致病性大肠杆菌和出血性大肠杆菌的研究进展

致病性大肠杆菌(EPEC)是导致婴幼儿腹泻的主要病原菌，特别在发展中国家。近期研究表明，EPEC病原与宿主细胞的作用可视为三个阶段。第一阶段，局限性的粘附在上皮细胞；第二阶段，产生分泌蛋白：第三个阶段，紧密粘附和受体蛋白的作用。一些出血性大肠杆菌侵袭人的肠上皮细胞也靠粘附和损伤作用。     

人乳头状瘤病毒16E7在人喉癌细胞系中的转染及表达

目的:构建含人乳头状瘤病毒16E7(HPV16E7)基因的真核表达载体,观察HPV16E7对人喉癌HEp-2细胞系生物学特性的影响,为后续实验提供研究对象.方法:以含HPV16E7基因的中间质粒pET28a-HPV16E7为模板扩增出HPV16E7基因全长序列,将其克隆到真核表达载体pcDNA3.1/myc-His(-) B中,并进行序列分析和酶切鉴定.电穿孔法将重组体pcDNA3.1/myc-His-HPV16E7转染入喉癌HEp-2细胞中,Western 印迹法检测HPV16E7蛋白的表达,相差显微镜观察转染前后的HEp-2细胞系形态学变化,流式细胞仪检测转染前后细胞生长周期的改变.结果:成功构建并将pcDNA3.1/myc-His-HPV16E7转染入人喉癌HEp-2细胞中;转染后HEp-2细胞增生活跃,S期明显延长,并能够稳定表达HPV16E7蛋白.结论:HPV16E7有促进HEp-2细胞的致瘤活性;真核表达载体pcDNA3.1/myc-His-HPV16E7可为下一步建立动物模型和喉癌体外治疗实验提供研究工具.     

基孔肯雅病毒包膜蛋白E2的全基因合成及原核表达

目的通过对全长基孔肯雅病毒包膜蛋白E2(CHIKV-E2,1～404 aa)及其跨膜疏水区(351～378 aa)缺失突变体E2(1～350 aa)进行原核表达,分析跨膜疏水区对E2蛋白在大肠杆菌中表达的影响。方法利用ExPasy预测软件对E2蛋白跨膜疏水区进行预测分析,根据GenBank数据库中CHIKV-E2氨基酸序列获得其对应的基因序列。结合重叠延伸PCR(OE-PCR)原理设计用于全基因合成的核酸引物对CHIKV-E2全长基因(404 aa)进行体外合成,构建全长E2蛋白及其缺失突变体原核表达质粒,将序列正确的两种重组质粒分别转至E.coli BL21(DE3),经IPTG诱导表达,SDS-PAGE检测重组质粒的表达情况。结果 OE-PCR法成功合成了大小为1 212 bp的编码CHIKV-E2(1～404 aa)蛋白的全长基因,构建了全长E2蛋白及其缺失突变体重组表达质粒pET21b-E2(1～404)和pET21b-E2(1～350),经IPTG诱导表达后,SDS-PAGE结果显示缺失突变体pET21b-E2(1～350)融合蛋白表达量较pET21b-E2(1～404)有明显提高。结论 E2蛋白跨膜疏水区(351～378 aa)对该蛋白的原核表达具有重要影响,缺失该疏水区的突变体在大肠杆菌中表达量比全长E2蛋白表达量明显提高。     

产毒性和致病性大肠杆菌中小肠结肠炎耶尔森菌强毒力岛的检测

目的　了解小肠结肠炎耶尔森菌强毒力岛在产毒性和致病性大肠杆菌中的分布,探讨毒力岛在大肠杆菌中的结构和功能。方法　对毒力岛的关键基因irp2、fyua和asn-intB进行PCR扩增和DNA测序,并对irp2和fyua进行原位杂交。结果　在检测的93株肠产毒性大肠杆菌和10株肠致病性大肠杆菌基因irp2的检出率分别为32.25％（30/93）和30％（3/10）,fyua的阳性率为21.51％（20/93）和30％（3/10）,而且这些阳性菌株中的毒力岛大部分连接到天门冬氨酸tRNA（asn tRNA）位点。结论　小肠结肠炎耶尔森菌强毒力岛在产毒性和致病性大肠杆菌中较高的阳性率,对于大肠杆菌毒力的变化和毒力的调控以及细菌毒力的进化可能具有重要意义。     

