Helicobacter pylori and gastric acid: biological and therapeutic implications

Parallel synthesis of potent, pyrazole-based inhibitors of Helicobacter pylori dihydroorotate dehydrogenase

The identification of several potent pyrazole-based inhibitors of bacterial dihydroorotate dehydrogenase (DHODase) via a directed parallel synthetic approach is described below. The initial pyrazole-containing lead compounds were optimized for potency against Helicobacter pylori DHODase. Using three successive focused libraries, inhibitors were rapidly identified with the following characteristics: K(i) < 10 nM against H. pylori DHODase, sub-microg/mL H. pylori minimum inhibitory concentration activity, low molecular weight, and >10 000-fold selectivity over human DHODase.

The long-term effects of cure of Helicobacter pylori infection on patients with atrophic body gastritis

BACKGROUND

Helicobacter pylori infection induces atrophic body gastritis, but the long-term effect of its cure on body atrophy is unclear.

AIM

To investigate the long-term effects of H. pylori cure on gastric morpho-functional parameters in patients with atrophic body gastritis.

METHODS

Forty patients with atrophic body gastritis were cured of H. pylori infection. Gastroscopy with biopsies, gastrin and pepsinogen I levels and basal and stimulated acid secretion were evaluated before and 6-12 months after treatment.

RESULTS

At eradication assessment (6-12 months), in eight of the 40 patients, body atrophy was no longer observed, whereas in 32 of the 40 it remained substantially unchanged (2.03 +/- 0.12 vs. 1.83 +/- 0.15). In the eight patients with reversed body atrophy, gastrinaemia decreased significantly with respect to pre-treatment values (265 +/- 59.9 pg/mL vs. 51.8. +/- 6.04 pg/mL), and basal and stimulated acid secretion increased significantly after cure. In the 32 patients still presenting body atrophy, gastrinaemia was similar topre-treatment values (457 +/- 76.04 pg/mL vs. 335.1 +/- 58.8 pg/mL). At follow-up (21-25 and 32-70 months), the eight patients with reversed body atrophy continued with normal gastrinaemia (35.3 +/- 10.1 pg/mL vs. 38.5 +/- 8.8 pg/mL), but in the 19 patients with continued atrophy, both corporal atrophy and intestinal metaplasia remained substantially unchanged.

CONCLUSIONS

Following successful treatment in patients with atrophic body gastritis and H. pylori infection, long-term histological investigations are crucial in order to detect reversed body damage or to confirm continued body atrophy.

Helicobacter pylori infection in diabetic patients: prevalence and endoscopic findings

BACKGROUND: In patients with diabetes mellitus, chronic infections are frequent and severe, due to the impairment of their immune status. However, data on the prevalence of Helicobacter pylori (H. pylori) infection in diabetics are scanty and contradictory. The aim of our study was to assess the prevalence of H. pylori infection in diabetic patients and to evaluate the association between endoscopic features and H. pylori colonization of the gastric mucosa in diabetes mellitus. METHODS: A cross-sectional study of 172 dyspeptic patients (67 diabetics and 105 nondiabetic subjects) was designed. In all cases, an upper gastrointestinal endoscopy was performed, gastroduodenal lesions were noted, and the presence of gastritis and H. pylori was assessed by histopathological examination. Differences between diabetic patients and nondiabetic subjects were evaluated. RESULTS: The difference of H. pylori prevalence between diabetics (37.3%) and nondiabetics (35.2%) was not significant (P=0.78). Nor did the prevalence of gastritis and peptic ulcer differ significantly between the two groups (59.7% vs. 49.5%, P=0.19; and 32.8% vs. 40.9%, P=0.08, respectively). Studying only H. pylori-positive patients, we found no difference between diabetics and nondiabetics with regard to the prevalence of either gastritis (80% vs. 72.9%, P=0.71) or peptic ulcer (91.8% vs. 76%, P=0.09). CONCLUSIONS: Our data do not support an association between H. pylori infection and diabetes mellitus. This is confirmed by the lack of difference between diabetics and nondiabetics with regard to the prevalence of both H. pylori infection and H. pylori-related gastroduodenal disorders.

The epidemic of esophageal adenocarcinoma

The incidence and mortality related to esophageal adenocarcinoma (EAC) have been increasing in the United States, several European countries, and Oceania for the past 2 to 3 decades. Survival remains dismal, with little improvement during the same time period. Variations in the coding, classification, and detection of gastroesophageal malignancy may have contributed partially to the observed trends. Remarkable differences related to gender, ethnicity, and geography characterize the epidemiology of EAC. Gastroesophageal reflux disease (GERD) is the main risk factor for Barrett's esophagus, which is the only known precursor lesion for EAC. Several risk factors that promote the development of GERD and/or Barrett's esophagus have been proposed to explain these rising trends; these factors include the declining rates of Helicobacter pylori infection, obesity, dietary factors, and certain drugs.

Energetics of Helicobacter pylori and its implications for the mechanism of urease-dependent acid tolerance at pH 1

In the presence of urea the neutrophilic human pathogen Helicobacter pylori survives for several hours at pH 1 with concomitant cytoplasmic pH homeostasis. To study this effect in detail, the transmembrane proton motive force and cytoplasmic urease activity of H. pylori were determined at various pH values. In the absence of urea, the organism maintained a close-to-neutral cytoplasm and an internally negative membrane potential at external pH values greater than 4 to 5. In the presence of urea, H. pylori accomplished cytoplasmic pH homeostasis down to an external pH of 1.2. At this external pH, the cytoplasmic pH was 4.9 and the membrane potential was slightly negative inside. The latter finding is in contrast to the situation in acidophiles, which develop inside-positive membrane potentials under similar conditions. Measurements of the time course of the membrane potential confirmed that addition of urea to the cells led to hyperpolarization. Most likely, this effect was due to electrogenic export of ammonium cations from the cytoplasm. The urease activity of intact cells increased nearly exponentially with decreasing external pH. This activation was not due to enhanced gene expression at low external pH values. In cell extracts the pH optimum of urease activity was dependent on the buffer system and was about pH 5 in sodium citrate buffer. Since this is the cytoplasmic pH of the cells at pH 1 to 2, we propose that cytoplasmic pH is a factor in the in vivo activation of the urease at low external pH values. The mechanism by which urease activity leads to cytoplasmic pH homeostasis in H. pylori is discussed.

Helicobacter pylori, parietal cell antibodies and autoimmune gastropathy in type 1 diabetes mellitus

BACKGROUND

Fifteen to 20% of type 1 diabetic patients exhibit parietal cell antibodies (PCA), which are associated with autoimmune gastritis, hypochlorhydria, iron deficiency and pernicious anaemia.

AIM

To examine whether Helicobacter pylori infection could explain the high prevalence of PCA and autoimmune gastropathy in diabetes. If so, H. pylori eradication could prevent autoimmune gastritis.

METHODS

In 229 type 1 diabetics (M/F: 135/94; age: 41 +/- 12 years) PCA were measured. H. pylori infection was assessed by serology, urea breath test in all and by histology (updated Sydney system) in 88 subjects. Pentagastrin tests were performed in 42 patients.

