禽大肠埃希氏菌融合菌株疫苗的研制及应用

对从陕西省主要养鸡地区病死鸡分离的禽致病性大肠埃希氏菌进行Omp分型 ,用不同Omp型的菌株构建成融合菌株。用融合菌株制作铝胶灭活疫苗 ,与单价疫苗和两亲本菌株双价疫苗的免疫保护效果进行比较。结果表明 ,融合菌株疫苗可对多种O血清型致病性大肠埃希氏菌的攻毒试验产生坚强的保护 ,保护率高达 93%～ 10 0 % ,而O血清型单价疫苗的保护率仅 6 7%～80 % ,双价疫苗的保护率仅 80 %。在生产中对蛋用鸡的应用结果表明 ,融合菌株疫苗可明显降低鸡的死淘率。     

新生仔猪大肠埃希氏菌性腹泻K88ac-ST1-LTB三价基因工程灭活疫苗生产工艺的研究

以实验室工艺为基础,用发酵罐培养,对培养基、诱导剂及诱导条件、通气量、菌液灭活条件等进行了筛选优化。结果表明,重组菌株BL21(DE3)(pXK88acST3LT5)培养的最适培养基为改良LB培养基;乳糖为适合于工业化生产的诱导剂,其最适浓度为100 mmol/L,诱导时间不低于6 h;2×105mL发酵罐培养的最佳通气量为500 L/min;培养菌液的灭活条件为按菌液总量加入4 mL/L甲醛溶液,37℃灭活48 h。按上述工业化生产条件生产疫苗5批,检验结果均安全有效。     

体外药动学模型中恩诺沙星对猪大肠杆菌的药效研究

为使畜禽专用的喹诺酮类药物更合理地应用,通过建立体外模型的方法,研究了恩诺沙星对大肠杆菌的药效。结果,在消除半衰期为3 h的模型内,2MIC(最小抑菌浓度)的恩诺沙星对猪大肠杆菌仅能抑制4 h,模型运行4 h后细菌出现再生长。5MIC和8MIC的恩诺沙星对猪大肠杆菌可抑制6 h,模型运行6 h后细菌出现再生长。16MIC的恩诺沙星可在模型运行期间对猪大肠杆菌产生持续的抑制杀灭作用。在消除半衰期为6.5 h的模型内,2MIC的恩诺沙星对猪大肠杆菌仅能抑制4 h,模型运行4 h后细菌出现再生长。5MIC、8MIC和16MIC的恩诺沙星可在模型运行期间对猪大肠杆菌产生持续的抑制杀灭作用,4 h已经不能检测到猪大肠杆菌的存在。结果表明,若要使恩诺沙星发挥持续的抗菌效果,保持Cmax/MIC大于一定数值,同时维持有足够高的AUC0→24/MIC是非常必要的。     

动物性食品中大肠埃希氏菌O157∶H7特异性二重PCR检测方法的建立

根据大肠埃希氏菌O157∶H7wzx和fliC基因的保守序列设计了2对引物,建立并优化了特异性检测大肠埃希氏菌O157∶H7的二重PCR体系,扩增产物为395bp(wzx)和1057bp(fliC)。人工培养基中大肠埃希氏菌O157∶H7的检测下限为2.3×102CFU/mL,人工污染的牛乳、猪肉及牛肉中大肠埃希氏菌O157∶H7的检测下限分别为5.8×102CFU/mL、4.3×102CFU/g和3.1×103CFU/g。样品经3h预增菌后检测下限可达3.1×100~5.8×100CFU/mL(或CFU/g)。试验结果提示,针对wzx及fliC基因的二重PCR方法可以快速特异地检测出牛乳、猪肉及牛肉中大肠埃希氏菌O157∶H7的污染。     

基于thyA基因的大肠杆菌染色体-质粒平衡致死系统的构建与应用

将大肠杆菌DH5α在含胸腺嘧啶核苷和三甲氧苄二氨嘧啶的琼脂平板上培养,获得了遗传稳定的ThyA-大肠杆菌DH5α21株。用PCR扩增野生菌和ThyA-大肠杆菌的thyA基因,将测定的序列与野生型thyA基因相比,6号突变株的thyA基因第92位碱基发生G→A转换,导致第31位甘氨酸被天冬氨酸替换,4、7和13号突变株的thyA基因从第73位连续缺失6个碱基,导致第25位甘氨酸和第26位苏氨酸缺失。经PCR扩增的包括启动子在内的鼠伤寒沙门菌thyA基因与野生型大肠杆菌DH5αthyA基因的同源性为86%。以鼠伤寒沙门菌thyA基因为选择标记,构建了含人溶菌酶基因的真核表达载体pDTALYZ,以ThyA-大肠杆菌为受体菌,构建了染色体-质粒平衡致死系统。在相同条件下,pDTALYZ转化ThyA-大肠杆菌的效率高于以卡那霉素抗性基因为选择标记的pcDNAKLYZ转化野生大肠杆菌的效率;在发酵培养过程中,两种重组菌的生长速率相似,质粒丢失率分别为25%和10%,湿菌重分别为57.68 g/L和51.00g/L,重组质粒产量分别为134.9 mg/L和135.0 mg/L。     

