Gastric Urease Activity Research Articles

Association of cagA+ Helicobacter pylori strains with high urease activity and dyspepsia in Mexican adults

Introduction and aimsHelicobacter pylori (H. pylori) is associated with a higher risk of peptic ulcer and gastric cancer. The sole presence of the bacterium is not a determinant of clinical outcome, but rather the interaction of strain type and host factors determines the risk of disease. Our aim was to study the association between bacterial load, strain type, and gastric symptoms in H. pylori-positive subjects. Materials and methodsIn a community survey, a diagnostic 13C-urea breath test for H. pylori was performed on 302 volunteers that were not taking antibiotics, antacids, or proton pump inhibitors one month prior to the test. The breath test produced 25 H. pylori-positive subjects, between 25 and 74 years of age, who then took a gastric symptoms survey and were tested for the presence of the cagA genotype in gastric juice, using the Entero-test®. Bacterial load was determined as a measure of urease activity, utilizing the delta over baseline (DOB) value, obtained in the 13C-urea breath test. ResultsA total of 48% of the H. pylori-positive subjects were cagA+. A positive association was found between cagA status and high gastric urease activity (p<0.0001) and the latter was significantly associated with the presence of symptoms (p<0.0001). ConclusionGastric urease activity was strongly associated with dyspeptic symptoms and cagA+H. pylori. Elevated 13C-DOB values could be used as indicators of a higher risk for gastric disease.

Protection Against Helicobacter pylori Infection in BALB/c Mouse Model by Oral Administration of Multivalent Epitope-Based Vaccine of Cholera Toxin B Subunit-HUUC.

Vaccination is an increasingly important alternative approach to control Helicobacter pylori infection, since H. pylori resistance to previously efficacious antibiotic regimens is increased, and H. pylori eradication treatment for upper gastrointestinal diseases is becoming less successful. Fortunately, an efficient oral monovalent H. pylori vaccine has been developed. However, compared with monovalent vaccines, multivalent vaccines have the potential to induce more effective and comprehensive protection against H. pylori infection. In this study, we designed and produced a multivalent epitope-based vaccine cholera toxin B subunit (CTB)-HUUC with the intramucosal adjuvant CTB and tandem copies of B-cell epitopes (HpaA132-141, UreA183-203, and UreB321-339) and T-cell epitopes (HpaA88-100, UreA27-53, UreB229-251, UreB317-329, UreB373-385, UreB438-452, UreB546-561, CagA149-164, and CagA196-217) from H. pylori adhesion A subunit (HpaA), urease A subunit (UreA), urease B subunit (UreB), and cytotoxin-associated antigen (CagA). Serum IgG, stomach, and intestine mucosal sIgA from mice after CTB-HUUC vaccination neutralized H. pylori urease activity in vitro. CTB-HUUC vaccination promoted H. pylori-specific lymphocyte responses and a mixed CD4+ T cell immune response as indicated by IFN-γ, interleukin-4, and interleukin-17 production in mice. Both oral prophylactic and therapeutic CTB-HUUC vaccinations reduced gastric urease activity and H. pylori infection and protected stomachs in mice. Taken together, CTB-HUUC is a promising potent and safe multivalent vaccine in controlling H. pylori infection in BALB/c mouse model.

Delta13CO2 excretion and expression of dyspeptic symptoms in patients evaluated for Helicobacter pylori infection by [13C] urea breath test.

Previous studies showed that either the urease activity possessed by H. pylori and the bacterial load may influence the results of the [13C] urea breath test. However, the correlation between urease activity and dyspepsia is unclear. The aim of our study was to evaluate whether the urease activity of the gastroduodenal tract may influence the severity of dyspeptic symptoms. In all, 2520 dyspeptic patients (1109 men, 1411 women; mean age 47 +/- 16 years) without gastroesophageal reflux disease, diabetes, vascular disorders, liver and biliary tract diseases, and tumors of the gastrointestinal tract and with a normal appearing abdominal ultrasonography were enrolled. All these patients underwent a [13C] urea breath test and filled out a questionnaire on dyspeptic symptoms. Subjects were divided in five different groups according to delta over baseline (DOB) values (group 1 < 3.5, group 2 = 3.5-6; group 3 = 6.1-11, group 4 = 11.1-23, group 5 > 23.1). The prevalence and intensity of dyspeptic symptoms were compared among groups. In all, 1688 patients (67%, 928 females and 760 males; mean age 48 +/- 15 years) were H. pylori-positive. The chi-squared test and analysis of variance showed increase of frequency and intensity of each dyspeptic symptom according to DOB values. In conclusion, Dyspepsia may parallel gastric urease activity. However, whether higher DOB values are related to higher bacterial load or, alternatively, to the presence of particular H. pylori strains able to produce larger amounts of urease is uncertain.

