13株杨氏枸橼酸杆菌的黏附、细胞毒性和耐药性检测

目的 了解杨氏枸橼酸杆菌（CY）的黏附、细胞毒性和耐药情况。方法 对从安徽省马鞍山市腹泻病例分离到的13株CY开展黏附HEp-2细胞的检测,同时对HEp-2细胞（MOI:100）作用8 h后的乳酸脱氢酶（LDH）释放情况以及对15种抗生素的药敏实验进行分析。结果 5株CY几乎没有黏附性,黏附指数1;6株CY具有中等黏附性,黏附指数1,且50;2株CY具有强的黏附性,黏附指数50。与HEp-2细胞作用8 h后,3株菌引起的LDH释放量20.00%,其余10株菌引起的LDH释放量均20.00%。13株CY对环丙沙星和妥布霉素均敏感（100%）,对氨苄西林和头孢唑啉的耐药率最高（92.30%）。CY1对7种抗生素耐药,属于多重耐药菌,并且具有强的细胞毒性。结论 本研究共检测出3株强细胞毒性的CY和7株多重耐药的CY,建议临床关注枸橼酸杆菌的毒性和多重耐药情况。     

弗氏枸橼酸杆菌CF74的T6SS影响FliC的表达和分泌

目的 研究弗氏枸橼酸杆菌CF74的T6SS基因组岛功能。方法 构建弗氏枸橼酸杆菌CF74的T6SS基因组岛的精确缺失突变株(CF74T6SS)。对弗氏枸橼酸杆菌CF74和其突变株CF74T6SS的全菌蛋白和上清蛋白进行提取,并进行2-DE分析。结果 在CF74T6SS全菌蛋白中,有4个蛋白表达上调,42个蛋白表达下调,并且FliC的表达下调十分明显;在CF74T6SS的培养上清中,有27个蛋白表达上调,36个蛋白表达下调,并且FliC、FlgK和FliD的表达下调十分明显。结论 弗氏枸橼酸杆菌CF74的T6SS可以影响FliC蛋白的表达和分泌。     

肠集聚性大肠埃希菌分离株脉冲场凝胶电泳分析

目的 对我国散发腹泻患者肠集聚性大肠埃希菌(EAEC)分离株进行脉冲场凝胶电泳(PFGE)分析,以了解其分子流行病学特征并初步建立我国EAEC菌株的基础数据库。 方法 参照PulseNet大肠埃希菌O157:H7的PFGE实验方法对52株EAEC分离株进行分析,并使用BioNumerics软件进行聚类。 结果 在限制性内切酶XbaⅠ和PulseNet推荐的电泳参数下,菌株基因组酶切片段分布均匀,条带易于识别。52株EAEC分离株产生了48种PFGE带型,初步聚类为A~N 14个群,不同地区来源及不同HEp-2细胞黏附表型的菌株广泛分布在不同PFGE聚类群中。 结论 我国散发腹泻患者EAEC分离株呈现高度多态性,PFGE电泳参数和限制性内切酶XbaⅠ适用于我国EAEC菌株的分析。     

枸橼酸杆菌的生化鉴定

枸橼酸杆菌(C.)属G-菌,氧化酶阴性,有动力,利用枸橼酸盐为唯一的碳源,其V-P试验及赖氨酸脱羧酶试验均阴性。伯氏分类手册将C.分为弗氏(C.freundii)、异型(C.kosevi),无丙二酸(C.a-malonaticus)。近来Brennev据在60℃和75℃进行的DNA相关性研究提出无丙二酸C.中存在另一种,名为C.farmeri,并提出弗氏C.复合体中至少存在8种独特的DNA基因组,4个新种被命名为C.youngae,C.braakii,C.werkmanii,C.sedlakii,尚有三个种因菌株量少而不能命名。作者等收集了235株C.对其进行生化鉴定以确定其种。据吲哚。H_2S.     

