草鱼致病性腐败希瓦氏菌的分离鉴定及药敏特性研究

Isolation, identification and antibiotic sensitivity of the pathogenic Shewanella putrefaciens from the grass carp Ctenopharyngodon idellus

从患病草鱼(Ctenopharyngodonidellus)体内分离获得1株革兰氏阴性细菌,菌株编号为C0703,通过细菌形态学观察、理化特性、16S rDNA序列分析以及构建系统发育进化树分析等进行鉴定研究。结果表明,该分离菌株氧化酶、七叶苷、硝酸盐还原等为阳性,赖氨酸脱羧酶、葡萄糖等为阴性;进一步采用PCR方法扩增16SrDNA序列测序获得片段大小1409bp,与模式菌株Shewanella putrefaciens ATCC 8071(NR 119141.1)序列相似性为98.23%;构建系统发育树分析显示与Shewanella putrefaciens(NR 119141.1)自然聚为一支,最终判定C0703菌株为腐败希瓦氏菌(S.putrefaciens)。人工回归感染草鱼试验显示,3d累积死亡率为100%,并与自然感染临床症状基本一致;药敏试验结果显示,菌株C0703对阿莫西林、美罗培南、萘啶酸等药物敏感,对氨苄西林、头孢唑啉、万古霉素等不敏感。本研究结果为鱼源腐败希瓦氏菌的诊断及防治等提供了科学参考。

A bacterial strain was isolated from the grass carp(Ctenopharyngodon idellus),and named C0703.The morphological observation,physiological and biochemical characteristics,sequencing of 16S rDNA and phylogenetic tree analysis were carried out in this study.Results showed that the C0703 strain was a rod-shaped,gram-negative bacillus;The isolated strain was positive for oxidase,esculin and nitrate reduction,and negative reaction for lysine decarboxylase and glucose etc.Furthermore,the 16S rDNA sequences were amplified by PCR method,to get fragment size of sequencing 1 409 bp.It had a 98.23%similarity with 16S rDNA sequence of Shewanella putrefaciens ATCC 8071(NR 119141.1),and clustered into one group with Shewanella putrefaciens(NR 119141.1),thus the C0703 strain was identified as Shewanella putrefaciens.Animal experiment showed that the isolated strain has pathogenic to grass carp and causeddeath with a 100%rate,which were consistent with the natural symptoms of diseased fishes.The antibiotic susceptibility testing showed that it was sensitive to amoxicillin,meropenem and nalidixic acid etc,but resistant to ampicillin,cefazolin and vancomycin etc.This study firstly reported the isolation and identification of Shewanella putrefaciens from grass carp,which will provide a scientific reference for prevention and treatment in fishes.