RESULTS

Sixty-nine patients were PCA-positive. H. pylori infection was present in 72 patients and was negatively associated with HLA-DQA1*0103-B1*0603 (OR=0.12, P=0.015) and positively with DQA1*0501-B1*0201 (OR=1.9, P=0.032). PCA-positivity was linked to HLA-DQA1*0501-B1*0301 (OR=3.9, P=0.017). A link between H. pylori and PCA was observed when PCA-positivity was defined as a titre > or = 1/20 (OR=2.0, P=0.03), but not if > or =1/40 was the cut-off point. PCA-positivity, but not H. pylori infection, was associated with iron deficiency anaemia (OR=2.7, P=0.008), pernicious anaemia (OR= 33.5, P < 0.0001), hypochlorhydria (OR=12.1, P=0.0008) and autoimmune gastritis (OR=12.5, P < 0.0001).

CONCLUSIONS

The HLA-bound susceptibility of H. pylori and PCA differed. PCA-positivity but not ongoing H. pylori infection is associated with autoimmune gastritis. Low titres of PCA might reflect H. pylori infection rather than autoimmune gastropathy.

Acid survival of Helicobacter pylori: how does urease activity trigger cytoplasmic pH homeostasis?

Helicobacter pylori can survive for several hours at pH 1 in the presence of urea. Under these conditions, the organism maintains its cytoplasmic pH at a value close to neutral. The role of the cytoplasmically located urease enzyme in this process is a matter of debate. We propose that cytoplasmic ammonia generated by the action of urease is protonated by H(+) ions leaking in from the acidic medium and that the NH(4)(+) formed is extruded from the cytoplasm via an as-yet-unidentified transport system. This mechanism is compared with the general mechanism of cytoplasmic pH homeostasis in microorganisms.

pathogenesis of Helicobacter pylori-induced gastric inflammation

Helicobacter pylori causes persistent inflammation in the human stomach, yet only a minority of persons harbouring this organism develop peptic ulcer disease or gastric malignancy. An important question is why such variation exists among colonized individuals. Recent evidence has demonstrated that H. pylori isolates possess substantial phenotypic and genotypic diversity, which may engender differential host inflammatory responses that influence clinical outcome. For example, H. pylori strains that possess the cag pathogenicity island induce more severe gastritis and augment the risk for developing peptic ulcer disease and distal gastric cancer. An alternative, but not exclusive, hypothesis is that enhanced inflammation and injury is a consequence of an inappropriate host immune response to the chronic presence of H. pylori within the gastric niche. Investigations that precisely delineate the mechanisms responsible for induction of gastritis will ultimately help to define which H. pylori-colonized persons bear the highest risk for subsequent development of clinical disease, and thus, enable physicians to focus eradication therapy.

Rapid molecular identification and subtyping of Helicobacter pylori by pyrosequencing of the 16S rDNA variable V1 and V3 regions

We describe here the use of real-time DNA sequence analysis of Helicobacter pylori 16S rRNA gene fragments by pyrosequencing for rapid molecular identification and subtyping of clinical isolates based on DNA sequence heterogeneity within the variable V1 and V3 regions. Six individual 16S rDNA V1 alleles (position 75-100) were identified in 23 clinical isolates obtained from gastric biopsy specimens. Eleven of these revealed sequence identities with H. pylori 26695 and one was identical with the rrn genes in strain J99. The other V1 alleles showing single or double nucleotide mutations or single nucleotide insertions could be divided into four groups with 5, 4, 1, and 1 isolates each. Two out of 25 isolates demonstrated single C to T transitions in the V3 region (position 990-1020). The present findings show that subtle DNA sequence variation occurs sufficiently often in the 16S rDNA variable V1 and V3 regions of H. pylori to provide a consistent system for subtyping.

Characterization of the low-pH responses of Helicobacter pylori using genomic DNA arrays

Helicobacter pylori is unique among bacterial pathogens in its ability to persist in the acidic environment of the human stomach. To identify H. pylori genes responsive to low pH, the authors assembled a high-density array of PCR-amplified random genomic DNA. Hybridization of radiolabelled cDNA probes, prepared using total RNA from bacteria exposed to buffer at either pH 4.0 or pH 7.0, allowed both qualitative and quantitative information on differential gene expression to be obtained. A previously described low-pH-induced gene, cagA, was identified together with several novel genes that may have relevance to the survival and persistence of H. pylori in the gastric environment. These include genes encoding enzymes involved in LPS and phospholipid synthesis and secF, encoding a component of the protein export machinery. A hypothetical protein unique to H. pylori (HP0681) was also found to be acid induced. Genes down-regulated at pH 4.0 include those encoding a sugar nucleotide biosynthesis protein, a flagellar protein and an outer-membrane protein. Differential gene expression was confirmed by total RNA slot-blot hybridization.

Disinfectant activity against different morphological forms of Helicobacter pylori: first results

The pathogenic bacterium Helicobacter pylori, which has infected more than one-half of the world's human population, exists in two morphological forms; the viable helical form and the disputed viable-but-not-culturable coccoid form. Infection by the helical form proceeds through the oral-oral route, while that by the coccoid form, if possible at all, is by the faecal-oral and/or the oral-oral route. The present pilot study addresses the question of disinfectant efficacy against both forms of the bacterium.

Differential gene expression from two transcriptional units in the cag pathogenicity island of Helicobacter pylori

Infection with Helicobacter pylori strains containing the cag Pathogenicity Island (cag PAI) is strongly correlated with the development of severe gastric disease, including gastric and duodenal ulceration, mucosa-associated lymphoid tissue lymphoma, and gastric carcinoma. Although in vitro studies have demonstrated that the expression of genes within the cag PAI leads to the activation of a strong host inflammatory response, the functions of most cag gene products and how they work in concert to promote an immunological response are unknown. We developed a transcriptional reporter that utilizes urease activity and in which nine putative regulatory sequences from the cag PAI were fused to the H. pylori ureB gene. These fusions were introduced in single copies onto the H. pylori chromosome without disruption of the cag PAI. Our analysis indicated that while each regulatory region confers a reproducible amount of promoter activity under laboratory conditions, they differ widely in levels of expression. Transcription initiating upstream of cag15 and upstream of cag21 is induced when the respective fusion strains are cocultured with an epithelial cell monolayer. Results of mouse colonization experiments with an H. pylori strain carrying the cag15-ureB fusion suggested that this putative regulatory region appears to be induced in vivo, demonstrating the importance of the urease reporter as a significant development toward identifying in vivo-induced gene expression in H. pylori.

Gastro-oesophageal reflux and duodenogastric reflux before and after eradication in Helicobacter pylori gastritis

OBJECTIVE

Helicobacter pylori and duodenogastric reflux (DGR) are both associated with chronic gastritis, peptic ulcer and gastric cancer. The nature of their interrelationship remains unclear. H. pylori eradication has also been reported to result in new or worsening acid gastro-oesophageal reflux (GOR). The aim of this study was to investigate the relationship between GOR, DGR and H. pylori infection.

METHOD

25 patients with H. pylori gastritis underwent ambulatory 24-hour oesophageal and gastric pHmetry and gastric bilirubin monitoring before and 12 weeks after H. pylori eradication, confirmed by 14C urea breath testing (UBT). Ten healthy subjects served as a control group.