产毒性和致病性大肠杆菌中小肠结肠炎耶尔森菌强毒力岛的检测

目的 了解小肠结肠炎耶尔森菌强毒力岛在产毒性和致病性大肠杆菌中的分布，探讨毒力岛在大肠杆菌中的结构和功能。方法 对毒力岛的关键基因irp2,fyua和asn-intB进行PCR扩增和DNA测序，并对irp2和fyua进行原位杂交。结果 在检测的93株肠产毒性大肠杆菌的10株肠致病性大肠杆菌基因irp2的检出率分别为32.25%(30/93)和30%（3/10),fyua的阳性率为21.51%(20/93)和30%（3/10）。而且这些阳性菌株中的毒力岛大部分连接到天门冬氨酸tRNA(asntRNA）位点。结论 小肠结肠炎耶尔森菌强毒力岛在产毒性和致病性大肠肝菌中较高的阳性率，对于大肠杆菌毒力的变化和毒力的调控以及细菌毒力的进化可能具有重要意义。     

肠致病性大肠杆菌毒力因子EspF对肿瘤坏死因子-α、白细胞介素-6和白细胞介素-8的影响

目的研究肠致病性大肠杆菌(EPEC)毒力因子EspF转染人肠上皮细胞(HIC)株时,血清肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)和IL-8水平的动态变化及与HIC凋亡的关系。方法以Annexin V FITC/PI双染流式细胞仪检测HIC的凋亡率,并用酶联免疫吸附测定法检测转染0、6、12、24、48 h细胞培养上清液中TNF-α、IL-6和IL-8浓度的变化。结果 EspF转染HIC后TNF-α、IL-6和IL-8活性均显著增加,HIC凋亡率在转染后逐渐增高,HIC凋亡率与TNF-α、IL-6和IL-8的水平呈正相关。结论 EspF可激活多种炎症介质和诱导HIC凋亡,EspF转染HIC后TNF-α、IL-6和IL-8水平的升高在EPEC致病过程中起重要作用。     

密码子优化的HPV16 L2E7基因在大肠杆菌中高效表达

目的提高HPV16L2E7融合基因在大肠杆菌中的表达水平,为中试研究提供高表达量的疫苗候选株。方法根据大肠杆菌偏爱密码子,利用Synthetic Gene Designer软件对L2E7全基因进行密码子优化,将分段合成的基因分部插入到pET9a中,经酶切和测序鉴定无误后转化BL21(DE3 )中,用异丙基-β-D硫代半乳糖苷(IPTG)诱导表达。表达的融合蛋白进行SDS-PAGE胶和Western blot鉴定。同时还进行梯度实验分别对诱导的温度、时间和IPTG诱导时菌体浓度进行优化,并对蛋白的纯化方案进行摸索。结果优化后的pET9aSL2E7AB在大肠杆菌中得到高效表达,诱导条件优化后的目的蛋白占全菌60%左右。结论成功得到了具有较高表达水平的疫苗候选株。     

呼吸道合胞病毒NS1基因原核表达及其免疫原性分析

目的:原核表达呼吸道合胞病毒(RSV)非结构NS1蛋白,并对其免疫特性进行研究.方法 采用PCR技术获得NS1基因,将其插入pET41a(+)载体上,导人大肠杆菌后诱导表达;利用GST亲和层析柱对诱导表达的NS1蛋白进行纯化,免疫动物制备抗体,Western blot法鉴定抗体的特异性.结果 重组质粒经酶切鉴定和DNA序列测序完全正确,经IPTG诱导后融合蛋白在大肠杆菌BL21-DE3中得到高效表达,表达产物经超声破碎和GST亲和层析纯化获得重组蛋白,分子量约42 000 Mr,以抗NS1蛋白的多克隆抗体为一抗进行Western blot检测,结果只有RSV感染细胞的样品在15 000 Mr处有特异性带显示,其他病毒感染的细胞和阴性对照没有相应条带.结论 NS1基因得到高效表达,免疫制备得到的抗体与RSV感染细胞有特异性反应,与其他常见呼吸道病毒感染细胞无交叉免疫反应.     

