Evidence for a pentose phosphate pathway in Helicobacter pylori

Abstract Evidence for the presence of enzymes of the pentose phosphate pathway in Helicobacter pylori was obtained using ³¹P nuclear magnetic resonance spectroscopy. Activities of enzymes which are part of the oxidative and non-oxidative phases of the pathway were observed directly in incubations of bacterial lysates with pathway intermediates. Generation of NADPH and 6-phosphogluconate from NADP⁺ and glucose 6-phosphate indicated the presence of glucose 6-phosphate dehydrogenase and 6-phosphogluconolactonase. Reduction of NADP⁺ with production of ribulose 5-phosphate from 6-phosphogluconate revealed 6-phosphogluconate dehydrogenase activity. Phosphopentose isomerase and transketolase activities were observed in incubations containing ribulose 5-phosphate and xylulose 5-phosphate, respectively. The formation of erythrose 4-phosphate from xylulose 5-phosphate and ribose 5-phosphate suggested the presence of transaldolase. The activities of this enzyme and triosephosphate isomerase were observed directly in incubations of bacterial lysates with dihydroxyacetone phosphate and sedoheptulose 7-phosphate. Glucose-6-phosphate isomerase activity was measured in incubations with fructos 6-phosphate. The presence of these enzymes in H. pylori suggested the existence of a pentose phosphate pathway in the bacterium, possibly as a mechanism to provide NADPH for reductive biosynthesis and ribose 5-phosphate for synthesis of nucleic acids.     

pH-dependent binding of Helicobacter pylori to pig gastric mucins

A microtiter-based assay was developed to study the binding of Helicobacter pylori to pig gastric mucins purified by density-gradient centrifugation in CsCl/4 M guanidinium chloride. Binding of H. pylori was observed over the 'mucin' band as well as with 'low-density' components in the gradients, and binding to the latter was more pronounced when incubations were performed at 37 degrees C as compared to 20 degrees C. At a lower pH, binding of H. pylori (strain SVA 40) to the 'high-density' mucins from pig antrum was increased but binding to the 'low-density' ones was decreased. Binding of the P466 strain (Le(b)-specific) was mainly associated with the 'mucin' band, whereas the MO19 strain reacted preferentially with the 'low-density' components. In summary, H. pylori may bind to gastric mucins and the binding is influenced by temperature, pH and the repertoire of bacterial adhesins.     

Partial characterization of a cell-free hemolytic factor produced by Helicobacter pylori

Abstract Maximum cell-free hemolytic activity of Helicobacter pylori cultured in broth containing 10% horse serum occurred only after the stationary phase of growth was reached, unlike many hemolysins produced by Gram-negative bacteria which are active during exponential growth. This characteristic of the H. pylori hemolytic factor suggested that it might also possess protease activity. However, because no evidence of albumin degradation was found, the hemolysis by cell-free concentrates of H. pylori appears to be due to a unique factor derived from the organism. Because variable hemolysis results were obtained with culture broths lacking albumin or serum, these proteins may act as carriers or stabilizers of the putative hemolysin.     

Identification and characterization of binding properties of Helicobacter pylori by glycoconjugate arrays

The microaerophilic bacterium Helicobacter pylori is well established for its role in development of different gastric diseases. Bacterial adhesins and corresponding binding sites on the epithelial surface allow H. pylori to colonize the gastric tissue. In this investigation, the adhesion of H. pylori to dot blot arrays of natural glycoproteins and neoglycoproteins was studied. Adhesion was detected by overlay with fluorescence-labeled bacteria on immobilized (neo)glycoproteins. The results confirmed the interaction between the adhesin BabA and the H-1-, Lewis b-, and related fucose-containing antigens. In addition, H. pylori bound to terminal alpha2-3-linked sialic acids as previously described. The use of a sabA mutant and sialidase treatment of glycoconjugate arrays showed that the adherence of H. pylori to laminin is mediated by the sialic acid-binding adhesin, SabA. The adhesion to salivary mucin MUC5B is mainly associated with the BabA adhesin and to a lesser extent with the SabA adhesin. This agrees with reports, that MUC5B carries both fucosylated blood group antigens and alpha2-3-linked sialic acids. The adhesion of H. pylori to fibronectin and lactoferrin persisted in the babA/sabA double mutant. Because binding to these molecules was abolished by denaturation rather than by deglycosylation, it was suggested to depend on the recognition of unknown receptor moieties by an additional unknown bacterial surface component. The results demonstrate that the bacterial overlay method on glycoconjugate arrays is a useful tool for exploration and the characterization of unknown adhesin specificities of H. pylori and other bacteria.     

