鳜源致病性舒伯特气单胞菌的分离鉴定及药敏试验

Identification and susceptibility test of pathogenic Aeromonas schubertii isolated from Siniperca chuatsi

【背景】舒伯特气单胞菌(Aeromonas schubertii)广泛分布于淡、海水水体和底泥中,致病株已在我国养殖鳢科鱼类中流行,也感染其他经济鱼类,导致暴发性死亡。【目的】对病鳜(Siniperca chuatsi)的病原进行鉴定,确定分离菌的致病性及药物敏感性,为该病临床治疗提供参考。【方法】采集病鳜脾肾组织进行PCR或RT-PCR扩增其常见病毒,采集病鳜肝脏和腹水分离培养细菌,PCR扩增代表菌株的gyrB、16S rRNA和毒力基因,鉴定其生理生化特征,并进行药物敏感性试验和人工感染试验。【结果】病鳜的传染性脾肾坏死病毒、鳜蛙病毒、鳜弹状病毒检测结果为阴性,肝脏和腹水均存在大量细菌;代表菌株Gui210820被鉴定为舒伯特气单胞菌,携带溶血素、气溶素、弹性蛋白酶和磷脂酶毒力基因,腹腔注射感染鳜的半数致死浓度(LD50)为3.16×105 CFU/mL;菌株Gui210820对四环素、卡那霉素、复方新诺明等6种抗菌药物耐药,对强力霉素中介,对恩诺沙星、新霉素、氟苯尼考等11种抗菌药物敏感。【结论】本试验从病鳜组织分离到致病性舒伯特气单胞菌,水产准许用药物恩诺沙星、新霉素、氟苯尼考可以用于本次疾病的临床治疗。

[Background]Aeromonas schubertii is ubiquitous in fresh water,seawater,and sediment.The pathogenic strains have been prevalent in cultured Channidae fish in China and infected other economic fishes,leading to death outbreak.[Objective]The pathogen was isolated and identified from the diseased Siniperca chuatsi.The pathogenicity and drug sensitivity of the isolate were determined,thereby providing references for the clinical treatment of this disease.[Methods]The spleen and kidney tissues of the diseased S.chuatsi were collected for polymerase chain reaction(PCR)or real-time PCR(RT-PCR)amplification of common viruses.The liver and ascites of the diseased S.chuatsi were pooled for the bacterial isolation and cultivation.The gyrB,16S rRNA and virulence genes of the representative strain were amplified by PCR,and their physiological and biochemical characteristics were identified.The susceptibility test and the artificial infection test were carried out.[Results]The detection results of infection spleen and kidney necrosis virus,Siniperca chuatsi ranairidovirus and Siniperca chuatsi rhabdovirus in the diseased S.chuatsi were negative,but large amount bacteria were observed from the liver and ascites.The representative strain Gui210820 was confirmed as A.schubertii,and carried the virulence genes of hemolysin,aerolysin,elastase and lipase.The median lethal concentration(LD50)of S.chuatsi infected by peritoneal injection was 3.16×105 CFU/mL.The Gui210820 strain was resistant to 6 kinds of antibiotics such as tetracycline,kanamycin,and cotrimoxazole,and sensitive to 11 kinds of antibiotics,including doxycycline,enrofloxacin,neomycin,and florfenicol.[Conclusion]In this study,pathogenic A.schubertii has been isolated from the tissues of the diseased S.chuatsi.Aquatic approved drugs enrofloxacin,neomycin,and florfenicol can be used for the clinical treatment of this bacterial disease.