鲫腹水症病原菌分离鉴定及药敏试验

从河南新乡某养殖场患腹水症的鲫鱼体内分离纯化获得1株细菌,编号为CA1618,通过细菌形态学观察、Biolog微生物鉴定系统,进一步采用PCR方法扩增其16SrDNA序列分析。结果表明CA1618菌株为革兰阴性杆菌,利用葡萄糖、麦芽糖、半乳糖、海藻糖等多种碳源,与Aeromonas sobria特征同源性为0.575、遗传距离为6.226;测序获得16SrDNA序列片段为1 363bp,与Aeromonas sobria序列同源性为99%~100%,构建系统发育树表明与模式菌株Aeromonas sobria ATCC43979T(GenBank登录号:X74683)亲缘关系最近,最终鉴定为温和气单胞菌(Aeromonas sobria)。CA1618菌株人工感染鲫鱼半数致死量(LD50)为1.55×10~7 CFU/mL,药敏试验显示对头孢哌酮、头孢噻肟、头孢克肟、萘啶酸、诺氟沙星、复方新诺明、四环素、氯霉素等抗生素敏感。

Isolation,Identification and Antimicrobial Susceptibility Test of Pathogenic Aeromonas sobria from Ascitesosis of Crucian Carp

The bacterial strain was isolated from the diseased crucian carp (Carassius carassius) mainly occured the abdominal swelling and ascitesosis,which were collected from a fish farm in Xinxiang city,Henan province.The results showed that a purified bacterial strain was isolated from the liver and then named strain CA1618,it was identified as the Aeromonas sobria by using bacterial morphology,biochemical characteristics of Biolog GenⅢ microstation system,amplification of 16 S rDNA gene sequence based on PCR method and construction of phylogenetic tree analysis.The strain CA1618 was Gram-negative rod-shaped cells,showing fermentation of glucose,maltose,galactose and trehalose etc.,and similarity and distance of physiological and biochemical characteristics compared with Aeromonas sobria were 0.575 and 6.226,respectively.The 16 S rDNA gene sequence of the isolate CA1618 was 1 363 bp in length,and Blast alignments showed that the isolate shared the 99%-100% sequence identities of 16 S rDNA with the reference strain Aeromonas sobria.It had the closest relationship,and naturally clustered into one group with type strain Aeromonas sobria ATCC43979 (GenBank No.X74683) by phylogenetic tree analysis.The isolate CA1618 exhibited a 50% lethal dose (LD50) of 1.55×107 CFU/mL.Antimicrobial susceptibility pattern of the isolate showed it was susceptible to cefoperazone,cefotaxime,cefixime,nalidixic acid,norfloxacin,sulfamethoxazole/trimethoprim,tetracycline and chloromycetin,etc.