患腹水病牙鲆病原菌分离、鉴定及病原菌的特性

为确定引起河北北戴河地区养殖牙鲆患腹水病死亡的病原,本实验从患腹水病牙鲆体内分离到3株优势菌,对分离株进行生理生化鉴定和16S rRNA序列比对来确定分离株的生物学地位,进一步通过毒力基因(toxR、vhhA、vhhB)鉴定及组织病理学分析其病理特征,并通过人工回感实验分析分离株毒性。结果显示,通过生理生化实验及16S rRNA序列比对,确定此次从患病牙鲆中分离到的3株菌株均为哈维氏弧菌;经鉴定,3株分离株毒力基因(toxR、vhhA、vhhB)结果均为阳性,病理组织切片结果显示,该分离株对牙鲆多器官(肠、肾脏、脾脏和肝脏)均可造成不同程度的病理损伤,呈全身性感染;人工回感实验显示,菌株BDHYPFS-Y1G对牙鲆的半致死浓度为LD50=5.88×106 CFU/mL,低于自然状态毒性;药敏实验表明,3株分离株均对呋喃妥因高度敏感。本实验确认了此次牙鲆腹水病的病原菌,并初步研究了病原菌致病性以及药物敏感性,以期为牙鲆工厂化养殖疫病防控提供科学依据。

Isolation, identification and characteristics of pathogenic bacteria from Paralichthys olivaceus with ascites

In order to determine the pathogen, which can cause the death of cultured Paralichthys olivaceus from ascites disease in Beidaihe area, Hebei Province, three dominant bacteria were isolated from P. olivaceus infected with ascites. The biological status of the isolates was determined by physiological and biochemical identification and 16S rRNA sequence alignment. The pathological characteristics of the isolates were further identified by virulence genes (toxR, vhhA, vhhB) and histopathological analysis. The results showed that the three isolates were Vibrio harveyi and the virulence genes of the three isolates were all positive. Pathological sections showed that the isolates could be used to damage multiple organs (intestine, kidney, spleen and liver) of P. olivaceus. The LD₅₀ of strain BDHYPFS-Y1G to P. olivaceus was 5.88×10⁶ CFU/g, which was lower than the toxicity of natural state. Drug susceptibility test indicated that all three isolates were highly sensitive to the nitrofurantoin. This study confirmed the pathogen of this ascites disease, and preliminarily studied the pathogenicity and drug sensitivity of the pathogen, which can provide scientific basis for the prevention and control of the disease in industrial culture of flounder.