Mechanism of strong resistance of Helicobacter pylori respiration to nitric oxide

The aim of the present work is to elucidate the mechanism by which the respiration of Helicobacter pylori but not of Escherichia coli shows a strong resistance to nitric oxide (NO). Nitric oxide strongly but reversibly inhibited the oxygen consumption by sonicated membranes from H. pylori and Triton X-100-treated cells. Although the sensitivity of the H. pylori respiration to cyanide was low, it also increased after the treatment with Triton X-100. Kinetic analyses revealed that NO was rapidly degraded by E. coli and the Triton X-100-treated H. pylori, but not by the intact H. pylori. Thus, the low sensitivity to NO might reflect the low affinity of the cytochrome c oxidase for this radical within the membrane/lipid bilayers of H. pylori. Such properties of the oxidase in H. pylori membranes may, at least in part, underlie the mechanism by which this bacterium thrives in NO-enriched gastric juice.

[Association among anti-CagA antibody detection, antibiotic susceptibility, and peptic ulcer in patients with Helicobacter pylori infection]

INTRODUCTION

The aim of this study was to determine the relationship among antibodies against virulence factors (CagA and VacA), clinical status and primary resistance in dyspeptic patients with Helicobacter pylori infection.

METHODS

Ninety-eight adult patients with Helicobacter pylori infection who underwent gastric endoscopy for dyspepsia were studied. Specific serum IgG antibodies against CagA and VacA proteins were detected by Western-blot (Helicoblot 2.0). Minimum inhibitory concentrations of metronidazole, amoxicillin, tetracycline and clarithromycin were determined with the E-test.

RESULTS

Thirty-nine patients presented peptic ulcer disease and 59 had non-ulcer dyspepsia. CagA protein was detected in 63 patients, and VacA protein in 52 subjects, and both were significantly associated with peptic ulcers (p 5 0.034 and p 5 0.029, respectively). Susceptibility results showed 38.8% of strains resistant to metronidazole and 10.3% resistant to clarithromycin. No resistance to amoxicillin or tetracycline was found. Susceptibility to clarithromycin was more frequent in ulcer patients than in non-ulcer dyspepsia patients (p 5 0.046). CagA protein was more frequent in patients with clarithromycin-sensitive strains (p < 0.001).

CONCLUSION

Antibodies against CagA protein were associated with higher antibiotic susceptibility in patients with ulcers or non-ulcer dyspepsia. Thus, anti-CagA antibody detection could be a useful marker of favorable prognosis with antibiotic treatment.

Antibacterial effect of Kampo herbal formulation Hochu-ekki-to (Bu-Zhong-Yi-Qi-Tang) on Helicobacter pylori infection in mice

Because Helicobacter pylori (H. pylori) infection is a major cause of gastroduodenal diseases in humans, the eradication of H. pylori using antibiotics is very effective for the treatment of gastroduodenal diseases. However, it has recently been reported that resistance to these antibiotics is developing. In the present study, the antibacterial effect of a Kampo (traditional Japanese medicine) herbal formulation, Hochu-ekki-to (RET; Formula repletionis animalis et supletionis medii), against H. pylori was examined in vitro and in vivo. HET inhibited the growth of antibiotic-resistant strains of H. pylori as well as antibiotic-sensitive strains at a dose of 2.5 mg/ml in vitro. When 1,000 mg/kg of HET was administered orally to C57BL/6 mice for 7 days before or after inoculation with H. pylori, H. pylori in the stomach was significantly reduced in the HET-pre-treatment group compared with the control group. Furthermore, HET in combination with antibiotics completely eradicated the bacteria in mice. The expression of interferon (IFN)-gamma was induced in the gastric mucosa of the mice pre-treated with HET. There were no significant differences between the colonization of H. pylori in the control and HET treatment groups in IFN-gamma gene-deficient mice. These results suggest that the antibacterial effect of HET may be partly due to IFN-gamma induction, and that HET may be clinically useful for treatment of H. pylori infection.

A retrospective study on efficacy of proton-pump inhibitor-based triple therapy for eradication of Helicobacter pylori in patients with chronic renal failure

OBJECTIVE

The efficacy of short-course triple eradication therapy has been documented in patients with Helicobacter pylori infection and normal renal function. We have evaluated a one-week proton-pump inhibitor-based triple therapy for Helicobacter pylori eradication in a retrospective review of patients with chronic renal failure.

METHODS

We studied 25 patients (mean age 65.1 +/- 2.4 years) with creatinine clearance <30 ml/min/1.73 m2 or serum creatinine level >200 micromol/L (13 on dialysis), who had Helicobacter pylori infection, documented by histological examination or rapid urease test, together with either peptic ulcer disease or severe gastritis. The combination of Omeprazole 20 mg BID or Lansoprazole 30 mg BID, amoxicillin 1 gm BID and clarithromycin 500 mg BID was given for one week, in addition to therapy for peptic ulcers. All patients were re-endoscoped four weeks later.

RESULTS

All but one patient (96%) had successful eradication. On repeat endoscopy, all 13 patients with peptic ulcers had healed ulcers. For the 12 gastritis patients, three became normal and nine had persistent gastritis. For patients not on dialysis, the serum creatinine level and creatinine clearance remained stable at two weeks after treatment (303 +/- 37 vs. 330 +/- 36 micromol/l, p=ns; 23.6 +/- 3.4 vs. 26.0 +/- 3.9 ml/min/1.73 m2, p=ns, respectively).

