中文摘要：

为了从猪源大肠杆菌中获得纯度高、产率高的脂多糖（lipopolysaccharides,LPS）,并评价其毒力,本试验采集仔猪腹泻粪便作为病料,进行细菌分离鉴定和16SrDNA鉴定,采用热酚水法提取细菌的LPS,通过DNaseⅠ、RNaseA、蛋白酶K和醇沉法对LPS进行纯化,通过苯酚硫酸法、Bradford法和紫外分光光度法测定LPS多糖、蛋白及核酸含量,鲎试剂定量法测定其活性,采用小鼠急性毒性试验方法测定小鼠半数致死量（LD50）。结果显示,分离获得一株具有高致病性的猪源大肠杆菌,纯化的猪源大肠杆菌LPS平均产率为3.74%,其中多糖含量为13.40%,蛋白含量为0.48%,核酸含量为0.06%,主要条带集中在14～160ku范围内,鲎试剂定量法测定其活性为1.21×10^7 EU/mg,提取LPS对小鼠的LD50为31.86mg/kg。该猪场仔猪腹泻是由致病性大肠杆菌引起,获得其毒力因子LPS纯度高、产率高、毒力强,这将为临床防制猪大肠杆菌病及LPS提取纯化提供理论依据。

英文摘要：

In order to obtain higher purity and high yield of LPS isolated from Escherichia coli,and evaluate its virulence,excrement of diarrhea piglet was collected as pathological samples,of which,some strains of Escherichia coli were isolated and identified.And furthermore,a strain of Escherichia coli was acquired by 16 SrDNA identification.The LPS from this strain of Escherichia coli was isolated with the hot-phenol water method and purified by DNaseⅠ,RNaseA,proteinase K treatment and alcohol precipitation.The polysaccharide,protein and nucleic acid content of purified LPS were detected by phenol-sulfuric acid method,Bradford method and UV points spectrophotometric method.And its bioactivity and acute median lethal dose was determinated by tachypleus amebocyte lysate（TAL）method and acute toxicity experiment method,respectively.The results showed that a strain of highly pathogenic Escherichia coli was successfully isolated.The average yield of purified LPS was 3.74%,the proportion of the polysaccharide was 13.40%,the protein was 0.48%,and the nucleic acid was 0.06%.SDS-PAGE electrophoresis and silver stain showed that the bands were mainly concentrated in the range of 14 to 160ku.The LAL bioactivity of the prepared LPS was 1.21×10^7 EU/mg,LD50 of the mouse abdominal cavity was 31.86mg/kg.The results revealed that the diarrhea piglets in the farm was caused by pathogenic Escherichia coli,purified LPS from this strain of Escherichia coli had the advantagesof higher purity,high yield and strong virulence,which would provide theoretical data for clinical prevention and treatment of diarrhea piglets.