单核细胞增生性李斯特菌感染ICR小鼠模型的建立

Establishment of a ICR Mice Model Infected by Listeria monocytogenes

单核细胞增生性李斯特菌(Listeria monocytogenes,LM)是一种人畜共患食源性致病菌,能引起人和动物较为严重的感染症状。现广泛使用具有免疫活性的小鼠模型测定半数致死量(LD50)来评价不同LM菌株的致病性。为建立LM的ICR小鼠模型,本研究采用1/2a血清型的N21 LM菌株,分别以106、107、108、109和1010CFU的剂量口腔灌注感染6周龄ICR小鼠,每组10只;另取10只接种PBS作为对照组,测定LM对ICR小鼠的LD50;另取40只小鼠,平均分为2组,公母各半,以测定的LD50剂量接种LM,分别对各组小鼠临床症状、组织病理变化、体重变化及组织中细菌载量进行评价。结果发现,N21 LM菌株对ICR小鼠的LD50为109.25CFU;感染周期为10 d左右,感染小鼠出现被毛粗糙、精神萎靡、阴茎垂出及体重下降等临床症状。组织病理学分析结果显示,肝脏先后出现实质内灶状细菌团块、形成血栓、细胞坏死等;脾脏主要表现为白髓内淋巴细胞减少;肺脏主要表现为纤维素性肺炎。菌落计数和Real-time PCR的检测结果发现肝脏中细菌载量最高,脾脏次之。结果表明,ICR小鼠能作为单核细胞增生性李斯特菌的感染模型。本试验结果为研究LM的致病机制、疫苗研究及抗菌肽转基因小鼠抗LM的评价奠定了基础。

Listeria monocytogenes （LM） was a zoonotic foodborne pathogen that could cause severe symptoms of infection in human and animals.Measuring LD50 of mice models which had immune activities was widely used for evaluation of pathogenicity of LM strains. In order to create a ICR mice model infected by LM, the N21 LM strains of the 1/2a serotype were inoculated orally into 6-week-old ICR mice groups （each group containing 10 mice） with the dose of perfusion 106,107,108,109 and 1010 CFU per mouse, respectively, the other 10 mice were inoculated by PBS as a control group to measure LD50 of LM infecting ICR mice. Another 40 mice were divided into two groups by gender, and inoculated with the dose of calculated LD50 of LM.Clinical symptoms, changes of histopathological, changes of body weight and tissue bacterial load were evaluated in each group, respectively.The results found that the LD50 of N21 LM was 109.25 CFU. The cycle of infection was about 10 days, the infected mice showed the clinical symptoms of rough coat, listlessness, penis hanging out, weight loss,etc.The histopathology analysis suggested that liver had appeared bacterial clumps in parenchyma, thrombosis and necrosis in sequence; spleen mainly showed white intramedullary lymphopenia decreased;lung mainly showed fiber simply pneumonia. Colony counting and Real-time PCR found that the highest bacterial load was in the liver, spleen followed. The experimental results showed that the ICR mice could be utilized as a LM infection model. This study laid the foundation for research on LM pathogenic mechanisms, vaccine development and evaluation of antimicrobial peptides transgenic mouse＇s resistance to Listeria monocytogenes.