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从患暴发性流行病的西伯利亚鲟(Acipenser baerii)肝脏和心脏中各分离到1株细菌,分离纯化后获得2个分离株,编号分别为AeBF070904、AbHT070912,对分离菌进行了菌株鉴定、致病性分析及药敏实验。分别应用常规生理生化鉴定、全自动细菌测定卡API20STREP和ID32STREP进行检测,结果表明,2个分离株均为停乳链球菌(Streptococcus dysgalactiae)。对2个分离株的16S rRNA基因进行PCR扩增和测序,并与GenBank中收录的链球菌16S rRNA基因进行序列分析并构建系统进化树,结果显示,2个分离株的16S rRNA基因序列相同,与停乳链球菌同源性最高达97.3%,在系统进化树上与停乳链球菌聚为一簇,进一步确认2个分离株均为停乳链球菌。从人工感染后发病鱼的内脏组织再分离的细菌特性与原感染菌相同,确认停乳链球菌是西伯利亚鲟的致病菌。2个分离株对西伯利亚鲟、杂交鲟及剑尾鱼均有致死毒性,37℃培养的细菌毒力比28℃培养的细菌毒力强。2个分离株均对青霉素、诺氟沙星等7种药物敏感;对头孢唑啉、庆大霉素等2种药物耐受;对红霉素中等敏感;对卡那霉素等8种药物菌株之间出现差异。
One strain of bacteria was isolated from the liver and heart of Acipenser baerii with epidemic disease. Two isolates were obtained after isolation and purification. The isolates were identified as AeBF070904 and AbHT070912 respectively. The isolates were identified and pathogenic Sex analysis and susceptibility testing. The results showed that the two isolates were all Streptococcus dysgalactiae by using routine physiological and biochemical identification, API 20STREP and ID32STREP. The 16S rRNA gene of two isolates were amplified by PCR and sequenced. The 16S rRNA gene of Streptococcus was sequenced and the phylogenetic tree was constructed. The results showed that the 16S rRNA gene sequences of the two isolates were the same, Streptococcus dysgalactiae with homology of up to 97.3%, in the phylogenetic tree and Streptococcus dysgalactiae clustered together, further confirmed that the two isolates Streptococcus dysgalactiae. The bacterial characteristics isolated from the visceral tissues of diseased fish after artificial infection were the same as those of the original ones, and Streptococcus dysgalactiae was confirmed to be the pathogen of Siberian sturgeon. The two isolates had lethal toxicity to Siberian sturgeon, hybrid sturgeon and swordtail fish. The bacterial virulence at 37 ℃ was stronger than that at 28 ℃. The two isolates were sensitive to 7 drugs such as penicillin and norfloxacin, 2 kinds of drugs such as cefazolin and gentamicin, medium sensitive to erythromycin, 8 kinds of drugs such as kanamycin Differences between strains.