产志贺毒素Ⅱ型变异体大肠杆菌LAMP检测方法的建立

为建立产志贺毒素Ⅱ型变异体(Stx2e)大肠杆菌的环介导恒温扩增(LAMP)检测方法,参照Gen-Bank中12条Stx2e序列和9条Stx2序列,针对Stx2e基因保守区域设计并合成4条引物,分别进行了反应条件优化、特异性试验、敏感性试验及模拟样品检测。结果显示,用所建立的LAMP方法对阳性样品扩增所得产物电泳后呈特征性梯状条带,阴性样品的扩增产物电泳后均无扩增条带。建立的LAMP方法对Stx2e+大肠杆菌的最低检出量为38CFU/管,敏感性高于PCR方法(3.8×103CFU/管)。LAMP和PCR对模拟样品检测结果的符合率为100%。该研究为仔猪水肿病的诊断和Stx2e+大肠杆菌的快速检测提供了新的方法。     

Pathogen detection using a liquid array technology

Abstract: Low concentrations of microbial pathogens in pure and mixed samples were detected using a bead‐based, liquid array technology. A 20‐bp sequence in the 23S rRNA gene, rrl, was amplified in four microorganisms: Bacillus cereus, Escherichia coli, Salmonella enterica and Staphylococcus aureus. PCR products were positively identified with the Luminex^® 100? system. The system could detect very low amounts of DNA and the instrument response was proportional to the input concentration. The lower limit of detection (LLD) was determined to be 0.5 ng for B. cereus and E. coli and 2 ng for S. enterica. The LLD for S. aureus was not determined as the instrument response was still above the threshold when quantities of DNA as low as 0.25 ng were used. The platform positively identified organisms present in mixed samples even when the minor component was overshadowed by a 10‐fold excess of the major component.     

新疆羔羊腹泻中大肠埃希氏杆菌的研究

对新疆5个地区分离到的510株大肠埃希氏杆菌用126种O抗血清鉴定,定出O型57种。较集中的O型分别为O_(?)(26株),O_(101)(21株),O_(106)(19株),O_(93)(17株),O_(?)(16株),O_(?)(12株)。用K_(99)、F_(41)抗血清对9个地区的750株菌鉴定,定出K_(99)阳性菌31株,占4.1％;F_(41)阳性菌19,占2.5％。用羔羊肠环结扎和乳鼠灌胃方法测毒,仅K_(99)表达稳定的菌株呈阳性反应。用小白鼠测定不同地区、年份疫区分出的203株茵的毒力,致死率在41.3％～87.5％之间。把不同疫区分出的10株菌单独或混合接种初生羔7只,6只发病。用同一地区健康群分出的菌接 种小白鼠、回归羔羊,其毒力和致病性与疫群菌株基本相同。     

大肠杆菌O157∶H7胶体金免疫层析检测试纸条在感染牛和小鼠排菌检测中的应用

为了检验大肠杆菌O157∶H7胶体金免疫层析检测试纸条在感染动物排菌中的应用效果,将牛和小鼠采用灌胃攻毒方式试验感染大肠杆菌O157∶H7,用大肠杆菌O157∶H7胶体金免疫层析检测试纸条、细菌鉴别培养基培养计数以及PCR 3种方法检测感染动物粪便中O157∶H7的排菌量和持续时间。牛在感染大肠杆菌O157∶H7后的第2天开始从粪便排菌,第4天达到峰值,排菌时间可持续28d;小鼠在感染O157∶H7后的第4小时开始从粪便排菌,第6小时达到峰值,排菌时间可持续15d。大肠杆菌O157∶H7胶体金免疫层析检测试纸条、细菌鉴别培养基培养计数以及PCR 3种方法的检测结果一致,但试纸条更简便、快捷、直观,1～5min可得出检测结果,便于现场检测样品中O157∶H7的快速筛查。     

Septic Ketoacidosis—A Potentially Lethal Entity with Renal Tubular Epithelial Vacuolization

Fatal ketoacidosis due to diabetes mellitus, alcoholism, and starvation may produce characteristic basal vacuolization of renal tubular epithelial cells (RTEC). Septic ketoacidosis has recently been recognized clinically as a distinct condition in which septicemia can lead to elevation of ketones and various anions unrelated to diabetes mellitus, alcoholism, or caloric deprivation. We report four lethal cases with significantly elevated vitreous ketones secondary to sepsis and/or severe localized infection in individuals with no history of diabetes mellitus, alcoholism, or starvation. Three of four cases exhibited typical basal vacuolization of RTEC. We suggest that septic ketoacidosis is an appropriate cause of death in the forensic setting where sepsis or severe localized infection is found with significant ketoacidosis (β‐hydroxybutyrate > 5 mmol/L)—in the absence of diabetes mellitus, alcoholism, starvation, or other states associated with accelerated ketogenesis. The finding of basal vacuolization of RTEC in such cases provides morphological support for the underlying metabolic derangement.