In vivo expression of the 25-kDa laminin-binding protein of Helicobacter pylori

The gastroduodenal pathogen Helicobacter pylori has been shown to inhibit the interaction between the extracellular matrix protein laminin and its receptor on gastric epithelial cells, potentially contributing to a loss of mucosal integrity. As a 25-kDa outer membrane protein of H. pylori in association with the bacterial lipopolysaccharides (LPS) mediates attachment to laminin, the aim of this study was to determine whether the 25-kDa protein is produced by H. pylori in infected hosts. We examined the immune response to the 25-kDa laminin binding protein in 12 paediatric patients; samples from a H. pylori-negative healthy adult were used as controls. In immunoblotting, antibodies to a 25-kDa protein were found in the serum and saliva of H. pylori-positive individuals only, and using the positive sera and saliva, laminin binding to the 25-kDa protein was inhibited. Thus, the 25-kDa laminin-binding protein is produced by H. pylori in infected hosts.     

幽门螺杆菌动物模型研究进展

幽门螺杆菌动物模型用于HP相关疾病和HP疫苗作用的研究。常规实验动物包括悉生猪、悉生狗、非人类灵长动物、猫、雪貂、小鼠、大鼠、沙鼠等。猫螺杆菌和雪貂螺杆菌感染也被用于模型研究。最近,转基因小鼠和基因敲除小鼠也被用作幽门螺杆菌动物模型研究。     

Genetic relationship among isolates of Helicobacter pylori: evidence for the existence of a Helicobacter pylori species-complex

We investigated the population genetics of 23 isolates of H. pylori by allozyme electrophoresis using 16 enzyme loci. Isolates were obtained from adult patients of whom 48% were of Greek extraction. Eight patients (35%) had an active duodenal ulcer. Allelic variation per loci ranged from 2 to 11 alleles. Four major genetic clusters were apparent, having >75% fixed genetic differences. There was no distinct clustering (clonal structure) on the basis of the geographical origin of the persons from whom isolates were obtained, indicating that this bacterium has not recently jumped a species barrier into humans. Isolates associated with ulcer disease were not monophyletic, with isolates from ulcer patients being found in phylogenetically diverse branches of the dendogram derived from the data. Based on the genetic diversity of H. pylori isolates, we propose that isolates should be classified as belonging not to a single species but to a `Helicobacter pylori species-complex'.     

非幽门螺杆菌：一类人兽共患病病原菌

过去的几十年,非幽门螺旋杆菌的研究迅速发展,他们不仅能感染和人类密切相关的动物,在人类的胃肠、肝胆及其他系统的疾病中也起着重要的作用,是一类人兽共患病病原菌。     

幽门螺杆菌空泡毒素研究进展

幽门螺杆菌空泡毒素是该菌产生的已知其它细菌毒素无明显源性的唯一蛋白毒素。该毒素是幽门螺杆菌重要的毒力致病因子,它的产生与感染胃肠上皮损伤和溃疡形成密切相关。本就幽门螺杆菌空泡毒素的结构与功能研究进展以及在未来免疫预防与免疫治疗中的作用进行了阐述。     

Studies on gangliosides with affinity for Helicobacter pylori: binding to natural and chemically modified structures

