染的病理损伤

Biological Characteristics of Edwards tarda Isolated from A.davidianus and Resultant Pathological Lesions

【目的】研究引起两养殖场大鲵(Andrias davidianus)以肠炎、腹水为临床特征疫情的病原特性及其病理损伤特点。【方法】对患病大鲵进行细菌分离、形态学观察、生理生化测定、16S rDNA序列分析及毒力相关基因检测,并通过K-B法进行药敏试验和HE染色进行组织病理学观察。【结果】分别从患病大鲵的肝、肾和腹水中分离到两株优势菌(XY01,XY02),鉴定为迟缓爱德华菌(Edwards tarda),其携带citC、fimA、gadB、katB、mukF与esrB 6种毒力基因,对阿莫西林、万古霉素及卡那霉素等耐药,对氟苯尼考、庆大霉素和多黏菌素-B等敏感。组织病理学上,感染大鲵表现为多组织器官损伤和全身性炎症反应,尤其以肝、脾、肾和肠的病理损伤较为明显,表现为细胞变性、坏死,大量淋巴细胞、巨噬细胞和中性粒细胞浸润。【结论】明确了引起两养殖场疫情病原迟缓爱德华菌的生物学特性及其感染的病理学特点,为大鲵迟缓爱德华菌感染的诊断与防治提供了参考。

【Objective】To clarify the pathogenic characteristics and pathological lesions of Andrias da⁃vidianus with enteritis and ascites of two farms.【Method】Bacterial isolation,morphological observa⁃tion,biochemical determination,16S rDNA sequence analysis,drug sensitivity test by K-B,virulence-related genes detection and histopathological observation after HE staining have been performed on dis⁃eased A.davidianus.【Result】Two dominant bacterial strains(XY01,XY02)were isolated from the liver,kidney,and ascites of the diseased A.davidianus,which were identified as Edwards tarda with six virulence genes(citC,fimA,gadB,katB,mukF,esrB).The drug susceptibility results showed that the isolates were resistant to amoxicillin,vancomycin and kanamycin,but were sensitive to florfenicol,gen⁃tamicin and polymyxin-B.Histopathologically,the infected A.davidianus showed systemic inflammatory reaction and multiple tissues and organs were damaged,especially for liver,spleen,kidney and intes⁃tine,which manifested as cell degeneration and necrosis,and infiltration of a large number of lympho⁃cytes,macrophages and neutrophils.【Conclusion】The biological characteristics and the pathological characteristics were identified of E.tarda caused the disease in two farms,which provides reference for the diagnosis,prevention and treatment of E.tarda in A.davidianus.