Multiplex Polymerase Chain Reaction for Rapid Identification of Diarrheagenic Escherichia coli

Despite the fact that diarrhaegenic Escherichia coli (DEC) has been identified as a major etiologic agent of childhood diarrhea which represent a major public health problem in developing countries, only a few studies have been performed in Bangladesh to identify these organisms. To detect DEC in patients with acute diarrhea, a total of 300 stool specimens were tested by multiplex polymerase chain reaction (PCR). The multiplex PCR was designed for the detection of target genes of "eae" for enteropathogenic E. coli (EPEC), "stx" for enterohemorrhagic E. coli (EHEC), "ipaH" for enteroinvasive E. coli (EIEC), "aspU", "CVD432" and "aggR" for enteroaggregative E. coli (EAEC) as well as "elt" and "est" for enterotoxigenic E. coli (ETEC). Out of 300 stool specimens collected from patients with acute diarrhea, the DEC was detected in 18% (54/300) cases. The dominating strain was ETEC (13%, 39/300), followed by EAEC (5%, 15/300) and no EHEC, EIEC and EPEC could be detected. Both heat-stable toxin (ST) and heat-labile toxin (LT) genes of ETEC were detected in 66.68% (26/39) strains and only ST or LT as single gene was detected in 23.07% (9/39) or 10.25% (4/39) strains respectively. The multiplex PCR assay could be used as a rapid as well as efficient diagnostic tool for identification of DEC in the clinical laboratory settings.     

Construction of the E.coli clone expressing adhesin BabA of Helicobacter pylori and evaluation of the adherence activity of BabA.

OBJECTIVE: To construct a recombinant E.coli strain that highly expresses blood group Ag-binding adhesin (BabA) of Helicobacter pylori (Hp) and to assess the adherence activity of Hp BabA. METHODS: The gene fragment encoding BabA was amplified from Hp chromosomal DNA by PCR technique and inserted into prokaryotic expression vector pET-22b (+), which was then transformed into BL21 (DE3) E.coli strain for the expression of BabA recombinant protein. The adherence activity of Hp BabA obtained was assayed by counting under light microscope. RESULTS: DNA sequence analysis showed that the sequence of babA2 DNA was in agreement with that published in GenBank. The BabA recombinant protein amounted to 34.8% of the total protein of the bacterium after IPTG induction for 3 h at 37 degrees Celsius, and BabA-mediated adherence was confirmed in vitro. CONCLUSION: A clone expressing biologically active Hp BabA has been obtained, which may facilitate further study of the function of the adhesin.     

合肥市新生儿感染性腹泻病原的调查

1988年3～5月对合肥市两所医院(甲、乙医院)婴儿室新生儿感染腹泻病原菌进行调查,336名新生儿中RV感染率14%,EPEC感染率2.1%,其余细菌未检出。乙医院感染率高于甲医院。发现同时感染RV和EPEC但不发病。提示新生儿可以携带RV和EPEC,其意义有待进一步研究。     

