对甲硝唑耐药幽门螺杆菌中rdxA基因的表达

目的 探讨对甲硝唑耐药幽门螺杆菌(Hp)株中rdxA基因表达的差异。方法 随机收集51例快速尿素酶试验阳性患者的胃窦部黏膜,体外微需氧培养。甲硝唑耐药率检测分别用E试验和临界点药敏法。选取对甲硝唑高度耐药菌株(MIC值>256 mg/L),在含16 mr/L甲硝唑及不含甲硝唑培养基中分组培养,半定量RT-PCR法检测rdxA基因的表达,用galE基因作外参照。结果 共分离出Hp临床分离菌47株。E试验法甲硝唑耐药率为34％(16/47),临界点药敏法为32％(15/47),其中15株(包括5株高度耐药菌株)2种方法均耐药。5株高度耐药菌中rdxA基因在甲硝唑存在的情况下表达量减少,而参照galE基因表达均不变。结论rdxA基因的表达减少在Hp对甲硝唑高度耐药形成中起了一定的作用。     

幽门螺杆菌对甲硝唑耐药机制的研究进展

幽门螺杆菌（Hp)对甲硝唑耐药的主要机制是rdxA基因的突变失活；同时，frxA基因和fdxB基因的突变失活可增加Hp的甲硝唑耐药性。此外，还存在其它耐药机制，本就目前Hp对甲硝唑耐药机制作一综述。     

幽门螺杆菌对甲硝唑耐药机制的研究进展

幽门螺杆菌(Hp)对甲硝唑耐药的主要机制是rdxA基因的突变失活;同时,frxA基因和fdxB基因的突变失活可增加Hp的甲硝唑耐药性。此外,还存在其它耐药机制。本文就目前Hp对甲硝唑耐药机制作一综述。     

幽门螺杆菌对甲硝唑耐药机制的探讨

目的 探讨幽门螺杆菌（Ｈｐ）对甲硝唑的耐药机制。方法 （１）甲硝唑选择压力试验;（２）ＳＤＳ－ＰＡＧＥ电泳;（３）硝酸盐还原试验;（４）革兰阴性菌９５种底物相关酶类检测。结果 Ｈｐ由敏感株突变为耐药株后,１－甲基琥碧酸、琥碧酸、Ｄ－丙酸相关酶类活性降低;Ｌ－岩藻糖、６－磷酸葡萄糖相关酶类活性增高。结论 Ｈｐ耐药性与细菌的代谢状态及酶系统的变化具有一定的相关性。     

维拉帕米对幽门螺杆菌甲硝唑耐药性的作用

目的探讨钙离子拮抗剂维拉帕米对幽门螺杆菌甲硝唑耐药性的作用和机制。方法 以药物梯度平皿筛选得到耐甲硝唑的Ｈｐ菌株，采用试管肉汤二倍稀释法的间接酶联免疫吸附法等测定Ｈｐ对甲硝唑等抗生素的最低抑菌浓度和维拉帕米对其的影响及维拉帕米在Ｈｐ摄取，外排甲硝唑中的作用结果 维拉帕米能降低Ｈｐ耐药菌株对甲硝唑的ＭＩＣ，提高甲硝唑对Ｈｐ的体外抗菌活性，增加Ｈｐ对多种抗生素的敏感性。     

幽门螺杆菌不同基因型和基因亚型与甲硝唑耐药性的研究

目的研究Helicobacter pylori菌株本身的毒力差异是否与H.pylori菌株对甲硝唑的敏感性有关。方法 用E-test方法检测109株H.pylori菌株对甲硝唑的敏感性;PCR检测H.pylori菌株不同的vacA基因亚型、cagA、iceA和babA2基因型。结果 云南地区甲硝唑耐药率为67.89％;vacA、cagA、iceAl、babA2基因的各种基因亚型和基因型在H.pylori菌株甲硝唑耐药率上无显著性差异。结论 H.pylori菌株本身的毒力差异与H.pylori菌株对甲硝唑的敏感性无关。     