弗氏枸橼酸杆菌TaqMan实时荧光定量-聚合酶链反应检测方法的建立

目的 建立针对弗氏枸橼酸杆菌的TaqMan实时荧光定量-聚合酶链反应(real time-PCR)检测方法。 方法 针对弗氏枸橼酸杆菌的特有序列设计引物和TaqMan探针,扩增目的基因建立标准曲线,确定检测方法的灵敏度;对20种其他肠道致病菌及院内感染中常见的致病菌进行检测,评价该检测方法的特异性;使用牛奶模拟标本评价方法在实际检测工作中应用性。 结果 TaqMan real time-PCR检测方法对弗氏枸橼酸杆菌重组质粒的检测灵敏度为1.0101拷贝／反应体系;该检测方法在检测30种其他肠道致病菌及院内感染中常见的致病菌时未出现特异性扩增。该检测方法对牛奶模拟样本中弗氏枸橼酸杆菌检测下限为1.0102cfu/ml的菌量;通过对1.0107、1.0105和1.0103三个浓度质粒标准品的重复检测,确定本方法的组内变异系数为1.90%~3.91%;组间变异系数为1.52%~1.69%。 结论 本研究建立的TaqMan real time-PCR检测方法可作为检测弗氏枸橼酸杆菌灵敏、特异、快速的方法。     

安徽省马鞍山市分离的枸橼酸杆菌的分子分型

目的 了解中国安徽省马鞍山市分离到的枸橼酸杆菌的分子流行病学特征。方法 2007-2011年从安徽省马鞍山市的腹泻患者粪便、食品和食品加工者肛拭分离到62株枸橼酸杆菌,包括13株弗氏枸橼酸杆菌、41株杨氏枸橼酸杆菌和8株布氏枸橼酸杆菌。所有菌株用Xba Ⅰ酶切进行脉冲场凝胶电泳（PFGE）分型和扩增7个管家基因的多位点序列分型（MLST）分析。结果 PFGE将62株枸橼酸杆菌分成43个带型（PTs）,MLST将其分成53个ST型别（STs）。CITX01.CN0039是PFGE的优势带型,由2007-2008年间从食品和腹泻患者粪便分离的7株杨氏枸橼酸杆菌组成。53个ST型别分成5个ST序列群,ST序列群39个优势菌株来自腹泻患者粪便、食品和食品加工者肛拭分离的枸橼酸杆菌。从腹泻患者粪便、食品和食品加工者肛拭分离得到的枸橼酸杆菌具有相同的PTs和STs。结论 在食品和人群中监测枸橼酸杆菌对预防和控制枸橼酸杆菌引起的腹泻是必要的。     

黄曲霉毒素B1对非洲绿猴肾细胞的毒性效应及作用机制研究

目的探讨黄曲霉毒素B1(AFB1)对非洲绿猴肾细胞(Vero E6)的毒性效应及其作用机制。方法体外培养Vero E6细胞,不同浓度AFB1处理细胞后,采用CCK-8法检测细胞存活率;检测乳酸盐脱氢酶(LDH)释放率;利用Annexin V/PI双染、DAPI染色研究细胞死亡机制。结果 AFB1对Vero E6细胞有显著毒性损伤效应,200μmol/L AFB1处理Vero E6细胞48h后,细胞存活率不到10%。细胞LDH释放率随着AFB1浓度增加而显著升高。Annexin V/PI染色检测到细胞膜磷脂酰丝氨酸外翻。DAPI染色检测到细胞核碎裂。结论 AFB1对Vero E6细胞具有明显的毒性损伤作用,其可能通过凋亡的机制引起细胞死亡。     

促肾上腺皮质激素对脐静脉内皮细胞株及星形胶质细胞的毒性作用研究

目的 探讨促肾上腺皮质激素[ACTH(1-24) ]对脐静脉内皮细胞株(ECV304)和星形胶质细胞的细胞毒性作用.方法 采用体外细胞培养技术,以细胞形态学、细胞活性、乳酸脱氢酶(LDH)释放量及细胞凋亡率的改变为指标,观察不同浓度的ACTH(1-24) 对ECV304和星形胶质细胞的影响.结果 ACTH(1-24)血药浓度在1 μg/ml、5 μg/ml、25 μg/ml、100 μg/ml、200 μg/ml范围内对ECV304和星形胶质细胞的形态、细胞活性、凋亡率及LDH的释放均无明显影响,组间比较差异无统计学意义(P＞0.05).结论 ACTH(1-24)在1～200 μg/ml的浓度范围内对ECV304和星形胶质细胞均无毒性作用.     

