团头鲂致病性维氏气单胞菌的分离鉴定及耐药性分析

Isolation,identification and drug susceptibility of the pathogenic Aeromonas veronii from Megalobrama amblycephala

为鉴定长春市某水产养殖场团头鲂的病原菌,从患病团头鲂体内分离到致病菌JWC086,对其形态和生理生化特性进行了鉴定,并对16S r DNA和管家基因gyr B序列、毒力基因携带情况及耐药性进行了分析。结果显示,该菌为革兰阴性菌,其生理生化特性与维氏气单胞菌基本相同。16S r DNA序列比对结果表明,该菌与维氏气单胞菌(KP716691)的同源性在99%以上。基于16S r DNA与gyr B序列的进化分析显示,该菌与维氏气单胞菌同属一个分支,同源性较高。将分离菌人工感染团头鲂,7 d内团头鲂全部死亡,且临床症状与自然病例相似。通过毒力基因检测发现,能从JWC086扩增出气溶素(aer)、细胞毒性肠毒素(act)、黏附素(Aha)、丝氨酸蛋白酶(ser)、核酸酶(exu)、脂肪酶(lip)及密度感应系统调控基因(Lux S)等7种毒力因子。药敏试验结果显示,该菌对氟苯尼考及复方新诺明等药物比较敏感。本研究为团头鲂感染维氏气单胞菌的鉴定及治疗提供了科学依据。

To understand the cause of disease in the Megalobrama amblycephala farm,one pathogenic bacterium was isolated from the naturally infected M. amblycephala. It was identified as Aeromonas veronii by ana lyzing the colony morphology,physical and chemical characters and the sequences of 16 S r DNA and housekeeping gene gyr B,and named as JWC086. The results showed that characters of JWC086 were similar to A. veronii,and the sequence homology of 16 S r DNA between JWC086 and other A. veronii strains were high,accounting for99%. In addition,the evolutionary analysis based on 16 S r DNA and gyr B sequences indicated that JWC086 had closer phylogenetic relationship with A. veronii. And there were same symptoms between the artificially infected and naturally infected M. amblycephala.Total seven virulence genes were detected from JWC086,including aerolysin（aer）,cytolytic enterotoxin（act）,maior adhesin（Aha）,serine protease（ser）,extracelluar protease（exu）,lipase（lip） and Lux S genes.The results of drug susceptibility test showed that JWC086 was sensitive to florfenicol and sulfamethoxazole compound. These results provide a scientific basis for the identification and treatment of M. amblycephala infected with A. veronii.