RESULTS

There were no differences between patient and control groups for gastric alkaline exposure or gastric bilirubin exposure (P> 0.25 in all categories). Oesophageal acid reflux was higher in the study group (P< 0.02). No differences were detected in oesophageal acid reflux, gastric alkaline exposure, or gastric bilirubin exposure (P = 0.35, 0.18 and 0.11, respectively) before and after eradication.

CONCLUSIONS

Acid GOR is not increased by H. pylori eradication. DGR in patients with H. pylori gastritis is similar to that in healthy, non-infected subjects. H. pylori eradication produces no change in GOR or DGR. In patients with chronic gastritis, H. pylori infection and DGR appear to be independent of each other.

Helicobacter pylori infection and serum ferritin: A population-based study among 1806 adults in Germany

OBJECTIVE

Helicobacter pylori may possibly affect the iron metabolism by occult bleeding, impaired absorption of non-hem iron, and by scavenging hem iron or ferritin, as some studies have suggested. The aim of this study was to analyze the association between H. pylori infection and serum ferritin, a marker of the body iron stores. In this analysis, we paid particular attention to the role of dietary iron intake and CagA, an established virulence factor of the agent.

METHODS

The analysis is based on a cross-sectional national health and nutrition survey among healthy people in Germany conducted in 1987/1988. The examination included a detailed questionnaire on medical history and lifestyle factors, a 7-day food record, and blood samples. Infection with H. pylori was measured serologically by ELISA and Westernblot.

RESULTS

In total, 39.2% of 1806 persons aged 18 to 89 yr included in the study were H. pylori positive, of whom 57.6% had an infection with a CagA-positive H. pylori strain. Age- and sex-adjusted geometric mean of ferritin was 54.5 microg/dl among H. pylori-infected compared with 63.8 microg/dl among uninfected persons. A multiple linear regression model with log-transformed serum ferritin concentration as dependent variable and H. pylori infection and several potential confounding factors as independent variable was fitted. In this model, H. pylori infection was associated with a 17.0% decrease of the serum ferritin concentration (95% CI = 9.8-23.6). The association between H. pylori infection and serum ferritin levels did not vary by gender, age, and iron intake, and it was similar for CagA-positive and CagA-negative H. pylori infections.

CONCLUSIONS

The decreased serum ferritin concentration among subjects infected with H. pylori might be induced by the uptake of ferritin in the stomach by H. pylori. Possible health implications of H. pylori-induced low ferritin levels warrant further investigation.

Identification of genes regulated by prolonged acid exposure in Helicobacter pylori

To investigate the influence of prolonged acid exposure on the gene expression, transcripts of Helicobacter pylori, grown under pH 5.5 and pH 7.4 for five successive passages, were analysed by differential display PCR. Eight genes were regulated by prolonged acid exposure. These genes included topA, tufB, ureB, flaA, atoE in the H. pylori genome and a cDNA fragment with 54% identity of the predicted amino acid sequence to a Bacillus cereus YkoW protein. The remaining two cDNA fragments had no significant homology to known sequences. Our data suggest that most of these genes might be required for the resistance of H. pylori to prolonged acid exposure.

In vitro binding of Helicobacter pylori to monohexosylceramides

H. pylori is the major cause of human gastritis, duodenal ulcer and thus gastric adenocarcinoma. Many glycosphingolipid species have been postulated as receptors for H. pylori and it is likely that H. pylori attachment requires multiple, perhaps sequential receptor/ligand interactions. In this study, the binding of a number of H. pylori clinical isolates, as well as stock strains, to acid and neutral glycosphingolipids separated on thin-layer chromatograms was characterized under microaerobic conditions. All H. pylori clinical isolates, laboratory strains and type culture collection strains recognized galactosylceramide (Galbeta1Cer) with ceramide containing sphingosine and hydroxylated fatty acid (type I), or non-hydroxylated fatty acid (type II), on thin-layer chromatograms and when incorporated into liposomes. The clinical isolates bound stronger to Galbeta1Cer (type II) than Galbeta1Cer (type I) on TLC, whereas lab and culture collection strains showed the opposite binding preference. A clear preference in binding to Galbeta1Cer (type I) incorporated into liposome was shown by most tested strains. Clinical isolates bound well to glucosylceramide (Glcbeta1Cer) with hydroxylated fatty acid, whereas weak binding to this glycolipid was detected with the lab and type collection strains. None of the tested strains bound Glcbeta1Cer with non-hydroxylated fatty acid on the solid surface, but some strains of both clinical or type collection origins showed weak or very weak binding in the liposome assay. A clear distinction between the binding specificity of living organisms (under microaerobic conditions) as opposed to dying organisms (under normoxic conditions) illustrates the importance of cellular physiology in this process. These studies illustrate lipid modulation of the potential receptor function of monohexosylceramides and the distinction between the receptor repertoire of H. pylori clinical isolates and cultured strains commonly used to study host-cell adhesion.

Helicobacter pylori infection in the cat: evaluation of gastric colonization, inflammation and function

BACKGROUND

Further elucidation of the consequences of Helicobacter pylori infection on gastric mucosal inflammation and gastric secretory function would be facilitated by an animal model that is susceptible to infection with H. pylori, is broadly similar in gastric physiology and pathology to people, and is amenable to repeated non-invasive evaluation. The goal of this study was to examine the interrelationship of bacterial colonization, mucosal inflammation and gastric secretory function in cats with naturally acquired H. pylori infection.

MATERIALS AND METHODS

Twenty clinically healthy cats with naturally acquired H. pylori infection (cagA-, picB) and 19 Helicobacter-free cats were evaluated. Gastric colonization was determined by tissue urease activity, light microscopy, culture and PCR. The mucosal inflammatory response was evaluated by light microscopy, and by RT-PCR of the pro-inflammatory cytokines IL-1alpha, IL-1beta, IL-8 and TNF-alpha in gastric mucosa. Gastric secretory function was assessed by measuring pentagastrin-stimulated acid secretion, fasting plasma gastrin, and antral mucosal gastrin and somatostatin immunoreactivity.

RESULTS

H. pylori colonized the pylorus, fundus and cardia in similar density. Bacteria were observed free in the lumen of gastric glands and were also tightly adherent to epithelial cells where they were associated with microvillus effacement. Mononuclear inflammation, lymphoid follicle hyperplasia, atrophy and fibrosis were observed primarily in H. pylori-infected cats, with the pylorus most severely affected. Neutrophilic and eosinophilic infiltrates, epithelial dysplasia, and up-regulation of mucosal IL-1beta and IL-8 were observed solely in infected cats. Fasting plasma gastrin concentrations and pentagastrin-stimulated acid output were similar in both infected and uninfected cats. There was no relationship of bacterial colonization density or gastric inflammation to plasma gastrin concentrations or gastric acid output.

CONCLUSIONS

The pattern of colonization and the mucosal inflammatory response in cats with naturally acquired H. pylori are broadly similar to those in infected people, particularly children, and non-human primates. The upregulation of IL-8 in infected cats was independent of cagA and picB. Our findings argue against a direct acid-suppressing effect of H. pylori on the gastric secretory-axis in chronically infected cats.