提高抗地高辛人单链抗体在大肠杆菌分泌型表达的研究

目的：提高从半合成噬菌体抗体库中克隆的抗地高辛（Dig）人单链抗体（ADAscFv）在大肠杆菌（E．coli）的分泌表达水平。方法：①通过PCR从表达质粒pHEN2－ADAscFv扩增ADAscFv基因并重组于质粒p3MH构建表达质粒p3MH－ADAscFv后，转化到E.coliXl1-blue及2151；②ADAscFv分别带有上述2种表达质粒的E.coliHB2151以及带有表达质粒p3MH－ADAscFv的E.coliXL1－blue进行表达，通过ELISA分析培养基上清中的可溶性ADAscFv；③在培养基中加入蔗糖、甘氨酸及TritonX-100，通过ELISA分析培养基上清中的可溶性ADAscFv。结果：①ADAscFv在含表达质粒p3MH－ADSAscFv的E.coliHB2151及XL1－blue的分泌型表达水平比pHEN2－E.coliHB2151表达系统高约5倍；②在培养其中加入蔗糖，可使ADAscFv在含有表达质粒p3MH-ADAscFv的E.coliHB2151及XL1－blue表达系统的分泌型表达提高5倍多。结论：通过采用不同的载体－E.coli表达系统以有在培养基中加入不被代谢的蔗糖，可使ADAscFv的分泌型表达提高25倍多。     

Soluble expression of active human β-defensin-3 in Escherichia coli and its effects on the growth of host cells

Background Human β-defensin-3 （HBD3） is an epithelial peptide that has been demonstrated to have a salt-insensitive broad spectrum of potent antimicrobial activity. Expressing antimicrobial peptides in Escherichia coil （E. colt） is very difficult for it can result in death of the bacterial host cells. Our aim was to establish a prokaryotic system expressing soluble HBD3 protein and demonstrate the antimicrobial activity of the expressed protein. We then studied whether the host cells would activate the suicide pathways. Methods We first cloned the complementary DNA coding for the mature chain of HBD3, inserted it into the vector PGEX-KG then transformed E. coil BL21 （DE3） with the appropriate recombinant plasmid. After induction with 0.5 mmol/L isopropyl-1-thio-β-D-galactopyranoside （IPTG） the transformed E. cofiproduced a recombinant glutathione S-transferase and HBD3 （GST-HBD3） fusion protein. The fusion protein was treated with thrombin to produce pure HBD3 protein then the antimicrobial activity of HBD3 was evaluated in a liquid microdilution assay. Results The fusion protein GST-HBD3 was efficiently cleaved by thrombin and yielded HBD3 that had anti-staphylococcus aureus activity with a minimal inhibitory concentration level of 12.5 μg/ml. The E. coil strain expressing the recombinant protein did not grow slower than the empty vector strain. Conclusion Active HBD3 in E. coil by expressing the recombinant protein GST-HBD3 could be produced, and suicide did not occur in the E. coli strain expressing the recombinant protein.     

同种异体单核细胞活化血管内皮细胞产生IP-10、I-TAC的体外研究

目的  研究单核细胞对异体血管内皮细胞（VEC）的活化作用以及产生干扰素诱导蛋白10（IP-10）、干扰素诱导的T细胞α型趋化因子（I-TAC）的效果。方法  人外周血中分离单核细胞，酶消化法分离人主动脉内皮细胞，建立单核细胞与VEC共培养系统。用流式细胞仪（FACS）检测VEC表面粘附分子CD54、CD62E表达的情况，用RT-PCR检测VEC内I-TAC和IP 10 mRNA的表达情况。结果  RT-PCR 检测结果表明，VEC与同种异体单核细胞共培养24h后，细胞内IP-10和I-TAC mRNA表达水平显著增加（P<0.05），且在48、72h的表达维持在较高的水平。 FACS检测结果表明，正常培养的VEC少量表达CD54分子，不表达CD62E分子。与同种异体单核细胞共培养24h后，VEC表面CD62E和CD54的表达水平明显上调（P<0.05）。结论  在同种异体单核细胞 血管内皮细胞免疫反应中，单核细胞能活化血管内皮细胞，使内皮细胞表达IP-10、I-TAC等趋化因子和CD54、CD62E等粘附分子，参与对移植器官的排斥反应。     

Molecular detection and antimicrobial resistance of diarrheagenic Escherichia coli strains isolated from diarrheal cases