Investigation of the mechanism how citric acid enhances gastric urease activity in man: Effect on gastric emptying and the electrogastrogram

Investigation of the mechanism how citric acid enhances gastric urease activity in man: Effect on gastric emptying and the electrogastrogram

Isolation of recombinant protective Helicobacter pylori antigens.

A total of seven clones producing both new and previously described Helicobacter pylori proteins were isolated from a library of H. pylori genomic DNA. The screening approach by which these proteins were detected relied on the use of antisera raised in mice vaccinated with Helicobacter felis sonicate plus cholera toxin, a regimen which protects mice from H. pylori challenge. This strategy was designed to maximize the possibility of obtaining antigens which might be capable of conferring protection from H. pylori infection. Two of the clones were shown to encode the urease enzyme and the heat shock protein HspB, which have already been identified as protective antigens. The other five clones were sequenced, protein coding regions were deduced, and these sequences were amplified by PCR for incorporation into Escherichia coli expression vectors. The proteins produced from these expression systems were purified to allow testing for protective efficacy in an H. pylori mouse model. All five proteins were able to facilitate the clearance of a challenge with H. pylori, as judged by an assay of gastric urease activity and light microscopy on stomach sections. These results clearly indicate that the screening strategy has successfully identified candidate vaccine antigens.

Oral immunization with recombinant Helicobacter pylori urease confers long-lasting immunity against Helicobacter felis infection

Recombinant Helicobacter pylori urease (rUre) has been shown to confer protection against challenge with Helicobacter felis in mice. The purpose of the present study was to examine duration of the immune response and long-term protective efficacy of immunization with rUre. Swiss Webster mice were orally immunized four times at weekly intervals with 100 μg rUre plus 5 μg heat-labile enterotoxin of Escherichia coli (LT) adjuvant, or with LT only. At 4, 10, 20 or 40 weeks post immunization, 25 rUre-immunized mice and 25 control mice were challenged with H. felis and sacrificed at 2 or 10 weeks post-challenge. H. felis infection was assessed by gastric urease assay and by histology. Anti- H. pylori urease specific antibody levels were measured in serum and saliva both pre- and post-challenge. Over the 40 week time period, the infection rates in rUre-immunized mice were significantly lower than those in controls ( p<0.05) as assessed by gastric urease activity. Protection ranged from 79–100% at 2 weeks post-challenge and 63–78% at 10 weeks post-challenge. Gastric bacterial density in rUre-immunized mice was significantly lower than that of controls ( p<0.03) as determined by histologic assessment. Anti-urease antibody levels remained elevated in the serum and mucosal compartments at 39 weeks following immunization. This study shows that immunization with rUre plus LT results in long-lasting protective immunity against challenge with H. felis.

Factorial Trial of Three Interventions to Reduce the Progression of Precancerous Gastric Lesions in Shandong, China: Design Issues and Initial Data

In the fall of 1995, 3411 subjects in 13 rural villages in Linqu County, Shandong Province, China, began participating in a blinded, randomized 2 3 factorial trial to determine whether interventions can reduce the prevalence of dysplasia and other precancerous gastric lesions. One intervention is treatment for infection by Helicobacter pylori with amoxicillin and omeprazole. A second is dietary supplementation with capsules containing vitamin C, vitamin E, and selenium. A third is dietary supplementation with capsules containing steam-distilled garlic oil and Kyolic aged garlic extract. Investigators will evaluate histopathologic endpoints after gastroscopies with biopsies from seven standard sites in 1999. Initial data from pill counts and sampled blood levels of vitamin E, vitamin C, and S-allylcysteine indicate excellent compliance. Subjects have tolerated all interventions well, although 3.1% of those assigned to amoxicillin and omeprazole developed rashes, compared to 0.3% to those in the control group. Preliminary breath tests demonstrate substantial reductions in gastric urease activity, an indication of infection by Helicobacter pylori, among those assigned to amoxicillin and omeprazole.

Gastric urease activity is inversely associated with the success of treatment for Helicobacter pylori: effect of sofalcone.

