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2013年8—9月,四川雅安汉源湖养殖的西伯利亚鲟发生一种以体表溃疡、内脏出血和心外膜囊肿为特征的传染病。为明确其病因,本研究从自然发病鱼的肝、脾和肾进行了病原菌的分离、人工感染、分离菌的表型特征和分子生物学特征的检测。结果从患病鱼体内分离到一株G+链状球菌(Ab130920),人工感染实验证实了其病原性,生理生化特性与海豚链球菌(ATCC29178)基本一致;16S r DNA序列(Gen Bank登录号:KJ162337)与Gen Bank中S.iniae16S r DNA序列同源性最高,在以16S r DNA序列及其Gen Bank中同源性较高的相关序列构建的系统发育树上,分离菌与海豚链球菌聚为一支;同时,在基于S.iniae lct O基因的特异性PCR检测中,从分离株基因组DNA扩增出预期大小的870 bp条带,进而鉴定分离菌Ab130920为S.iniae。在对cps D、sim A、sag A、pdi和scp I等5种S.iniae毒力基因的多重PCR检测中,分离菌均扩增出相应大小的特异性片段,表明其为一毒力较强的菌株,与人工感染实验的高致病性结果相佐证;药物敏感性检测发现其对阿莫西林、强力霉素、氟苯尼考等抗菌药物敏感,但对新生霉素、利福平、氧氟沙星耐药。
From August to September 2013, Siberian sturgeon cultured at Hanyuan Lake, Yaan, Sichuan, developed an infectious disease characterized by body surface ulcers, visceral hemorrhage and epicardial cysts. In order to clarify its etiology, this study isolated the pathogenic bacteria, artificial infection, the phenotypic characteristics and molecular biological characteristics of the liver, spleen and kidney of naturally occurring fish. Results A strain of G + Streptococcus (Ab130920) was isolated from the diseased fish. The pathogenicity was confirmed by artificial infection. The physiological and biochemical characteristics of Streptococcus mutans (ATCC29178) were similar. The 16S rDNA sequence (Gen Bank Accession Number: KJ162337) had the highest homology with S.iniae16S r DNA sequence in GenBank. On the phylogenetic tree constructed with 16S r DNA sequence and related sequences with high homology in GenBank, At the same time, in the specific PCR detection based on S.iniae lct O gene, the expected size of 870 bp band was amplified from the genomic DNA of the isolates, and then the isolates Ab130920 was identified as S.iniae. In the multiplex PCR detection of five S.iniae virulence genes, such as cps D, sim A, sag A, pdi and scp I, specific fragments were amplified from the isolates, indicating that they were virulent Strong strains, and artificial infection test of the highly pathogenic results of phase evidence; drug sensitivity test found that amoxicillin, doxycycline, florfenicol and other antimicrobial drugs sensitive, but novobiocin, rifampicin Ofloxacin resistant.