OBJECTIVE: To identify and classify Iranian isolates of diarrheagenic Escherichia coli (E. coli) on the basis of presence of virulence genes and to determine antibiotic susceptibility of isolated strains. METHODS: The current cross-sectional study was conducted in 2005 at the Pasteur Institute, Tehran, Iran. One hundred and ninety-three diarrheagenic E. coli isolated from diarrheal patients in different regions of Iran were included in current study. Virulence factor genes for diarrheagenic E. coli were detected by polymerase chain reaction. RESULTS: Of the 193 diarrheagenic E. coli detected by PCR, 86 (44.5%) were Shiga toxin-producing E. coli STEC, 74 (38.4%) enteropathogenic E. coli EPEC, 19 (9.8%) enteroaggregative E. coli, and 14 (7.3%) enterotoxigenic E. coli isolates. Susceptibility to 12 clinically important antimicrobial agents was determined for 193 strains of diarrheagenic E. coli. A high incidence of resistance to tetracycline (63%), ampicillin (62%), streptomycin (56%), amoxicillin/clavulanic acid (44.5%), trimethoprim/sulfamethoxazole (39.5%), and cephalothin (37%) was observed. CONCLUSION: The STEC and EPEC strains with high resistance to tetracycline and ampicillin, but highly susceptible to quinolones are among the most important causative agent of diarrhea in Iran. This study suggests that antimicrobial resistance is widespread among E. coli strains colonizing Iranian patients. Guidelines for appropriate use of antibiotics in developing countries require updating.     

人胶质细胞源性神经营养因子(hGDNF)成熟肽基因的克隆及原核表达

目的分离人胶质细胞源性神经营养因子(hGDNF)成熟肽基因，并在E．coil中获得表达。方法以人的白细胞基因组DNA为模板，合成特异引物，采用PCR技术分离得到hGDNF成熟肽基因，并构建表达载体pET-21a( )-hGDNF，转化大肠杆菌BL21(DE3)，分别用IPTG和乳糖诱导表达，SDS-PAGE电泳检测hGDNF蛋白表达。结果PCR扩增出了400bp的DNA片段，构建的表达载体pET-21a( )-hGDNF经酶切、PCR鉴定均出现400bp左右的条带，测序结果正确，用IPTG或乳糖诱导转化菌均有15kd大小的目的条带，表达的目的蛋白占菌体总蛋白30％以上，以包涵体形式存在。结论克隆得到人GDNF成熟肽基因并在大肠杆菌中得到了高效表达。     

Preparation of Monoclonal Antibody and Development of Enzyme-linked Immunosorbent Assay Specific for Escherichia coil O157 in Foods

OBJECTIVE: To prepare monoclonal antibodies (MAb) and antisera specific for Escherichia coli (E. coli) O157, and to develop a sandwich enzyme-linked immunosorbent assay (ELISA) to detect E. coli O157 in foods. METHODS: Spleen cells from BALB/c mice immunized with the somatic antigen of E. coli O157:H7 were fused with murine Sp2/0 myeloma cells. The hybridoma cell line specific for E. coli O157 was established after having been subcloned. Antisera specific for E. coli O157 was prepared by intravenous injection into New Zealand rabbits with a stain of E. coli O157:H7. The sandwich ELISA was developed with the polyclonal antibody as the capture antibody and the MAb 3A5 as the detection antibody. The inoculated ground poultry meat and pasteurized milk were tested to confirm efficiency of the method. RESULTS: MAb 3A5 specific for E. coli O157 and O113:H21 belonged to subtype IgM. The ascetic titers of the antibody was 1:1x10(6). No cross-reactivity of the MAb was observed with strains of Salmonella spp, Yersinia enterocolitica, Shigella dysenteriae, etc. The purified polyclonal antibody had a titer of 1:1x10(5) with E. coli O157. The detection limit of this sandwich ELISA was 10(3)-10(4) cfu E. coli O157/mL in pure culture with a high specificity, which was characterized by every non-O157 strain with negative response. With 10h enrichment procedure, E. coli O157:H7 recovered well from inoculated ground poultry meat and pasteurized milk at levels of 0.1 cfu/g and 0.1 cfu/mL. CONCLUSION: MAb 3A5 specific for E. coli O157 and O113:H21 can be produced by immunizing BALB/c mice with a strain of E. coli O157:H7. Then a sandwich ELISA can be developed with the polyclonal antibody as the capture antibody and the MAb 3A5 as the detection antibody. The method is proved to be a sensitive and specific technique to detect low number of E. coli O157 in food.     