Eradication therapy for Helicobacter pylori (H. pylori) has been established. However, the physiological factors influencing the success of treatment remain unclear. The aim of this study was to analyze these factors and to evaluate the efficacy of sofalcone on H. pylori eradication therapy. Forty-four H. pylori-infected and peptic ulcer patients were enrolled in this study. Twenty-seven patients were treated with lansoprazole (LPZ, 30 mg o.d. for 1-8 weeks) and amoxicillin (AMPC, 500 mg q.i.d, 1-2 weeks), followed by 8 weeks of treatment with famotidine (FAM, 20 mg o.d.). Moreover, sofalcone (SOF, 100 mg t.i.d) was administered to 17 patients throughout the therapeutic period. Endoscopic and serologic evaluations and the urea breath test (UBT) were performed before therapy. At the endoscopic examination, mucosal samples were biopsied and then tissue myeloperoxidase (MPO) content, an index of neutrophil infiltration was measured. Cure of H. pylori infection was determined 8 weeks after the cessation of LPZ. This eradication regimen afforded an overall cure rate of 63.0% (17/27) without SOF and 76.5% (13/17) with SOF. In the control group, treatment success was inversely associated with pre-UBT value (gastric urease activity), whereas this association was not observed in the SOF group. Furthermore, in the patients exhibiting a high preUBT value (>40%), a twofold higher eradication rate was obtained by the administration of SOF. In patients who were successfully eradicated, mucosal MPO level was slightly higher than those of unsuccessful cases, whereas there was no significant association with serum pepsinogen (PG I, PG II) concentration and its ratio (PG I/PG II). These results suggest that a low UBT value is a factor predicting treatment success. SOF administration may improve the eradication rate, especially in the high-UBT subgroup.

Gastritis in urease-immunized mice after Helicobacter felis challenge may be due to residual bacteria

BACKGROUND & AIMS: Oral immunization with recombinant Helicobacter pylori urease (rUre) coadministered with a mucosal adjuvant protects mice against challenge with Helicobacter felis. In this study, the duration of protection and gastritis after challenge were characterized at sequential time intervals up to 1 year.METHODS: Outbred Swiss- Webster mice were orally immunized with rUre plus adjuvant and examined for the presence of H. felis infection and leukocyte infiltration into the gastric mucosa.RESULTS: When defined by gastric urease activity, 70%-95% of rUre-immunized mice were protected for between 2 and 57 weeks. Challenge with H. felis increased the inflammatory response in the gastric mucosa of rUre-immunized mice, which also had elevated CD4+ and CD8+ T cells. The CD8+ cells represented a population of gastric intraepithelial cells, which expressed the mucosal alpha E-integrin. Epithelial changes consisting of parietal cell loss and hyperplasia of the epithelium occurred in approximately 20% of the mice. Antimicrobial triple therapy significantly decreased the degree of gastritis and epithelial alteration in the stomach.CONCLUSIONS: These results indicate that oral immunization of mice with rUre produces a long- lasting inhibition of H. felis infection but that residual bacteria may produce a persistent lymphocytic infiltration under these experimental conditions.(Gastroenterology 1997 Oct;113(4):1118-28)

13C-UREA BREATH TEST FOR HELICOBACTER PYLORI MOUSE MODEL

A non-invasive method to evaluate Helicobacter pylori (H. pylori) infection status in a mouse model would be of great value. A rapid and inexpensive breath testing protocol was developed, using a modified disposable 50 ml syringe as a breath collection chamber. The 13C-urea breath test was adapted to the Sydney Strain 1 H. pylori mouse model. Effects of oral intake on breath test results were evaluated in vitro and in vivo. Both diet and coprophagia were found to contribute significantly to the urease activity detected. We found the minimum time required to restrict feed and coprophagia was 13 hours. Optimal dose of 13C-urea was 50 micrograms, which we dissolved in 0.1 ml of water, and administered by oro-gastric gavage after a baseline breath sample was collected. The optimal time to collect the other breath sample was found to be 8 minutes. The modified disposable 50 ml syringe provided a simple, reliable and economical breath collection chamber. Mean breath test results for a group of H. pylori infected mice were higher than mean results for control mice. For use in individual mice we found the breath test to have a sensitivity of 89% and a specificity of 52%. An inverse relationship between breath test values in control mice and time interval between tests was shown which led to difficulties in our attempts to follow establishment of H. pylori infection with frequent testing. This is the first report of adaptation of the 13C-urea breath test to a mouse model of H. pylori infection. Both feed type and coprophagia are critical determinants of gastric urease activity in vivo and must be controlled for 13C urea breath testing in this mouse model to be valid.

Gastritis and Helicobacter pylori: forty years of antibiotic therapy.