Prolonged survival and cytoplasmic pH homeostasis of Helicobacter pylori at pH 1

In the presence of urea, Helicobacter pylori survived for at least 3 h at pH 1. Under these conditions, the cells maintained their cytoplasmic pH at 5.8. De novo protein synthesis during acid shock was not essential for survival of H. pylori at pH 1.

Associations of food-cobalamin malabsorption with ethnic origin, age, Helicobacter pylori infection, and serum markers of gastritis

OBJECTIVES

Food-cobalamin malabsorption is common in patients with low cobalamin levels. However, characterization of affected subjects has been limited. The aim of this study was to analyze demographic and gastric data in a large study population.

METHODS

Data were collected prospectively in 202 subjects (43 volunteers and 159 patients) who underwent the egg yolk-cobalamin absorption test (EYCAT). H. pylori status was determined in 167 of the subjects, serum gastrin and antiparietal cell antibody in 158 and pepsinogen (PG) I and PG II levels in 133.

RESULTS

Latin American and black patients had lower EYCAT results than did white or Asian-American ones (p = 0.0001) and had severe food-cobalamin malabsorption (EYCAT < 1%) more often (p = 0.0001). Age correlated inversely with EYCAT results (p = 0.02). H. pylori infection was associated with food-cobalamin malabsorption (p = 0.0001), especially with severe malabsorption where 29/37 subjects (78.4%) were infected. Malabsorption was also associated with higher gastrin levels (p = 0.0001) and lower PG I levels (p = 0.01) and PG I:PG II ratios (p = 0.0001). Multivariate analysis showed that ethnic origin, gastrin levels, H. pylori infection and, to a lesser extent, age were independently associated with the EYCAT results.

CONCLUSIONS

Latin American and black patients have food-cobalamin malabsorption more often than do white and Asian-American patients. This association is independent of the malabsorption's association with H. pylori infection, markers of gastritis, such as gastrin, and older age. The patterns of gastric tests suggest that malabsorption may be due to diverse mechanisms, not just atrophic gastritis. The possible role of H. pylori infection in many cases of severe food-cobalamin malabsorption also suggests avenues of treatment and prevention.

Eradication of Helicobacter pylori has no effect on gastric acidity in duodenal ulcer patients--evaluation of 24-h pH monitoring

It is accepted that eradication of Helicobacter pylori leads to healing of chronic active gastritis facilitates ulcer healing and prevents ulcer recurrence in duodenal ulcer (DU) patients. However, it is not entirely known whether the eradication of the bacteria normalizes gastric acid secretion and abolishes dyspeptic symptoms after ulcer healing. This study was aimed to evaluate the intragastric acidity and dyspeptic complaints before, and 3 months after, eradication in 18 endoscopically proven H. pylori positive DU patients. Gastric pH was measured by 24-h continuous intraluminal recording, serum gastrin measurements and Congo-red tests were also performed. Dyspeptic complaints and antacid consumptions were recorded in diary cards, antisecretory therapy was not allowed after the cessation of eradication therapy. Endoscopy, H. pylori status and Congo-red tests were controlled at the 6th and 12th week, while pH measurements and serum gastrin tests were performed at inclusion and 3 months later. Three patients dropped out and in 14 out of the remaining subjects healing of DUs and successful eradication was achieved by the 6th and 12th week controls. The 24-h median pH and the percentage of 24-h pH readings under pH 3 were not changing significantly by the 3-month controls (from 1.9+/-0.5 to 1.8+/-0.4 and from 52.6+/-5.5% to 58.6+/-5%, respectively). Similarly, no significant changes were observed in serum gastrin levels and dyspeptic symptom scores (from 72+/-7 pg/ml to 56.7+/-8 pg/ml and from 2.69+/-0.4 to 1.26+/-0.3, respectively). The antacid consumption was almost stable when compared with the pre- and post-eradication periods. It was concluded that despite successful H. pylori eradication and healing of DU, intragastric acidity does not change significantly at least 3 months after the therapy. The persisting dyspeptic symptoms and the need for antacid consumption suggest that some healed ulcer patients require antisecretory therapy in the post-eradication period.

Gastric-juice ammonia assay for diagnosis of Helicobacter pylori infection and the relationship of ammonia concentration to gastritis severity

OBJECTIVES

To determine the test characteristics of gastric-juice ammonia concentration as measured by an ion-selective electrode and a rapid ammonia detection device for the diagnosis of Helicobacter pylori infection and to assess the relationship between gastric-juice ammonia concentration and the severity of gastritis.

METHODS

Patients undergoing upper endoscopy had collection of gastric juice that was tested for ammonia using an ion-selective electrode and a rapid ammonia assay device that uses a pH-indicating membrane. A receiver operating characteristic curve was calculated for ammonia concentration. Severity of gastritis was graded using the Sydney classification (1) and correlated to gastric-juice ammonia concentration. Patients also underwent H. pylori testing by IgG serology, rapid urease testing, and histological special stain. Ammonia testing results were compared with a reference standard of two of three positive tests and with a second reference standard of a positive serology.

RESULTS

73 patients underwent endoscopy and collection of gastric juice. The receiver operating characteristic curve indicated an optimal cutoff value of 5 mM, yielding a sensitivity of 67%, specificity of 93%, positive predictive value of 67%, and negative predictive value of 93% (compared with the combined reference standard). The rapid NH3-testing device yielded a sensitivity of 83%, specificity 63%, positive predictive value 31%, and negative predictive value 95%. The severity of neutrophilic (p = 0.001) and mononuclear cell (p = 0.003) infiltration were significantly correlated with gastric-juice ammonia concentration.

CONCLUSIONS

Measurement of gastric-juice ammonia concentration by ion-selective electrode or rapid detection device is a relatively insensitive and nonspecific means of H. pylori diagnosis. Gastritis severity increases with gastric-juice ammonia concentration.

Helicobacter pylori-selective antibacterials based on inhibition of pyrimidine biosynthesis

We report the discovery of a class of pyrazole-based compounds that are potent inhibitors of the dihydroorotate dehydrogenase of Helicobacter pylori but that do not inhibit the cognate enzymes from Gram-positive bacteria or humans. In culture these compounds inhibit the growth of H. pylori selectively, showing no effect on other Gram-negative or Gram-positive bacteria or human cell lines. These compounds represent the first examples of H. pylori-specific antibacterial agents. Cellular activity within this structural class appears to be due to dihydroorotate dehydrogenase inhibition. Minor structural changes that abrogate in vitro inhibition of the enzyme likewise eliminate cellular activity. Furthermore, the minimum inhibitory concentrations of these compounds increase upon addition of orotate to the culture medium in a concentration-dependent manner, consistent with dihydroorotate dehydrogenase inhibition as the mechanism of cellular inhibition. The data presented here suggest that targeted inhibition of de novo pyrimidine biosynthesis may be a valuable mechanism for the development of antimicrobial agents selective for H. pylori.

