鲶源维氏气单胞菌的分离鉴定及药敏特性

摘要

A bacterial strain, called as strain SG-1, isolated from liver of diseased northern sheatfish Silurus solda-tovi was shaped-rod and gram-negative bacterium by Gram-staining and identified as Aeromonas veronii by mor-phological, physiological and biochemical characteristics as well as the 16S rDNA gene sequencing and phylogenet-ic tree analysis. The isolated strain was shown to be characterized by glucose gas production, positive oxidase, ni-trate reduction, negative ornithine decarboxylase and hydrogen sulfide. Further fragment size of 16S rDNA se-quence amplified by PCR was 1409 bp, and had 99. 86% similarity with Aeromonas veronii ATCC35624 type strain. Phylogenetic tree analysis revealed that the isolate was clustered with Aeromonas veronii. The northern sheat-fish and zebrafish Danio rerio chalenged with Aeromonas veronii had mortality rate of 100%, showing surface bleed-ing, anal swelling, and ascites. Susceptibility test showed that the isolate was sensitive to cefixime, cefoperazone, cefotaxime, norfloxacin, levofloxacin, enrofloxacin, and florfenicol, but resistant to amoxicillin, ampicillin, sul-fisoxazole, methoxy pyrimidine, and cotrimoxazole.%为探明发病怀头鲶Silurus soldatovi的病原及其生物学特征,从发病怀头鲶体内分离出1株革兰氏阴性细菌SG-1,通过细菌形态学观察、 理化特性、16S rDNA测序和构建系统发育进化树分析对其进行了鉴定.结果表明:分离菌SG-1菌株葡萄糖产气、 氧化酶、 硝酸盐还原为阳性,鸟氨酸脱羧酶、 硫化氢为阴性;进一步采用PCR方法扩增其16S rDNA序列,测序获得片段大小为1409 bp,与维氏气单胞菌Aero-monas veronii模式菌株ATCC35624序列相似性达99.86%;构建系统发育树分析显示,分离菌与维氏气单胞菌自然聚为一支,最终判定SG-1菌株为维氏气单胞菌;人工感染斑马鱼Danio rerio、 鲶S.soldatovi,其死亡率均达100%,病鱼呈现体表出血、 肛门红肿、 腹水等症状;药敏试验结果显示,该菌对头孢克肟、 头孢哌酮、 头孢噻肟、 诺氟沙星、 左氟沙星、 恩诺沙星、 氟苯尼考等药物敏感,对阿莫西林、 氨苄西林、 磺胺异恶唑、 甲氧嘧啶、 复方新诺明等耐药.本研究结果为了解维氏气单胞菌感染鲶的致病机理及其该病的预防治疗提供了科学参考.