局灶性节段性肾小球硬化患者血清对体外培养足细胞凋亡和黏附功能的影响

目的 探讨局灶性节段性肾小球硬化(FSGS)患者血清对体外培养足细胞凋亡和黏附功能的影响.方法 提取原发性FSGS患者和正常人血清,分别以20%正常血清、5%、10%、20%FSGS血清孵育体外培养足细胞24 h.48 h,乳酸脱氢酶(LDH)释放实验检测足细胞活力,Hoechst33258法检测足细胞凋亡率,分光光度法检测足细胞caspase-3酶活性,并检测足细胞黏附能力.结果 FSGS患者血清呈时间和浓度依赖性地升高足细胞LDH释放率(与同时间点正常血清组比较,P分别相似文献   

266株腹泻病原菌的分布及耐药性分析

目的：了解我院急、慢性腹泻病人的菌群分布及耐药性特征，为临床用药提供依据。方法：应用回顾性调查分析的方法，对我院近4年腹泻病人大便中分离的266株病原菌进行统计并对常见细菌耐药率进行分析。结果：急性腹泻病人最常见的是福氏志贺菌，食物中毒引起的腹泻最常见的是沙门氏菌和弗氏枸橼杆菌，慢性腹泻病人最常见的是弗氏枸橼酸杆菌，其次是变形杆菌、亚利桑那菌和白色念珠菌。分离菌株中耐药性以氨苄西林、头孢唑啉的耐药率最高，达(33％～92％)，对亚胺培南、第四代头孢菌素较敏感，敏感率在90％以上。弗氏枸橼酸杆菌产AmpC酸占33％。结论：腹泻病人的病原菌都有不同程度的耐药性，进行常规的耐药性监测，根据药敏试验合理应用抗菌素十分重要。     

Enteroaggregative Escherichia coli expresses a novel flagellin that causes IL-8 release from intestinal epithelial cells

Enteroaggregative Escherichia coli (EAEC) is an emerging cause of acute and persistent diarrhea worldwide. EAEC infections are associated with intestinal inflammation and growth impairment in infected children, even in the absence of diarrhea. We previously reported that prototype EAEC strains rapidly induce IL-8 production by Caco-2 intestinal epithelial cells, and that this effect is mediated by a soluble, heat-stable factor released by these bacteria in culture. We herein report the cloning, sequencing, and expression of this biologically active IL-8-releasing factor from EAEC, and its identification as a flagellin that is unique among known expressed proteins. Flagella purified from EAEC 042 and several other EAEC isolates potently release IL-8 from Caco-2 cells; an engineered aflagellar mutant of 042 does not release IL-8. Finally, cloned EAEC flagellin expressed in nonpathogenic E. coli as a polyhistidine-tagged fusion protein maintains its proinflammatory activity. These findings demonstrate a major new means by which EAEC may cause intestinal inflammation, persistent diarrhea, and growth impairment that characterize human infection with these organisms. Furthermore, they open new approaches for diagnosis and vaccine development. This novel pathogenic mechanism of EAEC extends an emerging paradigm of bacterial flagella as inflammatory stimuli.     

Translocation of antibiotic resistance determinants including an extended-spectrum beta-lactamase between conjugative plasmids of Klebsiella pneumoniae and Escherichia coli.

The extended-spectrum beta-lactamase CAZ-7, derived from TEMs, was produced by two different strains of the family Enterobacteriaceae, Klebsiella pneumoniae and Escherichia coli, isolated from the same patient. Both isolates were resistant to amikacin. In addition, the K. pneumoniae strain was TEM-1 producing and resistant to gentamicin. An E. coli HB101 transconjugant obtained from K. pneumoniae, selected on ceftazidime, showed that CAZ-7 and amikacin resistance were encoded by an 85-kb Inc7 or M plasmid, while an E. coli HB101 transconjugant obtained from E. coli under the same conditions showed that CAZ-7 and amikacin resistance were encoded by a greater than 150-kb Inc6 or C plasmid. Two other E. coli HB101 transconjugants obtained from K. pneumoniae, selected on gentamicin or chloramphenicol, showed that TEM-1 and gentamicin resistance could be encoded either by a greater than 150-kb Inc6 or C plasmid or by an 85-kb Inc7 or M plasmid. It was hypothesized that the genes for beta-lactam and aminoglycoside resistances were located on translocatable sequences. EcoRI digestion and hybridizations obtained with blatem, aacA4, and IS15 probes demonstrated that the CAZ-7 gene, amikacin resistance gene, and IS15 element were clustered on an approximately 20-kb fragment common to 85- and greater than 150-kb plasmids. E. coli HB101 transconjugants from K. pneumoniae and E. coli isolates were used to obtain translocations of CAZ-7 and amikacin resistance and of TEM-1 and gentamicin resistance between the 85- and greater than 150-kb plasmids. This study shows a typical example of in vivo gene dissemination involving transposable elements which translocate multiresistance genes, including an extended-spectrum beta-lactamase.     