Transcriptional analysis of major heat shock genes of Helicobacter pylori

The transcriptional organization and heat inducibility of the major heat shock genes hrcA, dnaK, dnaJ, groEL, and htpG were analyzed on the transcriptional level in Helicobacter pylori strain 69A. The strongly heat-induced dnaK operon was found to be tricistronic, consisting of the genes hrcA, grpE, and dnaK. The dnaJ gene specified one monocistronic mRNA which was also heat inducible. The genes groES and groEL were transcribed as one strongly heat-inducible bicistronic mRNA which exhibited exactly the same induction kinetic as the dnaK operon. Surprisingly, transcription of the monocistronic htpG gene was switched off after heat shock. The data presented are discussed with regard to the different mechanisms regulating expression of heat shock genes in H. pylori

Intercellular communication in Helicobacter pylori: luxS is essential for the production of an extracellular signaling molecule

Individual bacteria of numerous species can communicate and coordinate their actions via the production, release, and detection of extracellular signaling molecules. In this study, we used the Vibrio harveyi luminescence bioassay to determine whether Helicobacter pylori produces such a factor. Cell-free conditioned media from H. pylori strains 60190 and 26695 each induced >100-fold-greater luminescence in V. harveyi than did sterile culture medium. The H. pylori signaling molecule had a molecular mass of <10 kDa, and its activity was unaffected by heating to 80 degrees C for 5 min or protease treatment. The genome sequence of H. pylori 26695 does not contain any gene predicted to encode an acyl homoserine lactone synthase but does contain an orthologue of luxS, which is required for production of autoinducer-2 (AI-2) in V. harveyi. To evaluate the role of luxS in H. pylori, we constructed luxS null mutants derived from H. pylori 60190 and 26695. Conditioned media from the wild-type H. pylori strains induced >100-fold-greater luminescence in the V. harveyi bioassay than did conditioned medium from either mutant strain. Production of the signaling molecule was restored in an H. pylori luxS null mutant strain by complementation with a single intact copy of luxS placed in a heterologous site on the chromosome. In addition, Escherichia coli DH5alpha produced autoinducer activity following the introduction of an intact copy of luxS from H. pylori. Production of the signaling molecule by H. pylori was growth phase dependent, with maximal production occurring in the mid-exponential phase of growth. Transcription of H. pylori vacA also was growth phase dependent, but this phenomenon was not dependent on luxS activity. These data indicate that H. pylori produces an extracellular signaling molecule related to AI-2 from V. harveyi. We speculate that this signaling molecule may play a role in regulating H. pylori gene expression.

Influence of age on the steady state disposition of drugs commonly used for the eradication of Helicobacter pylori

BACKGROUND

The success of eradication therapy for Helicobacter pylori might be affected by the age of patients.

AIM

To investigate whether disposition of drugs commonly used for H. pylori eradication is age-dependent.

METHODS

Trough steady state serum levels of lansoprazole or ranitidine, amoxycillin, clarithromycin and metronidazole were monitored in 232 patients during the last dosing interval of a 5-day quadruple H. pylori eradication regimen. Detailed pharmacokinetic analysis was performed in 28 patients.

RESULTS

Linear correlations between age and trough serum levels were observed with lansoprazole (r=0.25; P=0.002), ranitidine (r=0. 38; P=0.001) and clarithromycin (r=0.36; P < 0.0001). These associations were also inversely dependent of creatinine clearance for ranitidine (r=0.36; P=0.001) and clarithromycin (r=0.30; P < 0. 0001). Multiple linear regression revealed age as an important factor influencing trough serum levels of lansoprazole, clarithromycin and ranitidine. There were significant inverse relationships between creatinine clearance and area under curve of ranitidine (r=0.88; P < 0.0001) and amoxycillin (r=0.56; P=0.002). Multiple linear regression revealed serum creatinine as the most important factor influencing the area under curve of ranitidine, clarithromycin and amoxycillin.

CONCLUSIONS

Age per se has little influence on pharmacokinetics of amoxycillin and ranitidine, which depend more on age-dependent decline in renal function. The influence of age, but not renal function was established for lansoprazole. Age and renal function have independent impacts on clarithromycin disposition.

Cure of Helicobacter pylori infection in atrophic body gastritis patients does not improve mucosal atrophy but reduces hypergastrinemia and its related effects on body ECL-cell hyperplasia

BACKGROUND

The effects of H. pylori eradication on atrophic body gastritis are controversial.

AIM

To investigate the effect of triple therapy on atrophic body gastritis in H. pylori-positive patients and its effect on morpho-functional gastric parameters.

METHODS

Thirty-five consecutive atrophic body gastritis patients with histological/serological evidence of H. pylori infection were treated. Before and 6 and 12 months after H. pylori eradication the patients were evaluated for fasting gastrinemia and pepsinogen I, basal and peak acid output, and detailed histological assessment including the ECL cell proliferative patterns.

RESULTS

Six months after treatment, 25 out of 32 patients were cured (78%). Cure of infection was associated with improvement in both basal (basal acid output mean 0.23 +/- 0.14 mmol/h vs. 1.75 +/- 0.7 mmol/h, P < 0.005) and stimulated acid secretion (peak acid output mean 3.0 +/- 1.06 mmol/h vs. 16.6 +/- 4.1 mmol/h, P=0.0017) as well as with reduction in hypergastrinemia (mean gastrin levels 444.1 +/- 110.7 pg/mL vs. 85.3. +/- 28 pg/mL; P < 0.005). In contrast, the eradication had no effect on body corporal atrophy and intestinal metaplasia, or pepsinogen I levels (mean 16.6 +/- 2.9 ng/mL vs. 14.2 +/- 2.1 ng/mL, N.S.). These results were confirmed at 12 months after eradication. A statistical inverse correlation was obtained (r=-0.3635, P < 0.05) between the corporal chronic infiltrate score and peak acid output values. A total of 53% of atrophic body gastritis patients showed a regression in severity of body ECL cell hyperplastic change.

CONCLUSION

Cure of H. pylori infection in patients with atrophic gastritis reverses some adverse effects on gastric function and ECL cell hyperplasia. H. pylori infection may be cured in atrophic body gastritis patients with partial reversion of its negative consequences on acid secretion and body ECL cell hyperplasia.

Morphological changes of the human gastric mucosa under long-term proton pump inhibitor therapy and their clinical relevance

Proton pump inhibitors are potent drugs for the treatment of acid-related diseases. The moderate hypergastrinaemia observed during therapy is a physiological response to low intragastric pH and the increase is limited to the first months of therapy with no further changes thereafter. Reports on endocrine cell changes in the antral mucosa under chronic PPI therapy are controversial and lack clinical relevance. In contrast, in the oxyntic mucosa hyperplastic argyrophil cell changes have been reported, dependent on the degree and duration of hypergastrinaemia, the severity of oxyntic mucosal gastritis, especially atrophy, and the presence of H. pylori infection. Current data do not support a progression from hyperplastic to dysplastic argyrophil cell lesions in humans in the absence of additional genetic factors. Data on the progression of oxyntic gastritis under chronic PPI treatment in comparison to untreated controls could not be confirmed in more recent studies including a well-matched control population. The main factor for gastritis progression is the presence of Helicobacter pylori infection. The bacterium not only causes a chronic inflammation of the gastric mucosa, resulting in atrophy and intestinal metaplasia, but also influences endocrine cell populations involved in the regulation of gastric acid secretion. The clinical benefit of H. pylori eradication in reflux esophagitis patients is still a matter of debate. The complex relations in humans between hypergastrinaemia, (oxyntic) gastritis and atrophy, H. pylori infection, argyrophil cell hyperplasia, and the effects of long-term PPI treatment of acid-related diseases do not allow a quantification of the contribution of each single factor for the observed changes.