Helicobacter pylori, like many other microbes, has the ability to bind to carbohydrate epitopes. Several sugar sequences have been reported as active for the bacterium, including some neutral, sulfated, and sialylated structures. We investigated structural requirements for the sialic acid-dependent binding using a number of natural and chemically modified gangliosides. We have chosen for derivatization studies two kinds of binding-active glycolipids, the simple ganglioside S-3PG (Neu5Ac alpha 3Gal beta 4GlcNAc beta 3Gal beta 4Glc beta 1Cer, sialylparagloboside) and branched polyglycosylceramides (PGCs) of human origin. The modifications included oxidation of the sialic acid glycerol chain, reduction of the carboxyl group, amidation of the carboxyl group, and lactonization. Binding experiments confirmed a preference of H. pylori for 3-linked sialic acid and penultimate 4-linked galactose. As expected, neolacto gangliosides (with Gal beta 4GlcNAc in the core structure) were active in our assays, whereas gangliosides with lacto (Gal beta 3GlcNAc) and ganglio (Gal beta 3GalNAc) carbohydrate chains were not. Negative binding results were also obtained for disialylparagloboside (with terminal NeuAc alpha 8NeuAc) and NeuAc alpha 6-containing glycolipids. Chemical studies revealed dependence of the binding on Neu5Ac and its glycerol and carboxyl side chains. Most of the derivatizations performed on these groups abolished the binding; however, some of the amide forms turned out to be active, and one of them (octadecylamide) was found to be an excellent binder. The combined data from molecular dynamics simulations indicate that the binding-active configuration of the terminal disaccharide of S-3PG is with the sialic acid in the anticlinal conformation, whereas in branched PGCs the same structural element most likely assumes the synclinal presentation.     

Protection against Helicobacter pylori infection by intestinal immunisation with a 50/52-kDa subunit protein

A mouse model of Helicobacter pylori infection was used to evaluate the vaccine antigen potential of the citrate synthase homologue protein purified from the H. pylori NCTC 11637 strain. Mice were immunised with the protein by intra-Peyer's patch immunisation. This route gives maximal intestinal immunisation and was used to screen oral vaccine candidate antigens without the added complication of simultaneously testing oral delivery systems. Two weeks post-immunisation mice were infected with Sydney strain H. pylori and 4 weeks after infection the mice were killed and the level of H. pylori infection in the stomach determined. Pre-immunisation with the 50/52-kDa protein led to a 84-91% reduction in H. pylori infection compared to unimmunised controls.     

Inhibition of Helicobacter pylori haemogglutination activity by human salivary mucins

Abstract Thirty isolates of Helicobacter pylori from gastric biopsies agglutinated human erthyrocyte suspensions. Crude mucin preparation derived from saliva of 20 different donors were examined for their ability to inhibit haemagglutination. All mucin preparations exhibited strong inhibitory activity. Removal of sialic residues from mucin preparations by treatment with neuraminidase resulted in a substantial reduction of their inhibitory activity. The mucin prepations had no bactericidal or aggregation activity for H. pylori . These results are discussed in the context of the role of mucins in colonization of the gastric mucosa by H. pylori     

Comparison of two management strategies for Helicobacter pylori treatment: clinical study and cost-effectiveness analysis

BACKGROUND: First-line proton pump inhibitor-based triple and quadruple therapies for Helicobacter pylori eradication present similar levels of efficacy. Cross-over treatment (quadruple following triple failure, and triple following quadruple failure) seems the most sensible approach to treatment failures, but the two strategies -'quadruple first' versus 'triple first'- have not been previously compared. The aims of our study were to assess the usefulness and the cost-effectiveness of the two treatment strategies. MATERIAL AND METHODS: Forty-nine out of 344 patients included in a previous study comparing triple therapy - 7 days of omeprazole, amoxicillin and clarithromycin twice a day - with quadruple therapy - 7 days of omeprazole twice a day, plus tetracycline, metronidazole and bismuth subcitrate three times a day - failed initial treatment and were assigned to cross-over therapy. Cure was determined by urea breath test. A decision analysis was performed to compare the two eradication strategies. RESULTS: Intention to treat cure rates were 46% (10/22 patients; 95% CI 24-68%) for second-line triple therapy and 63% (17/27 patients; 95% CI 42-81%) for second-line quadruple therapy. Per protocol cure rates were 71% and 85%, respectively. Intention to treat cure rates were 87% (95% CI 81-92%) for the 'triple first' versus 86% (95% CI 80-91%) for the 'quadruple first' strategy (p = .87). The 'quadruple first' strategy was more cost-effective. The incremental cost of 'triple first' strategy per person was 19 in the low-cost area and 65 US dollars in the high-cost area. CONCLUSIONS: The effectiveness of 'triple first' and 'quadruple first' strategies is similar, although the latter seems slightly more cost-effective.     

