Abstract: In order to identify the pathogens causing mink pneumonia,a suspected strain of Klebsiella pneumoniae was isolated from clinical death cases.The nuclease activity of extracellular protein of Klebsiella pneumoniae was detected by agarose gel electrophoresis, and the effects of temperature, pH value and metal ions on the activity of nuclease were investigated. The results showed that Klebsiella pneumoniae was identified by microscopic examination and PCR.The exocrine protein of Klebsiella pneumoniae showed the activity of nuclease for degradation of λDNA.The optimal temperature range was 30—37 ℃ ,and the optimum pH value was 7.0.The activity of nuclease was weak under high temperature and alkaline conditions.Univalent metal ions (Na⁺and K⁺) and some divalent metal ions (Ca²⁺,Ba²⁺,Ni²⁺,Zn²⁺and Cu²⁺) had no significant effect on the nuclease activity of extracellular secretory protein of Klebsiella pneumoniae.The 5.00—10.00 mmol/L Co²⁺and Fe³⁺and 10. 00 mmol/L Mg²⁺and Mn²⁺could promote the activity of extracellular nuclease cleavaging λDNA.In this study,a Klebsiella pneumoniae strain was isolated from clinical mink pneumonia,and its exocrine protein had nuclease activity.

Key words: Mink, Klebsiella pneumoniae, Isolation and identification, Extracellular secretory protein, Nuclease

摘要： 为确定引起水貂肺炎的病原菌，对从临床死亡病例中分离到的1株疑似肺炎克雷伯菌进行鉴定，采用琼脂糖凝胶电泳法检测肺炎克雷伯菌胞外分泌蛋白的核酸酶活性，并探究了温度、pH值、金属离子对核酸酶活性的影响。结果显示，通过病料涂片镜检及PCR鉴定，分离株为1株肺炎克雷伯菌，该肺炎克雷伯菌胞外分泌蛋白表现出降解λDNA的核酸酶活性，最适温度为30~37 ℃，最适pH值为7.0，在高温和碱性条件的反应环境时核酸酶的活性较弱。一价金属离子（Na⁺、K⁺）和部分二价金属离子（Ca²⁺、Ba²⁺、Ni²⁺、Zn²⁺和Cu²⁺）对肺炎克雷伯菌胞外分泌蛋白的核酸酶活性无明显影响，而5.00～10.00 mmol/L的Co²⁺和Fe³⁺以及10.00 mmol/L的Mg²⁺和Mn²⁺可以促进胞外核酸酶切割λDNA的活性。综上，从临床水貂肺炎病例中分离到1株肺炎克雷伯菌，并证实该菌胞外分泌蛋白具有核酸酶活性。

关键词: 水貂, 肺炎克雷伯菌, 分离鉴定, 胞外分泌蛋白, 核酸酶