Pharmacokinetic considerations in the eradication of Helicobacter pylori

As Helicobacter pylori plays an important role in the aetiopathogenesis of peptic ulcer, therapeutic strategies aimed at maintaining long term remission have shifted from the control of intragastric pH to targeting H. pylori. According to recent international guidelines the clinical goals--rapid ulcer healing and prevention of relapse--can be best accomplished by combination therapy consisting of an antisecretory drug (proton pump inhibitor or ranitidine) and 2 antimicrobial agents (preferable amoxicillin, clarithromycin or metronidazole). When applying such multidrug regimens, possible synergy between the agents suggests that pharmacokinetic considerations might help to improve H. pylori eradication rates, which should be above 85 to 90% on an intention-to-treat basis. The present review summarises the pharmacokinetic properties and interaction potential of all drugs presently used in the various H. pylori eradication regimens, with emphasis on particular patient populations such as the elderly and those with renal impairment. The drugs considered are omeprazole, lansoprazole, pantoprazole, rabeprazole, ranitidine and ranitidine bismutrex, bismuth salts, amoxicillin, clarithromycin, azithromycin, roxithromycin, metronidazole, tinidazole and tetracycline. When addressing the clinically important questions of the efficacy, safety and costs of the recommended regimens, the impact of drug disposition on H. pylori eradication should not be neglected.

Negative association between Helicobacter pylori infection and reflux esophagitis in older patients: case-control study in Japan

BACKGROUND

Recent studies have clarified a close association between H. pylori infection and gastritis, peptic ulcer disease, and gastric cancer, but there is little information concerning the relationship between H. pylori infection and reflux esophagitis (RE). We investigated the relationship between H. pylori, RE, and corpus gastritis.

SUBJECTS AND METHODS

Ninety-five patients with RE and 190 sex- and age-matched asymptomatic healthy controls demonstrating no localized lesions in the upper GI tract were studied and evaluated for H. pylori infection, histologic gastritis, serum gastrin, and pepsinogens (PGs).

RESULTS

H. pylori infection was significantly lower in RE patients than in asymptomatic controls (41% vs. 76%, p <.01). Histologic gastritis of both the antrum and corpus was significantly less frequent (antrum; p <.01, corpus; p <. 01), and serum levels of PGI and the PG I/II ratio were significantly higher in RE patients than in controls (PGI; p <.05, PG I/II ratio; p <.01). When the subjects were divided into two age groups (59 years of age and younger and 60 years of age and older), a significant difference was found only among patients over 60 years of age (29% vs. 85%, p <.01). Among subjects in this age group, gastritis in both the antrum and corpus were significantly milder in RE patients than in controls. Although the prevalence of H. pylori infection was similar between the two groups of patients under 59 years of age, corpus gastritis was significantly milder in patients than in controls (p <.05).

CONCLUSIONS

A significantly low prevalence of H. pylori infection was found in RE patients over 60 years of age but not in those under 59 in comparison with sex- and age-matched controls. The relative lack of corpus gastritis might play a role in the pathogenesis of RE in our population through preservation of the acid secretion area.

Helicobacter pylori activates the histidine decarboxylase promoter through a mitogen-activated protein kinase pathway independent of pathogenicity island-encoded virulence factors

Helicobacter pylori infection of the gastric mucosa is accompanied by an activated histamine metabolism. Histamine plays a central role in the regulation of gastric acid secretion and is involved in the pathogenesis of gastroduodenal ulcerations. Histidine decarboxylase (HDC) is the rate-limiting enzyme for histamine production, and its activity is regulated through transcriptional mechanisms. The present study investigated the effect of H. pylori infection on the transcriptional activity of the human HDC (hHDC) promoter in a gastric epithelial cell line (AGS) and analyzed the underlying molecular mechanisms. Our studies demonstrate that H. pylori infection potently transactivated the hHDC promoter. The H. pylori-responsive element of the hHDC gene was mapped to the sequence +1 to +27 base pairs, which shows no homology to known cis-acting elements and also functions as a gastrin-responsive element. H. pylori regulates the activity of this element via a Raf-1/MEK/ERK pathway, which was activated in a Ras-independent manner. Furthermore, we found that H. pylori-induced transactivation of the hHDC promoter was independent of the cag pathogenicity island and the vacuolating cytotoxin A gene and therefore may be exerted through (a) new virulence factor(s). A better understanding of H. pylori-directed hHDC transcription can provide novel insights into the molecular mechanisms of H. pylori-dependent gene regulation in gastric epithelial cells and may lead to new therapeutic approaches.

Helicobacter felis infection is associated with lymphoid follicular hyperplasia and mild gastritis but normal gastric secretory function in cats

The relationship of Helicobacter felis, a bacterium observed in the stomachs of cats, to gastric disease is unclear. The objective of this study was to determine if H. felis infection alters gastric histopathology, proinflammatory cytokine expression, and secretory function and evokes a humoral immune response in cats. Five specific-pathogen-free (SPF) Helicobacter-free cats were studied before and for 1 year after oral inoculation with H. felis (ATCC 49179). Four SPF H. felis-uninfected cats served as controls. The stomachs of all five H. felis-inoculated cats became colonized, as determined by urease activity, histopathology, PCR, culture, and transmission electron microscopy of serial gastric biopsies at 0, 3, 5, 8, and 12 months. Uninoculated cats remained Helicobacter free. Lymphoid follicular hyperplasia, atrophy, and fibrosis were observed primarily in the pylorus of infected cats. Mild mononuclear inflammation was detected in both infected and uninfected cats, but was more extensive in infected cats, with pangastric inflammation, eosinophilic infiltrates, and cardia gastritis observed only in infected cats. No upregulation of antral mucosal interleukin 1alpha (IL-1alpha), IL-1beta, or tumor necrosis factor alpha was detected by reverse transcription-PCR in any cat. The gastric secretory axes, assessed by fasting plasma gastrin, antral mucosal gastrin and somatostatin immunoreactivity, and pentagastrin-stimulated gastric acid secretion, were similar in both infected and uninfected cats. Gradual seroconversion (immunoglobulin G) was observed in four of five infected cats, with enzyme-linked immunosorbent assay values reaching 4x to 12x baseline 12 months postinfection. These findings indicate that H. felis infection in cats induces lymphoid follicular hyperplasia, mild gastritis, and seroconversion, but is associated with normal gastric secretory function.

A H+-gated urea channel: the link between Helicobacter pylori urease and gastric colonization

Acidic media trigger cytoplasmic urease activity of the unique human gastric pathogen Helicobacter pylori. Deletion of ureI prevents this activation of cytoplasmic urease that is essential for bacterial acid resistance. UreI is an inner membrane protein with six transmembrane segments as shown by in vitro transcription/translation and membrane separation. Expression of UreI in Xenopus oocytes results in acid-stimulated urea uptake, with a pH profile similar to activation of cytoplasmic urease. Mutation of periplasmic histidine 123 abolishes stimulation. UreI-mediated transport is urea specific, passive, nonsaturable, nonelectrogenic, and temperature independent. UreI functions as a H+-gated urea channel regulating cytoplasmic urease that is essential for gastric survival and colonization.