北京市朝阳区腹泻患者致泻性大肠埃希菌流行特征及毒力基因携带情况分析

目的分析北京市朝阳区感染性腹泻样本中致泻性大肠埃希菌（DEC）流行特征及毒力基因携带情况。方法收集2014 — 2017年北京市朝阳区哨点医院感染性腹泻样本,分离培养后应用real-time PCR方法检测DEC的主要毒力基因。 其中利用eae、stx1、stx2、lt、st、aggR和ipaH 7种毒力基因进行DEC的分型鉴定,此外,检测并分析bfpA、astA、escV、pic、perA、ehxA、pet和ipaBCD等重要的毒力基因分布情况。结果从1 977份腹泻样本中共分离出94株DEC,检出率为4.75%。 DEC的检出率具有随年龄增加而升高的趋势。 0 ~ 5岁年龄组肠聚集性大肠埃希菌（EAEC）和肠致病性大肠埃希菌（EPEC）构成比分别是59.62%、23.08%。 5岁以上年龄组肠产毒性大肠埃希菌（ETEC）构成比是59.52%。 81.25%EPEC（13/16）未携带bfpA,为非典型EPEC（aEPEC）。 38株EAEC中astA、pic和pet的携带率分别为39.47%、68.42%和92.11%。 30株ETEC的st、lt和astA携带率分别是46.67%、56.67%和53.33%;仅1株（3.33%）ETEC同时含有st和lt。 4株EHEC全部携带 eae、escV和ehxA。 6株肠侵袭性大肠埃希菌（EIEC）中ipaBCD、astA携带率为16.67%和33.33%。结论北京市朝阳区流行的DEC以EAEC、ETEC和EPEC为主,其中EPEC主要为aEPEC。 婴幼儿主要感染EAEC,成年人主要感染ETEC。 DEC中存在多种毒力基因,其中astA广泛存在于多种DEC中。     

2013-2020年北京市海淀区成年人致泻大肠埃希菌流行特征和分型研究

目的 掌握北京市海淀区成年人致泻大肠埃希菌(DEC)流行特征和脉冲场凝胶电泳(PFGE)分型特点.方法 对2013-2020年在3家哨点医院就诊的1961例成年人腹泻患者粪便或肛拭子标本进行DEC检测,对其中66株DEC菌株进行PFGE分型试验.结果 成年人DEC检出率为9.54％(187/1961),产肠毒素大肠埃希...     

Development of resistance to cephalosporins in clinical strains of Citrobacter spp.

The predominant beta-lactam antibiogram of Citrobacter freundii resembles that of Enterobacter cloacae in demonstrating resistance to cephalothin and cefoxitin with susceptibility to the newer cephalosporins. Four representative strains of C. freundii were reversibly induced to high-level beta-lactamase production by cefoxitin, and mutants with stable, high-level production were selected with cefamandole. The mutants were resistant to several second- and third-generation cephalosporins. Comparisons of isoelectric points and substrate profiles of beta-lactamases from wild-type, induced wild-type, and mutant organisms suggested a close relationship to those from E. cloacae and indicated that C. freundii mutants, like those of E. cloacae, were derepressed for production of beta-lactamase. One primary isolate of C. freundii resembled the mutants in all characteristics. In contrast, most strains of Citrobacter diversus were susceptible to all cephalosporins, and two representative strains showed neither inducible nor mutational resistance. Cefoxitin induction to enhanced beta-lactamase production was demonstrated in a cephalothin-resistant isolate, and a derepressed mutant was selected with cefotaxime. The beta-lactamase from this C. diversus strain differed substantially in substrate profile from that of E. cloacae and C. freundii.     