Helicobacter pylori has now been propelled into the forefront of gastroenterology, particularly the treatment of gastroduodenal ulcer, whereas its role in gastritis is still widely ignored, although this disease sparked much of the original observations. Forty years ago, it was shown for the first time that antibiotics can eliminate gastric ammonia production in man which suggested that this was due to eradication of bacterial urease activity. It was also found that the gastric juice ammonia concentration correlates with hypo- or anacidity in uremics and with mucosal inflammation in subjects with gastritis. In patients with nonalcoholic and alcoholic gastritis, the histology as well as the symptoms of gastritis were strikingly improved by antibiotic treatment. Beneficial effects of eradication of gastric urease activity and the resulting decreased ammonia production were also shown in patients with hepatic encephalopathy. Broader studies and clinical applications of these earlier findings are now warranted.

Sucralfate suppresses Helicobacter pylori infection and reduces gastric acid secretion by 50% in patients with duodenal ulcer

BACKGROUND & AIMS: The mechanism(s) by which sucralfate heals duodenal ulcers remains unclear. The aim of this study was to determine the effect of sucralfate on Helicobacter pylori infection and on the accompanying hypersecretion of gastric acid the infection induces in patients with duodenal ulcer. METHODS: Basal and gastrin-releasing peptide (GRP) stimulated gastrin release and acid secretion. H. pylori density, gastric urease activity, and severity of gastritis were studied in patients with duodenal ulcer who were positive for H. pylori before, during, and after 4 weeks' treatment with sucralfate (2 g twice daily). RESULTS: The density of H. pylori decreased by 70% during sucralfate treatment and returned to the pretreatment level after discontinuation of therapy. This suppression of H. pylori infection was accompanied by an 80% decrease in gastric urease activity. GRP- stimulated plasma gastrin concentrations, GRP-stimulated acid output, and basal acid output all decreased by approximately 50% during sucralfate therapy and returned to pretreatment levels after treatment was discontinued. CONCLUSIONS: These findings indicate that sucralfate markedly suppresses H. pylori infection and the accompanying hypersecretion of acid the infection induces in patients with duodenal ulcer. These effects are likely to be important mechanisms by which the drug promotes duodenal ulcer healing. (Gastroenterology 1996 Mar;110(3):717-24)

Effect of Sucralfate onHelicobacter pyloriand Severity of Gastritis in Patients with Duodenal Ulcer

Duodenal ulcer relapse rates have been reported to be lower following healing with sucralfate. The question arises whether this is related to an effect on Helicobacter pylori. In order to investigate this possibility, 43 patients with active duodenal ulcer were entered into a study. Endoscopy was performed at entry, following 6 weeks' treatment with sucralfate 1 g q.i.d., and at 4 and 12 weeks of post-documented healing. Antral and gastric corpus biopsies were taken for assessment of H. pylori status (CLOtest), density of infection, and severity of gastritis. In addition, 14C urea breath tests (UBT) were performed. Sucralfate therapy induced a significant decrease in the density of H. pylori infection, with a trend to improvement of the gastritis in the antrum, but not in the corpus. However, all patients remained CLOtest positive, and the overall gastric urease activity was unchanged following therapy. These effects did not appear to influence either initial duodenal ulcer healing or subsequent relapse rates. Sucralfate has a suppressive effect on H. pylori infection in the gastric antrum but the clinical relevance of this is uncertain.

Helicobacter pylori in patients with systemic sclerosis: detection with the 13C-urea breath test and eradication.

In patients with systemic sclerosis peristaltic abnormalities may delay gastric emptying, giving rise to bacterial overgrowth, including possibly Helicobacter pylori (HP). Infection with Helicobacter is an important risk factor for esophageal and gastric diseases, including esophagitis, gastritis and gastric cancer. The purpose of this prospective study was to assess gastric HP infection in patients with systemic sclerosis. In 12 patients with systemic sclerosis the newly introduced breath test with 13C-labelled urea was used for indirect detection of gastric urease activity due to HP infection. Five out of 12 patients gave Helicobacter-positive results (42%); 7 patients were negative for Helicobacter colonization (58%). Thus, the risk for gastric diseases caused by HP infection is enhanced in patients with systemic sclerosis compared with white healthy, asymptomatic persons examined in other studies. Helicobacter-positive patients were treated with 2 x 20 mg omeprazole and 4 x 500 mg amoxicillin over 14 days. Afterwards the 13C-urea breath test was repeated and showed negative results for Helicobacter in all systemic sclerosis patients treated. Dual therapy with omeprazole and amoxicillin therapy effectively eradicated HP. The 13C-urea breath test did not cause any side-effects and is therefore considered to be a non-invasive, non-toxic and safe method for the diagnosis and therapeutic control of Helicobacter-status.

Biometric evaluation of gastric urease activity in man.

