A research of the epidemiology of enterohaemorragic E.coli O157 in wild rodents

为了解肠出血性大肠埃希氏菌的流行病学，采集了野生啮齿动物、河水和土壤。从山区捕获的211只野生啮齿类动物中分离到3只(1.4%)产维罗毒素的大肠埃希氏菌，在相关家畜场所捕获的62只野生啮齿动物中分离到1只(1.6%)产生维罗毒素的大肠杆菌。O157型大肠杆菌是从野生啮齿动物体内分离到的一种典型的肠出血性大肠杆菌(EHEC)血清型，经鉴定为非致病性大肠杆菌。用毒素检测试剂盒和聚合酶链式反应鉴定了4株病原菌产生Vero毒素1(VT1)，但O型不能产生VT1毒素。而且，我研究了一种从土壤和河水样本中分离EHEC的有效方法，但无法将EHEC从这些环境因素中分离出来。同时将EHEC接种到几种土壤中，检测不同温度下EHEC在这些土壤中的存活期。肠出血性大肠杆菌在37℃条件下消退较早，接种后3个月几乎检测不到细菌。但是，在23℃时，土壤中的细菌数量保持在相当大的数量。然而，在大约一个月的时间里，土壤中保持了较高的数量，而不受温度条件的影响。有人认为，感染牛的EHEC粪便落在地上，地面土壤受到EHEC的污染，污染将持续几个月。此外，我还检测了252份野生啮齿动物血清中的Vero毒素抗体。3个样本仅与VT1反应，4个样本与VT1和VT2反应。但目前还没有仅对VT2起反应的样本。共检出Vero毒素抗体7份(2.8%)。血清稀释度为80倍时，有5例(2.0%)对O157呈O型凝集。本研究未从野生啮齿动物体内分离到EHEC O157：H7，但提示野生啮齿动物体内存在EHEC O157的可能性较大。

To survey the epidemiology of enterohaemorragic Escherichia coli, (E.coli) wild rodents, river water and soils were collected. Verotoxin producing E.coli were isolated from 3 of 211 wild rodents (1.4%) captured in a mountainous area and 1 of 62 (1.6%) in the place of relating domestic animals. Serotype O157 E.coli, which was typical enterohaemorragic E.coli (EHEC) serotype, was isolated form wild rodents, but it was decided as non-pathogenic E.coli. Four pathogenic isolates were identified the production of Vero toxin 1 (VT1) by the toxin detection kit and PCR, but it could not be done in O-serotype. And, I examine an effective method to isolate EHEC from a sample of soil and river water, but it was not possible to isolate EHEC from these environment factors. While EHEC were experimentally inoculated into some kinds of soils and examined the existence period in these soils at different temperature. Extinction of EHEC was early in a condition of 37℃ and it became hardly to detect the organisms at 3 months after inoculation. But, at 23℃ the number of bacteria is kept the considerable amounts in soils. However a high number was maintained in the soil during approximately 1 month independently of temperature condition. It was suggested that the feces from EHEC infecting cattle fall to the ground, the ground soil is polluted by EHEC and that pollution will be continued between several months. Furthermore, I examined to detect the Vero toxin antibody at 252 serum samples from wild rodents. Three samples were reacted to VT 1 only and 4 samples were reacted to VT1 and VT2. But there is no sample to react to VT2 only. Total at 7 samples (2.8%) the antibody to Vero toxin was detected. And, 5 samples (2.0%) showed O-agglutination to O157 at the serum dilution 80 times. In this study, EHEC O 157 : H7 was not isolated from wild rodents, but it suggested that there is high possibility of possession of EHEC O157 at wild rodents.