幽门螺杆菌对甲硝唑的耐药性分析

目的探讨幽门螺杆菌（Helicobacter pylori,Hp）甲硝唑耐药菌株相关基因的突变与耐药性的关系。方法收集临床60例有胃部不适患者的胃活检组织,微需氧培养得到Hp菌株。E-Test法检测Hp对甲硝唑的最低抑菌浓度（MIC）,PCR扩增rdxA、frxA、fdxB,并对该基因进行测序,对耐药株的rdxA、frxA、fdxB的基因序列与标准株Hp26695相应序列进行同源性分析。结果 60例病人胃粘膜标本成功分离出11株Hp耐甲硝唑株（MIC均≥256μg/mL）。11株临床株和1株国际标准测序株（Hp26695）均扩增出rdxA、frxA、和fdxB;基因rdxA、fdxB和frxA突变有一定的规律性,除了存在共同突变外,还存在随机位点散在突变。结论 Hp对甲硝唑耐药性与rdxA、fdxB和frxA基因突变相关。     

幽门螺杆菌耐药分子机制研究进展

幽门螺杆菌(Helicobactef pylon,H pvlori)是慢性活动性胃炎的病原菌,是慢性胃炎和消化性溃疡的主要病因,与人体胃、十二指肠的疾病密切相关,并诱发胃癌的发生.随着抗生素药物的广泛使用,H pylori耐药株也日异增多,给临床H pylori的治疗带来巨大的困难.本文对H pylori的耐药现状与趋势进行分析,系统地综述了大环内酯类药物、硝基咪唑类药物、四环素类、β-内酰胺类物药物、喹诺酮类药物对H pylori的耐药情况.探讨对于每种药物的耐药机制及耐药类型检测的不同手段,为与H pylori导致的相关疾病的临床诊断、治疗提供可靠的依据,积累临床资料.     

幽门螺杆菌耐药的分子机制研究现状

近年抗生素耐药率普遍升高,耐药成为根除幽门螺杆菌治疗失败的主要原因.克拉霉素耐药的主要原因为23S rRNA基因点突变.甲硝唑低水平耐药主要与硝基还原酶基因rdxA和frxA基因的失活有关,高水平耐药是多基因突变的累积效果所致.阿莫西林耐药与pbp1A基因多位点突变相关.porD和oorD两基因的突变可能与幽门螺杆菌对呋喃唑酮产生低水平耐药相关.     

幽门螺杆菌耐药问题研究进展

研究表明，幽门螺杆菌的耐药性是造成根除Ｈｐ失 主要原因，已日益受到人们的关注。Ｈｐ对大环内酯类，硝基咪类、喹 耐药机制不同，耐药率在世界各地区也有很大判别探寻耐药病例的治疗方案成为临床研究所面临的问题。     

克拉维酸降低幽门螺杆菌对甲硝唑耐药性的体外观察和机制探讨

目的 探讨克拉维酸(CLA)降低幽门螺杆菌(Hp)对甲硝唑(MZ)耐药性的体外作用及机制.方法 由胃镜活检标本分离培养11株Hp菌株,通过随机扩增的DNA多态性分析确定菌株为不同来源.应用琼脂稀释法及E-TEST检测CLA与MZ对Hp的最低抑菌浓度(MIC).应用透射电镜法及青霉素结合蛋白(PBP)竞争性结合抑制实验探讨CLA对Hp的作用机制.结果 在11株不同来源的Hp菌株,1×MIC浓度的CLA可明显改善MZ耐药菌株的MIC值(1.442±0.459比0.376±0.288,P=0.0077),使MZ耐药菌株转变为敏感菌株.CLA可与Hp 30.5×103～33.5×103的PBP结合,使Hp发生球形变、空泡样变,细胞壁破裂及溶菌.结论 CLA在体外可降低Hp对MZ的耐药性,其机制可能与CIA结合PBP进而破坏Hp细胞壁有关.     