The 14C-urea breath test is claimed to be the best test for detection of Helicobacter pylori infection. We present a procedure for estimating its cutoff value on the basis of biometric evaluation only, without involving other diagnostic methods. Cumulative gastric urease activity (CA) was determined during the first 30 min after oral administration of 14C-urea (92.5 kBq) in 56 random volunteers and 49 consecutive patients with peptic ulcer disease. The distribution of CA in random volunteers was positively skewed. Logarithmic transformation yielded two separate populations, each normally distributed. Their normal probability density functions intercepted at log cutoff value. A bimodal distribution of log CA was confirmed in patients with peptic ulcer disease before and after treatment aimed at H. pylori eradication. Cutoff values were determined for both random volunteers and patients with peptic ulcer disease. By application of the present procedure for determination of cutoff value, the 14C-urea breath test distinguishes between individuals who have an increased gastric urease activity and individuals who do not, with the smallest possible arbitrariness.

Is there a place for antacids in the treatment of Helicobacter pylori infection?

Two pilot studies were performed to determine whether aluminium-containing antacids may have a place in the treatment of Helicobacter pylori infection. The urease activity of H. pylori is cytopathic to gastric epithelium, and inhibition of this enzyme may have therapeutic potential. In the first study 24 subjects, 12 of which were infected with H. pylori, were given 1 tablet of chewable aluminium hydroxide-containing antacids 10 min before a 14C-urea breath test. Gastric urease activity was suppressed by 33.3% (p = 0.02) in the H. pylori-positive subjects (none became negative) within 40 min after administration of the tablet. Gastric H. pylori infection can be effectively eradicated by triple regimens containing bismuth salts, tetracycline, and metronidazole. Owing to adverse effects of this treatment and concern for possible neurotoxicity of bismuth, a bismuth substitute is warranted. Hence, in the second study, 20 subjects infected with H. pylori were treated with 1 antacid tablet 4 times daily between meals, plus 500 mg oxytetracycline and 200 mg metronidazole 4 times daily with meals for 2 weeks. Individual H. pylori status was assessed by the 14C-urea breath test. Four weeks after cessation of treatment, H. pylori was eradicated in 45% (9 of 20) of the subjects (95% confidence interval, 23.1-68.5%). Thirty per cent (6 of 20) observed one or more adverse effect regarded as moderate or severe, of which loose stools and headache were the most common.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of Gastric Urease Activity by Antacids

Campylobacter pylori (CP) infection among healthy employees at the section of gastroenterology was studied by means of the carbon-14 urea breath test. Fourteen of 46 individuals (30.4%) were infected with Campylobacter pylori (CP+). Eleven CP+ individuals were treated with a low-dose regimen of antacids (four tablets a day) for 2 weeks. The 14C recovery dropped from 8.36 +/- 1.26% before treatment to 5.70 +/- 1.24% (p = 0.023) approximately 12 h after the last intake of antacids, a 31.8% reduction, indicating suppression but no eradication of the C. pylori infection. A new breath test 2 weeks after cessation of treatment indicated that the suppressive effect of antacid on C. pylori infection was short-lived.

Pharmacological studies on the mechanism of gastric ammonia production in relation to peptic ulcer remedies.

1. Relationship between urease activity in gastric mucosa and ammonia content of gastric juice was examined in 3 species of laboratory animals. The close relation was confirmed between them. 2. Urease inhibitory effects of some agents were compared in vivo and their influence on gastric ammonia production was examined in mice. Benzohydroxamic acid, a specific inhibitor of urease, distinctively reduced gastric ammonia production. 3. By intravenous injection of urea, ammonia content of gastric juice was markedly increased. 4. Repeated administrations of urea activated gastric urease activity and gastric ammonia production. 5. Repeated administrations of urea reduced the incidence of gastric errosion which was induced by reserpine in mice. 6. All these results may suggest the important role of gastric urease in defensive mechanism of gastric mucosa.

The Distribution and Functional Changes of Gastric Urease Activity

Summary Our observations suggest that urease activity is located in both the parietal and the mucoid cells of the cat and dog gastric mucosa. In the parietal cells urease was present in all the investigated animals. Activity was higher on the lesser curvature than the greater curvature. Stimulation of secretion by feeding and histamine increased urease activity in the parietal cell zone. The urease activity in the fundic surface epithelium was very low in a resting state, but increased considerably during secretory stimulation. About two-thirds of the animals investigated exhibited urease activity in the pyloric mucosa. The urease activities observed at pH 7.9 and 5.3 were similar in both the fundus and the pylorus. The present data support the view that urease is of cellular origin and that bacterial sources cannot account for its occurrence at subepithelial levels.