黄颡鱼迟钝爱德华菌的分离鉴定及其致病性研究

为了确定黄颡鱼发病的原因，试验从患病黄颡鱼体内分离得到1株病原菌，命名为GDYM20160809，通过形态学观察、生理生化特性鉴定、16S rDNA分析及系统进化树构建等方法对分离菌进行鉴定，采用滤纸片扩散法对分离菌进行药敏试验。结果显示，该分离菌为革兰氏阴性短杆菌，PCR扩增其16S rDNA片段，经测序及BLAST比对，显示其与迟钝爱德华菌（Edwardsiella tarda）的同源性达100%，结合生理生化鉴定结果确定分离菌为迟钝爱德华菌。药敏试验结果显示，分离菌对磺胺类药物、头孢类药物、青霉素、复方新诺明等药物敏感，对磺胺间甲氧嘧啶钠、新生霉素、多黏菌素B、阿米卡星、卡那霉素和万古霉素6种药物耐药；人工感染试验结果证实，菌株对罗非鱼、禾花鲤、草鱼和黄颡鱼都有很强的致病性。本试验结果为有效防控黄颡鱼细菌性疾病提供了理论依据，并可指导养殖户合理用药。

Isolation and Identification of Edwardsiella tarda in Pelteobagrus fulvidraco and Analysis of Its Pathogenicity

For determining aetiological agent of Pelteobagrus fulvidraco,the pathogen was isolated from the diseased Pelteobagrus fulvidraco and named as GDYM20160809.The isolate was identified by morphological observation,physiological and biochemical characteristics,16S rDNA analysis and phylogenetic tree construction.The susceptibility test of the isolate was carried out by filter paper diffusion method.The results showed that the isolate was gram-negative bacillus and the 16S rDNA fragment was amplified by PCR.The 16S rDNA fragment was sequenced and compared by BLAST,the isolate was 100% homologous to Edwardsiella tarda.Combined with the results of physiological and biochemical identification,the isolate was determined as Edwardsiella tarda.Susceptibility test results showed that the isolate was sensitive to sulfonamides,cephalosporins,penicillins and cotrimoxazole and so on,and was resistant to sodium sulfasalazine,novobiocin,polymyxin B,amikacin,kanamycin and vancomycin six kinds of drugs.The artificial infection test results confirmed that the isolate strain had strong pathogenicity to tilapia,Procypris merus,grass carp and Pelteobagrus fulvidraco.The study provided a theoretical basis for the effective prevention and control of catfish bacterial diseases,and could guide farmers to rational drug use.