Prevalence of Helicobacter pylori resistance to clarithromycin and metronidazole determined by 23S ribosomal RNA and rdxA gene analyses in Hiroshima,Japan

BACKGROUND AND AIMS: Resistance to antibiotics in Helicobacter pylori is increasing and becoming a serious problem in eradication treatment of H. pylori. The prevalence of H. pylori infections that are resistant to clarithromycin, metronidazole, or both were determined in H. pylori isolates in Hiroshima, Japan. METHODS: Sixty Japanese patients with H. pylori infection were collected between 1999 and 2000. To detect the resistance to clarithromycin and metronidazole, mutations of the 23S ribosomal RNA (rRNA) and rdxA genes that are responsible for resistance in H. pylori, were examined by direct sequencing analysis. RESULTS: Resistance to clarithromycin and metronidazole was detected in 12 (20.0%) and nine (15.0%) of the patients, respectively. Dual resistance to clarithromycin and metronidazole was detected in five (8.3%) patients. CONCLUSION: These results indicate that the relatively high prevalence of the dual resistance in H. pylori isolates may need special attention and new therapeutic approaches in Japan.     

Aspirin increases susceptibility of Helicobacter pylori to metronidazole by augmenting endocellular concentrations of antimicrobials

AIM： To investigate the increasing the susceptibility pylon） to metronidazole. mechanisms of aspirin of Helicobacter pylori （H METHODS： Hpylori reference strain 26695 and two metronidazole-resistant isolates of H pylori were included in this study. Strains were incubated in Brucella broth with or without aspirin （1 mmol/L）. The rdxA gene of Hpylori was amplified by PCR and sequenced. The permeability of Hpylori to antimicrobials was determined by analyzing the endocellular radioactivity of the cells after incubated with [7-^3H]-tetracycline. The outer membrane proteins （OMPs） of Hpylori 26695 were depurated and analyzed by SDS-PAGE. The expression of 5 porins （hopA, hopB, hopC, hopD and hopE） and the putative RND efflux system （hefABC） of H pylori were analyzed using real-time quantitative PCR. RESULTS： The mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H pylori. However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin.The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and herA, hefB, hefC of H pylori did not change when treated with aspirin. CONCLUSION： Although aspirin increases the susceptibility of H pylori to metronidazole, it has no effect on the mutations of rdxA gene of Hpylori. Aspirin increases endocellular concentrations of antimicrobials probably by altering the OMP expression.     

Mechanism of metronidazole resistance in Helicobacter pylori

OBJECTIVE : Drug resistance to Helicobacter pylori is one of the most important reasons for the failure of anti‐H. pylori treatment. Metronidazole is a preferred drug for the elimination of H. pylori. However, using this drug alone can easily lead to resistance. The aim of the present study was to investigate the mechanism of metronidazole resistance in H. pylori. METHODS : International standard strain NCTC11639 was used. For the nitrate reduction test, four strains were used as positive controls, two strains of Bacillus coli and two strains of Vibrio cholerae. Metronidazole was used as tablets (0.2 g per tablet). The following techniques were used: (i) metronidazole used to apply selective pressure; (ii) sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS‐PAGE); (iii) nitrate reduction test; and (iv) test to detect the enzyme activities associated with 95 different substrates for Gram‐negative bacteria. RESULTS : As a result of the selective pressure of metronidazole, 20 H. pylori colonies survived; the bacteriostatic zones of these colonies were 0 mm in diameter, whereas the original NCTC11639 bacteriostatic zones were 25 mm in diameter. There was no significant difference seen among the 18 strains of drug‐resistant H. pylori and the original NCTC11639 strain protein electrophoresis strips. In the nitrate reduction test, both sensitive and resistant H. pylori all tested negative and the control strains of Bacillus coli and Vibrio cholerae tested positive. After the mutation of H. pylori from sensitive to resistant, the activities of enzymes associated with mono‐methyl succinate, succinic acid and D ‐alanine metabolism were decreased, and those associated with L ‐fucose and 6‐phosphate glucose metabolism were increased. CONCLUSIONS : The resistance of H. pylori to metronidazole is not related to nitroreductase. There may be no obvious changes in membrane protein in the drug‐resistant strain. The metronidazole resistance of H. pylori is associated with its metabolism and a change in enzyme activities.     

