杂交鲟海豚链球菌的分离、鉴定及药物敏感性

Isolation，identification and drug sensitivity of Streptococcus iniae from hybrid sturgeons (Huso dauricus female×Acipenser schrencki male)

摘要:

摘要:【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4.42×105 CFU/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。

Abstract:

Abstract:［Objective］Sturgeons were the important economic species in Beijing．In July 2012，continuous mortality of cultured hybrid sturgeons was occurred on a farm in Huairou．［Methods］We isolated three pathogens from liver，kidney and spleen of the dying sturgeons with clinical symptoms，marked HRS12718L， HRS12718K and HRS12718S respectively．Then we analyzed theirs morphological，physiological and biochemical characteristics，and drug sensitivity．We also cloned and partially sequenced the 16S rDNA of strain HRS12718K． Moreover，we identified the pathogenic characteristic of strain HRS12718K by artificial infection．［Results］The morphological，physiological and biochemical characteristics of three strains were consistent with that of Streptococcus iniae isolated from other fishes in China，and 16S rDNA sequence of the strain HRS12718K was more than 99.1% homology with that of Streptococcus iniae．The LD50 of the pathogen to hybrid sturgeon was 4.42×105 CFU/mL，and challenged sturgeons presented the similar signs as the natural infected sturgeons． In addition，the bacterium was sensitive to norfloxacin，enrofloxacin，neomycin sulfate，doxycyline hyclate and tetracycline hydrochloride，and was highly sensitive to enrofloxacin． ［Conclusion］Streptococcus iniae was the pathogen to cultured hybrid sturgeons in Beijing area，and enrofloxacin can be used against the disease．