Inhibition of binding of Helicobacter pylori to the glycolipid receptors by probiotic Lactobacillus reuteri

We examined the competition of binding of Lactobacillus reuteri and Helicobacter pylori to gangliotetraosylceramide (asialo-GM1) and sulfatide which are putative glycolipid receptor molecules of H. pylori, and identified a possible sulfatide-binding protein of the L. reuteri strain. Among nine L. reuteri strains, two (JCM1081 and TM105) were shown to bind to asialo-GM1 and sulfatide, and to inhibit binding of H. pylori to both glycolipids by a thin layer chromatogram-overlay assay using biotin-labeled bacterial cells. The extract from the bacterial cells of strain TM105 with several detergents, including octyl beta-D-glucopyranoside, retained binding to both glycolipids and also inhibited H. pylori binding, suggesting that a binding inhibitor(s) is associated with the bacterial cell surface. When the cell extract was applied to the agarose gel immobilized galactose 3-sulfate corresponding to the structure of sugar moieties of sulfatide, an approximately 47-kDa protein was found to bind to the gel. This observation strongly suggested that inhibition by selected L. reuteri strains help to prevent infection in an early stage of colonization in H. pylori and proposed that L. reuteri strains sharing glycolipid specificity with H. pylori have a potential as probiotics.     

Optimized conditions for the fermentation of Helicobacter pylori and production of vacuolating cytotoxin

Abstract We report here improvements to the growth media and fermentation conditions which result in a substantial increase of Helicobacter pylori growth and in the enhanced production of vacuolating cytotoxin. Addition of glucose to the medium resulted in the increase of cell yield, cell viability and a significant improvement in the production of vacuolating cytotoxin.     

Bioaccumulation of Amylose-Like Glycans by Helicobacter pylori

Background:  Helicobacter pylori cell surface is composed of lipopolysaccharides (LPSs) yielding structures homologous to mammalian Lewis O -chains blood group antigens. These structures are key mediators in the definition of host-microbial interactions and known to change their expression pattern in response to environmental pressure.
Aims:  The present work is focused on the identification of new H. pylori cell-surface glycosides. Special attention is further devoted to provide insights on the impact of in vitro subcultivation on H. pylori cell-surface phenotypes.
Methods:  Cell-surface glycans from H. pylori NCTC 11637 and two clinical isolates were recovered from the aqueous phase resulting from phenol:water extraction of intact bacteria. They were evaluated in relation to their sugars and glycosidic-linkages composition by CG-MS, size-exclusion chromatography, NMR, and Mass Spectrometry. H. pylori glycan profile was also monitored during subcultivation in vitro in agar and F12 liquid medium.
Results:  All three studied strains produce LPS expressing Lewis epitopes and express bioaccumulate amylose-like glycans. Bioaccumulation of amylose was found to be enhanced with the subcultivation of the bacterium on agar medium and accompanied by a decrease in the expression of LPS O -chains. In contrast, during exponential growth in F12 liquid medium, an opposite behavior is observed, that is, there is an increase in the overall amount of LPS and decrease in amylose content.
Conclusions:  This work shows that under specific environmental conditions, H. pylori expresses a phase-variable cell-surface α-(1→4)-glucose moiety.     

幽门螺杆菌感染诊断方法的比较

目的:考核各种H.pylori感染诊断方法,试图证明分离培养仍是细菌性感染诊断的最可靠方法.方法:315例胃十二指肠疾病患者同时进行胃活检组织分离培养,病理切片找菌,快速脲酶试验,14CO2呼气试验检查,比较它们之间的检出率差异.结果:四种方法各自的总检出率差异无显著性.以分离培养为金标准,其他方法的误诊误治率可达12.06%～22.22%.各种诊断方法对H.pylori感染的实际检出率差异存在着显著性.结论:本研究提示,分离培养应为H.pylori感染临床诊断的金标准.