Time-series gene expression prof iles in AGS cells stimulated with Helicobacter pylori

AIM: To extend the knowledge of the dynamic interaction between Helicobacter pylori (H. pylori) and host mucosa. METHODS: A time-series cDNA microarray was performed in order to detect the temporal gene expression prof iles of human gastric epithelial adenocarcinoma cells infected with H. pylori. Six time points were selected to observe the changes in the model. A differential expression prof ile at each time point was obtained by comparing the microarray signal value with that of 0 h. Real-time polymerase ...     

应用基因分型技术研究幽门螺杆菌感染的家庭聚集现象

目的：探讨本地区Hp感染的可能途径。方法：采用聚合酶链反应－限制性片段长度多态性（PCR－RFLP）方法分析60个家庭133名伴有上消化道症状的儿童及其一级亲属唾液和胃粘膜中的Hp尿素酶(UreC)基因，通过比较两种限制性核内切酶Hha I与Alu I酶切复合类型（RFLP－C）评价儿童获得Hp的可能途径。结果：78个Hp阳性的家庭成员共确定22个Hp酶 型。25．0％（7／28）Hp阳性儿童从唾液中扩增出Hp，33．3％（10／30）Hp阳性的亲属从唾液中扩增出Hp,唾液与相应胃窦Hp的RFLP－C类型一致。83．9％（26／31）先证感染的Hp与其亲属感染的Hp与其亲属感染的Hp类型相同。结论：PCR－RFLP分析Hp Ure C基因的酶切类型分辨率较高，直接扩增样本Hp方法简便，可应用于Hp的流行病学研究。Hp感染患唾液与胃粘膜中扩增出的Hp Ure C基因RFLP－C酶切类型完全一致，同一家庭内感染的Hp Ure C基因RFLP类型高相符，提示家庭内成员的口一口传播可能是儿童期获得Hp的重要模式。     

Effect of Helicobacter pylori VacA on gene expression of gastric cancer cells

AIM: To determine the effect of Helicobacter pylori VacA on gene expression of gastric cancer cells. METHODS: Gene expression profile of a gastric cancer cell line, SGC7901, after challenged by VacA~+ and VacA~- H pylori broth culture supernatants (BCS), was detected by the cDNA microarray technique. Cytoskeleton changes of SGC7901 and HeLa cells were observed through high-resolution laser scanning confocal microscopy. RESULTS: A total of 16 000 cDNA clones were detected. The percentage of genes with heterogeneous expression in SGC7901 cells challenged by VacA~+ BCS reached 5%, compared with that challenged by VacA~- BCS. There were 865 genes/EST with 2-fold differential expression levels and 198 genes/EST with 3-fold differential expression levels. Most of these genes were involved in vital cell events including signal transduction, regulation of gene expression, cytoskeleton, apoptosis, stress response and inflammation, cell cycle and tumor development. Cells co-cultured with VacA~+ BCS showed collapsed and disrupted microtubular cytoarchitecture. CONCLUSION: VacA~+ BCS can disrupt cytoskeletal architecture, likely through affecting the expression of cytoskeleton-associated genes, directly induce the expression of tumor promoter-related genes and inhibit the expression of tumor suppressor genes, thus favoring the development of tumors. VacA~+ BCS can also alter the expression of inflammation and stress response genes. This suggests that VacA may play an important role in the pathogenicity of H pylori.