携带毒力岛大肠杆菌性小儿腹泻

目的：探讨携带毒力岛大肠杆菌（HPIEC）在小儿腹泻中的病原学地位。方法：采用PCR扩增和菌落原位杂交检测HPIEC－irp2毒力岛基因,并用血清学分型和聚合酶链反应（PCR）法检测各类致泻大肠杆菌。结果：从1032例腹泻患者粪便中分离出652株大肠杆菌,经血清学和PCR毒力基因分型,检出各类致泻大肠杆菌225株,其中肠致病性大肠杆菌（EPEC）20株,ETEC81株,产志贺样毒素大肠杆菌（SLTEC）47株,产志贺样毒素侵袭性大肠杆菌（ESIEC）74株,产毒素大肠杆菌（EIEC）3株。所有致泻大肠杆菌和未能分型的普通大肠杆菌株,再用HPIEC－irp2探针作菌落原位杂交,共检出携带毒力岛大肠杆菌（HPIEC－irp2)112株,总阳性率为17．2％。其中41例是从致泻大肠杆菌ESIEC（24／74）和SLTEC（17／47）中检出。携带毒力岛大肠杆菌性小儿腹泻的主要临床表现为食欲不振（87．5％）,腹痛（58．0％）,腹泻（＞6次／d,75．9）,发热（50．9％）,以粘液便为主（69．6％）。结论：携带毒力岛大肠杆菌是引起小儿腹泻的重要病原菌之一。     

DinB基因的超表达短期内可显著降低大肠杆菌的死亡率

 [目的]探讨大肠杆菌dinB基因在进化上的选择优势.[方法]应用竞争共培养和超表达的策略,测定共培养后含dinB基因的目的菌株和对照菌株的生长优势.第1组为含质粒pUC-dinB-rrnb的E.coli AB1157＋含质粒pUC-dinBR-rrnb的E.coli YG7207;第2组为含质粒pUC-dinB-rrnb的E..coli AB1157＋含质粒pUC-phoE-rrnb的E.coli YG7207;第3组为含质粒pUC-phoE-rrnb的E.coli AB1157＋含质粒pUC-dinBR-rrnb的E.coli YG7207;第4组为卡那霉素抗性（K^＋）菌株YG7207与无卡那霉素抗性菌株AB1157.[结果]第4组中,卡那霉素抗性菌株YG7207与无卡那霉素抗性菌株AB1157在培养物中的比例保持着良好的稳定.第1组和第2组混合培养中,K^＋抗性的菌株在培养物中的比例急剧下降,并很快接近或等于0;第3组培养物中,K^＋菌株（YG7207）的比例呈明显上升.[结论]超表达dinB基因的大肠杆菌菌株的生长优势不是由于对数期的生长速率提高所造成,对数后期细胞死亡率降低应该是超表达dinB基因的大肠杆菌菌株的生长优势的主要原因.     

Observation of monoclonal antibody E4B7D5 inhibitory effect on leptospiral adherence using scanning electron microscope]

BALB/c mice were immunized intraperitoneally with outer envelopes of serogroup icterohaemorrhagiae lai serovar strain 017 leptospires. Monoclonal antibody (McAb) E4B7D5 against outer envelopes (IgG1, agglutinating titre 1:25,600) was produced by hybridoma technique. Passive immunoprotection experiments have demonstrated the immunoprotection of McAb E4B7D5 against strain 017 leptospires. Effect of McAb E4B7D5 on leptospiral adherence to the surface of normal human pulmonary embryonic fibroblasts was observed by using scanning electron microscope. The results indicated that the leptospiral adherence noted in various agglutinating titre McAb E4B7D5 groups was less frequent than that in the three control groups. It was concluded that the inhibitory effect of McAb E4B7D5 on leptospiral adherence may play a role in the immunoprotection.