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【目的】2012年7月,北京市怀柔区一家养殖场的杂交鲟爆发疾病,陆续死鱼。为确定病原,【方法】从具有典型症状的患病鱼的肝、肾和脾中分离获得3株分离菌,编号HRS12718L、HRS12718K和HRS12718S。采用形态特征、理化特性、16S rDNA和海豚链球菌特异性基因逐步鉴定病原菌的种类。取HRS12718K分离株进行人工感染实验,确认病原菌的致病性。开展药物敏感性实验筛选分离株的敏感药物。【结果】结果显示3株分离菌的形态特征和理化特性与从中国其它鱼类分离的海豚链球菌一致。采用16S rDNA序列构建的进化树与海豚链球菌聚为一支,与海豚链球菌的同源性在99.1%以上。HRS12718K分离株对杂交鲟的半致死量LD50为4.42×105CFU/mL,试验感染鱼出现与自然发病鱼相似临床症状。分离株对诺氟沙星、嗯诺沙星、硫酸新霉素、盐酸多西环素和盐酸四环素敏感,尤其对嗯诺沙星敏感。【结论】最终确认引起该养殖场杂交鲟发病的病原为海豚链球菌,建议使用嗯诺沙星进行治疗。
【Objective】 In July 2012, a hybrid sturgeon in a farm in Huairou District of Beijing broke out and died one after another. To determine the pathogen, [Method] Three isolates, HRS12718L, HRS12718K and HRS12718S, were isolated from liver, kidney and spleen of diseased fish with typical symptoms. Morphological characteristics, physicochemical properties, 16S rDNA and Streptococcus puccinique specific genes were used to identify the pathogen species. Take HRS12718K isolates artificial infection experiments to confirm the pathogenicity of pathogens. To carry out drug susceptibility testing of screening sensitive isolates. 【Result】 The results showed that the morphological and physicochemical properties of the three isolates were consistent with those isolated from other Chinese fish. The phylogenetic tree constructed by 16S rDNA sequence was integrated with Streptococcus agluciu and shared 99.1% homology with Streptococcus. LD50 of HRS12718K isolate was 4.42 × 105 CFU / mL for hybrid sturgeon. The clinical symptoms of infected fish appeared to be similar to that of naturally occurring fish. The isolates were sensitive to norfloxacin, carbenoxacin, neomycin sulfate, doxycycline hyclate and tetracycline hydrochloride, especially to nosinoxacin. [Conclusion] The pathogen that caused the sturgeon of hybrid sturgeon was finally identified as Streptococcus viridans. It is recommended to use carbenoxacin for treatment.