Chromosomal beta-lactamase of Klebsiella oxytoca, a new class A enzyme that hydrolyzes broad-spectrum beta-lactam antibiotics

The chromosomally encoded beta-lactamase gene of Klebsiella oxytoca E23004, a strain resistant to cefoperazone and aztreonam, was cloned and expressed in Escherichia coli HB101. The molecular mass and pI of this enzyme were 28 kilodaltons and 7.4, respectively. Although the beta-lactamase of K. oxytoca hydrolyzed many cephalosporins, including broad-spectrum drugs, the nucleotide sequence and deduced amino acid sequence lacked homology with chromosomal class C beta-lactamase genes (ampC) of E. coli or Citrobacter freundii. Rather, about 45% nucleotide sequence homology and 40% deduced amino acid sequence homology were observed between the K. oxytoca beta-lactamase and TEM-1, a class A beta-lactamase which does not efficiently hydrolyze cephalosporins. Values of Km, relative Vmax, and relative Vmax/Km for the K. oxytoca beta-lactamase indicated that the enzyme is a penicillinase but that it can hydrolyze cefoperazone effectively and other broad-spectrum cephems weakly. Hence, the chromosomal beta-lactamase of K. oxytoca E23004 belongs to class A but differences in its amino acid sequence provide a broader spectrum of activity.     

Role of the eaeA gene in experimental enteropathogenic Escherichia coli infection.

Enteropathogenic Escherichia coli (EPEC) infections are a leading cause of infant diarrhea in developing countries. Recently eaeA, a gene necessary for the characteristic intimate attachment of EPEC to epithelial cells in tissue culture, was described. We conducted a randomized, double-blind study to determine the role of the eaeA gene in human EPEC infection. 11 adult volunteers ingested 2 x 10(10) colony-forming units of O127:H6 EPEC strain E2348/69, and an equal number received the same dose of an isogenic eaeA deletion mutant constructed from E2348/69. Volunteers were monitored for the development of diarrhea, fever, and systemic and gastrointestinal complaints. Diarrhea developed in all 11 volunteers who received E2348/69 and in 4 of 11 who received the mutant (P = 0.002). Fever was more common in recipients of the wild-type strain (P = 0.024). Stool volumes were lower in recipients of the mutant. All volunteers seroconverted to E2348/69 LPS, but the geometric mean peak titers of serum IgG and IgA in recipients of the mutant were lower than those of recipients of the wild-type strain. IgA against LPS was detected in the jejunal fluid of six of six recipients of E2348/69 and 5/6 recipients of the mutant. This study unambiguously assigns a role for eaeA as an EPEC virulence gene, but the residual diarrhea seen in recipients of the mutant indicates that other factors are involved.     

Concomitant dissemination of three extended-spectrum beta-lactamases among different Enterobacteriaceae isolated in a French hospital.

From January 1988 to August 1989, 267 non-repetitive strains of Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBla) derived from TEM (CTX-1/TEM-3, CAZ-6) or SHV (CAZ-5) were isolated from 219 colonized or infected patients. ESBlas were characterized by analytical isoelectric focusing. Biotypes, resistance phenotypes and plasmid patterns were determined in order to differentiate the isolates in each species. Among the 116 CTX-1-producing Enterobacteriaceae, 48 strains were differentiated: 27 from 74 Klebsiella pneumoniae isolates, seven from 22 Enterobacter aerogenes isolates, and 14 from a combined total of seven K. oxytoca, five Serratia marcescens, six Escherichia coli, 1 Enterobacter cloacae and 1 Citrobacter freundii. CAZ-5 has been isolated since January 1988 in 16 different strains among 101 K. pneumoniae isolates. CAZ-6 was first identified in K. pneumoniae (January 1988). Among the 48 Enterobacteriaceae producing CAZ-6, 12 strains were differentiated: four from 39 E. aerogenes isolates, three from four K. pneumoniae, and five from a combined total of two S. marcescens, two E. coli and one E. cloacae. During this outbreak, CTX-1 was found to be encoded by 85 kb (Inc 7/M) or greater than or equal to 150 kb (Inc 6/C) plasmids. CAZ-6 was always encoded by an 85 kb (Inc 7/M) plasmid and CAZ-5 by a greater than 150 kb plasmid. These results show that strain epidemics and plasmid dissemination occurred mainly in K. pneumoniae and E. aerogenes for CTX-1, in E. aerogenes for CAZ-6, and in K. pneumoniae for CAZ-5. They also suggest that the bla(tem) gene (CTX-1) has spread between different plasmids present in the same ecosystem.