Antral-type mucosa in the gastric incisura, body, and fundus (antralization): a link between Helicobacter pylori infection and intestinal metaplasia?

OBJECTIVES

Helicobacter pylori is a carcinogen; gastric carcinoma involves a multistep process from chronic gastritis to atrophy, intestinal metaplasia, and dysplasia. The aims of this study were to determine the types of mucosa at different gastric sites in H. pylori-infected and uninfected patients, and whether the presence of antral-type mucosa in the incisura, body, and fundus is associated with gastric atrophy and intestinal metaplasia.

METHODS

Two hundred and sixty-eight patients with dyspepsia were enrolled. Eight biopsies (i.e., antrum x3, body x2, fundus x2, and incisura x1) were obtained. One antral biopsy was used for the CLO-test. Three (each from the antrum, body, and fundus) were cultured. The remaining biopsies were examined histologically according to the updated Sydney System after staining with hematoxylin and eosin and Giemsa. A validated serological test was also applied.

RESULTS

Overall, 113 (42%) patients were infected with H. pylori. At the incisura, antral-type mucosa was more prevalent in infected than in uninfected patients (84% vs. 18%; odds ratio [OR] = 23.9, 95% confidence interval [CI] 12.5-45.8; p<0.001). Atrophic gastritis and intestinal metaplasia at the incisura was present in 19.5% and 13.3%, respectively, of infected, and 4.5% and 3.2%, respectively, of uninfected patients (both p<0.01). Moreover, atrophic gastritis at the incisura was associated with the presence of antral-type mucosa at the site (termed antralization); the prevalence of atrophic gastritis was 19.5% (24/123) in the presence of antralization, whereas the rate was 2.1% (3/145) without antralization (OR = 11.4, 95% CI 3.4-39.2; p<0.001). Similarly, at the incisura, 16.3% (20/123) of "antralized" cases and 1.4% (2/145) of "unantralized" cases had intestinal metaplasia (OR = 13.8, 95% CI, 3.2-60.7; p<0.001). The association between antralization at gastric body and fundus also appeared to be associated with atrophic gastritis and intestinal metaplasia at these sites.

CONCLUSIONS

Atrophic gastritis and intestinal metaplasia occurs predominantly at the gastric antrum and incisura with H. pylori infection. Antralization of the gastric incisura is a common event in H. pylori-infected patients, and appears to be associated with an increased risk of atrophic gastritis and intestinal metaplasia.

Helicobacter pylori and gastroesophageal reflux disease

The nature of the relationship between Helicobacter pylori (Hp) infection and gastroesophageal reflux disease (GERD) remains unclear. This article reviews the current body of knowledge regarding the association between these two common entities. The authors examine the potential interactions of Hp and GERD from epidemiologic and pathophysiologic viewpoints and summarize and critique the prevalence and eradication studies that have been performed to date. Special consideration is given to the possible effects that long-term use of proton pump inhibitors may have on Hp gastritis.

Impact of Helicobacter pylori infection on serum gastrin in haemodialysis patients

BACKGROUND

Helicobacter pylori infection is associated with increased gastrin release in patients with normal renal function. Hypergastrinaemia is a common finding in haemodialysis patients and, in many cases, may be linked to H. pylori infection. The aim of this study was to examine the effect of H. pylori infection, and its eradication, on elevated gastrin levels in haemodialysis patients.

METHODS

Eighty-nine dyspeptic patients were included in the study. While 44 patients had normal renal function, the remaining 45 were end-stage renal failure patients. Patients were assigned to one of four groups according to their H. pylori and renal function status. Infected patients were re-evaluated after 2 months following eradication treatment. Serum gastrin levels were measured in these groups both before and after eradication treatment.

RESULTS

Haemodialysis patients with H. pylori infection had higher serum gastrin levels than did H. pylori negative haemodialysis patients (321+/-131 pg/ml vs 154+/-25 pg/ml) (P<0.05). Mean serum gastrin concentration was 152+/-21 pg/ml in the non-uraemic H. pylori-positive group. This value was 58+/-17 pg/ml in the non-uraemic H. pylori-negative group (P<0.05). There were significant decreases in serum gastrin levels from pre- to post-eradication of H. pylori in the infected haemodialysis and non-uraemic patient groups (312+/-131 pg/ml to 179+/-85 pg/ml and 152+/-21 pg/ml to 72+/-2.4 pg/ml respectively, P<0.05). Four patients in group Ib and 5 patients in group IIb who had persistent infection did not have a decrease in serum gastrin level. All patients with successful eradication had a decrease in serum gastrin concentration.

CONCLUSION

Our findings suggest that H. pylori infection contributes to hypergastrinaemia in haemodialysis patients. More research is needed regarding the clinical consequences of hypergastrinaemia in these individuals.

Infection, immunity, and cancer

A significant percentage of human cancers worldwide are associated with infections due to known viruses, including human papillomaviruses (cervical cancer and other skin cancers), human T-lymphotropic viruses (adult T-cell leukemias and lymphomas in endemic areas), hepatitis B virus (liver cancer), and Epstein-Barr virus (Burkitt lymphoma and nasopharyngeal carcinoma). The fraction of human cancers attributable to infection may now need to be revised in light of the fact that new viral associations have been discovered and other nonviral associations have been identified. This article addresses the increasingly recognized role of infectious agents as precipitants of human neoplasia and the possibility that novel diagnostic, therapeutic, and chemopreventive strategies may emanate directly from research directed at identifying and understanding these agents.

The effect of dosing with omeprazole on the accuracy of the 13C-urea breath test in Helicobacter pylori-infected subjects

BACKGROUND

The 13C-urea breath test (13C-UBT) is an accurate means of Helicobacter pylori diagnosis. However, proton pump inhibitors may suppress H. pylori and cause false negative results.

AIM

To study the kinetics of H. pylori suppression by omeprazole during and after short-term use.

METHODS

Volunteers underwent a baseline 13C-UBT (13C-urea 100 mg). H. pylori-positive subjects took omeprazole 20 mg daily for 14 days. Those who remained 13C-UBT positive (delta13CO2 >/= 5) continued omeprazole for a further 14 days. 13C-UBTs were performed weekly on omeprazole and then every second day after it was stopped. False negatives occurred when delta13CO2 fell to < 5.

RESULTS

In 25 H. pylori-positive subjects (mean age 43.9 +/- 2.4 years; 21 females, 4 males) the mean baseline delta13CO2 was 28.1 +/- 3.4. False negative breath tests occurred in three subjects after 7 days of omeprazole and in a further four subjects after 14 days. A further six subjects developed negative tests between Days 14 and 28. Following cessation of omeprazole, the 13C-UBT became positive again in 12/13 subjects within 4 days and in all within 6 days, with a mean recovery to 99.9 +/- 18.6% of baseline delta13CO2.

CONCLUSIONS

False negative 13C-UBTs are common during treatment with omeprazole and occur after as little as 7 days. Return to positive test results is rapid after cessation of omeprazole. These findings are relevant to the timing of testing in clinical practice.

Host determinants of Helicobacter pylori infection and its clinical outcome

Greater than one-half of the world's population harbors Helicobacter pylori. The majority of infected individuals, however, remain asymptomatic, with only 10% to 20% developing diseases, including peptic ulcer disease, gastric cancer, and gastric mucosa-associated lymphoid tissue lymphoma. This article reviews host factors that may predispose an individual to both the acquisition of H. pylori infection and subsequent clinical outcome. Individuals with specific blood group antigens and human leukocyte antigen genotypes may be more susceptible to H. pylori infection. Additional factors, such as the age of acquisition, the host immune response, the site of infection, acid secretion, and interactions with nonhost factors (including bacterial virulence factors and environmental influences) may play a role in determining clinical outcome. Further investigation is required to clarify the mechanisms by which these interactions occur and, more critically, to determine their relative importance. This knowledge will enable the identification of individuals at risk of developing clinical disease with H. pylori infection.

Metabolism and genetics of Helicobacter pylori: the genome era

The publication of the complete sequence of Helicobacter pylori 26695 in 1997 and more recently that of strain J99 has provided new insight into the biology of this organism. In this review, we attempt to analyze and interpret the information provided by sequence annotations and to compare these data with those provided by experimental analyses. After a brief description of the general features of the genomes of the two sequenced strains, the principal metabolic pathways are analyzed. In particular, the enzymes encoded by H. pylori involved in fermentative and oxidative metabolism, lipopolysaccharide biosynthesis, nucleotide biosynthesis, aerobic and anaerobic respiration, and iron and nitrogen assimilation are described, and the areas of controversy between the experimental data and those provided by the sequence annotation are discussed. The role of urease, particularly in pH homeostasis, and other specialized mechanisms developed by the bacterium to maintain its internal pH are also considered. The replicational, transcriptional, and translational apparatuses are reviewed, as is the regulatory network. The numerous findings on the metabolism of the bacteria and the paucity of gene expression regulation systems are indicative of the high level of adaptation to the human gastric environment. Arguments in favor of the diversity of H. pylori and molecular data reflecting possible mechanisms involved in this diversity are presented. Finally, we compare the numerous experimental data on the colonization factors and those provided from the genome sequence annotation, in particular for genes involved in motility and adherence of the bacterium to the gastric tissue.

Imidazoline recognition sites and stomach function

Radioligand binding experiments carried out in cell membranes from rat and human stomach revealed the existence of non-adrenoceptor [3H]clonidine and [3H]idazoxan binding sites and of [3H]DTG (1,2-di-(2-tolyl)guanidine) binding sites. In rat stomach, specific binding was inhibited by imidazolines and guanidines and by non-imidazoline sigma-site ligands, respectively, at different rank orders of affinity, suggesting the existence of non-I1/non-I2 [3H]clonidine binding sites, I2-imidazoline binding sites as well as sigma 2-like-sites. These sites are not directly related to a postsynaptic contractile effect on rat gastric smooth muscle or to acid release from isolated gastric glands. Finally, we demonstrated that the gastric pathogen Helicobacter pylori is able to form and to release the endogenous imidazoline receptor ligand agmatine and that considerable amounts of agmatine are present in human gastric juice. The quantities of agmatine were higher in gastric juice from H. pylori-positive than H. pylori-negative patients.

The gastric transitional zones: neglected links between gastroduodenal pathology and helicobacter ecology

The gastric transitional zones are the junctional zones between the different types of mucosa: antral-body, body-cardia, and antrum-duodenum. In this article, the importance of the transitional zone in determining disease outcome, specifically duodenal ulcer, gastric ulcer, and possibly gastric cancer, is reviewed. Both gastric ulcers and duodenal ulcers are located immediately adjacent to the transitional zones. The transitional zones are dynamic rather than static areas. Local acid levels determine the behavior of Helicobacter pylori at the antral-body transitional zone and, as a consequence, the geographic distribution of gastritis in the stomach and the formation of duodenal ulcer and gastric ulcer. This review also explains that diffuse antral gastritis and multifocal atrophic gastritis are part of the same disease and not separate entities.

Helicobacter felis infection in dogs: effect on gastric structure and function

The relationship of Helicobacter felis, an organism that is observed in the stomachs of dogs, to gastric disease in dogs is unclear. The objective of this study was to determine if Helicobacter felis infection alters gastric morphology and gastric secretory function in dogs. Five specific-pathogen-free (SPF), Helicobacter-free Beagle dogs were examined before and for 26 weeks after inoculation with H. felis (ATCC 49179). Three SPF uninfected dogs served as controls. All five dogs became colonized by H. felis as determined by urease activity, histopathology, polymerase chain reaction, and transmission electron microscopic examination of serial gastric biopsies. The degree of colonization ranged from < 1 organism/400 x field to > 10 organisms/400 x field. The fundus, body, and cardia were most heavily colonized. Evaluation of gastric biopsies showed mild gastric inflammation and lymphoid follicles in both infected and uninfected dogs. There was no correlation between the number of organisms observed and the degree of gastric inflammation or number of lymphoid follicles. The gastric secretory axis, assessed by fasting and meal-stimulated plasma gastrin, mucosal gastrin and somatostatin immunoreactivity, fasting gastric pH, and pentagastrin-stimulated gastric acid secretion, was similar in both infected and uninfected dogs. Fasting gastric pH was not a reliable indicator of gastric secretory function. These findings suggest that H. felis may not be a gastric pathogen in dogs. However, the density of colonization and limited duration of infection should be considered when interpreting these findings.

Helicobacter pylori and the efficacy of omeprazole therapy for gastroesophageal reflux disease

OBJECTIVE

Helicobacter pylori infection may affect gastric acid output and intragastric pH. In patients with an insufficient lower esophageal sphincter, this effect may theoretically influence the severity of reflux disease, as well as the efficacy of acid suppressive therapy. To evaluate whether the H. pylori status of patients with gastroesophageal reflux disease (GERD) affects the severity of disease and the efficacy of omeprazole therapy to maintain disease remission, we conducted this study.

METHODS

Patients with GERD were prospectively studied by upper gastrointestinal endoscopy with biopsy sampling for histology and H. pylori culture before start of treatment and at annual follow-up. At endoscopy, esophagitis was graded according to the criteria of Savary-Miller, and the presence of Barrett's esophagus, hiatal herniation, or other abnormalities was recorded. Omeprazole was started at an initial dose of 20 mg daily; the dose was adjusted based on symptoms and the endoscopical findings.

RESULTS

One hundred thirty-seven GERD patients were included and followed up for a mean 56.6 months; 49 (36%) of them were infected with H. pylori. H. pylori-infected and -uninfected patients did not differ with respect to age (60 +/- 13 vs 61 +/- 14 yr, p = 0.65) or duration of follow-up (54 +/- 30 vs 58 +/- 31 months, p = 0.12). H. pylori-negative patients tended to present with more severe esophagitis at baseline (median Savary-Miller score 3 vs 2, p = 0.06) and had a higher prevalence of Barrett's esophagus (39/88 vs 10/49, p = 0.006). However, no difference was found with respect to the dose of omeprazole needed for maintained relief of symptoms and endoscopical signs of esophagitis (median 40 mg in both groups, p = 0.35).

CONCLUSIONS

H. pylori-negative GERD patients have a higher prevalence of Barrett's esophagus, but do not need a higher dose of omeprazole to maintain symptomatic and endoscopical disease remission.