CONCLUSION

The short course triple therapy was highly efficacious for Helicobacter pylori eradication in patients with chronic renal failure, with no adverse effect on renal function.

Monotherapy with mastic does not eradicate Helicobacter pylori infection from mice

OBJECTIVE

To determine the ability of mastic monotherapy to eradicate Helicobacter pylori infection from mice.

MATERIALS AND METHODS

The susceptibility of H. pylori SS1 to mastic was assessed by broth dilution determination of the MIC and MBC. Mice were inoculated intragastrically with either a suspension of H. pylori SS1 (n = 70) or brain-heart infusion broth alone (n = 10). Mice were given antimicrobial chemotherapy 4 weeks after infection and were administered the mouse equivalent of either 2 g of mastic twice daily for 7 days or a triple therapy regimen containing the mouse equivalent of 400 mg of metronidazole, 250 mg of clarithromycin and 20 mg of omeprazole twice daily for 7 days. Mice were killed either immediately or 1 month after the completion of treatment, and their stomachs cultured for H. pylori.

RESULTS

The mastic MIC and MBC of H. pylori SS1 were 7.80 and 31.25 mg/L, respectively. The triple therapy regimen eradicated infection from 19 of 20 SS1-infected mice. Mastic failed to eradicate infection from any of the 18 SS1-infected mice (P < 0.001) and there was no signifi- cant reduction in gastric bacterial load in mice treated with this regimen.

CONCLUSION

Despite reported beneficial effects in ulcer patients and the good in vitro activity of mastic against H. pylori, this compound is unable to eradicate H. pylori infection from mice.

Antimicrobial activity of esomeprazole versus omeprazole against Helicobacter pylori

OBJECTIVE

Esomeprazole is an enantiomorph of omeprazole, which inhibits gastric acid secretion more effectively than omeprazole. As proton pump inhibitors also exert an antibacterial activity, we aimed to compare esomeprazole and omeprazole for their antimicrobial activity against Helicobacter pylori in vitro.

METHODS

We studied 52 H. pylori isolates obtained from gastric biopsies and inoculated onto agar plates containing the acid-converted drugs at different concentrations. The minimal concentrations that inhibited the growth of 50% and 90% of isolates were defined as MIC(50) and MIC(90).

RESULTS

The MIC(50) and MIC(90) of esomeprazole were 16 and 32 mg/L; and those of omeprazole were 32 and 64 mg/L. Overall, 63.5% of isolates showed the same susceptibility to both drugs; 17 isolates were two- to 64-fold more susceptible to esomeprazole and two isolates were two-fold more susceptible to omeprazole.

CONCLUSIONS

The increased antimicrobial activity in vitro of esomeprazole against H. pylori could contribute to improving the outcome of the eradication treatment of such an infection.

[Correlation of rdxA gene mutation and metronidazole resistance of Helicobacter pylori]

OBJECTIVE

To demonstrate the correlation of rdxA gene mutation and metronidazole (MTZ) resistance of H.pylori isolates in the local area.

METHODS

Clinical strains of H.pylori were isolated from gastric biopsy of patients. Resistance to metronidazole of the isolates was determined by using diffusion test and two fold dilution test. Genome DNAs of the isolates were prepared for PCR to detect rdxA gene. The target amplification products were sequenced after T-A cloning. The sequences were compared with the reported sequences from Hp26695 and 134 other strains of H.pylori.

RESULTS

MTZ resistance rate was 76.1% in 21 clinical isolates. The target fragment 886 bp in length containing rdxA gene could be successfully amplified. In comparison with the reported corresponding sequence of H.pylori stain 26695, homologies of the nucleotide sequences from the amplification products were 90.1% approximate, equals 95.1%. Mutations caused by base insertion/deletion and substitution in the MTZ resistance isolates were found. Among these mutations, two types of insertion mutations have not been reported in literatures. No same mutations were present in the MTZ sensitive isolates.

CONCLUSION

The rdxA gene mutation may play an important role in MTZ resistance of H.pylori.

Detection of Helicobacter pylori in paraffin-embedded and in shock-frozen gastric biopsy samples by fluorescent in situ hybridization

We report on the successful application of fluorescent in situ hybridization for detection of Helicobacter pylori and determination of its clarithromycin susceptibility in formalin-fixed and paraffin-embedded gastric biopsy specimens that had been prepared for pathological examination. This method is useful when results from conventional culturing with antibiotic susceptibility testing are not available.

[The role of nuclear factor kappa B in secretion of interleukin-8 by gastric cancer cell line SGC 7901 induced by Helicobacter pyiori]

OBJECTIVE

To investigate the role of nuclear factor kappaB (NF-kappaB) in the gastric inflammation induced by Helicobacter pylori (H. pylori).

METHODS

SGC-7901 was transfected with IkappaB (NF-kappaB inhibitor gene) by electroporation, (beta)lacZ activity assay was used to examine transfected efficacy. Expression of IkappaB was assessed by Western-blot. Different concentration of live and heat-killed Hp (ATCC 43504) and supernatant of liquid culture were cocultured with SGC7901-IkappaB and its negative control SGC7901- neo. Activation of intracellular NF-kappaB was examined by electrophoretic mobility shift analyses (EMSA) and luciferase report gene assay at different time point. IL-8 levels were measured by ELISA at different time point.

RESULTS

IL-8 release was evident 4 hours after infection of SGC-7901-neo with H. pylori, and this effect was dose-time dependent. SGC-7901-IkappaB in which NF-kappaB has not been activated could not secret IL-8 after infection with H. pylori.

CONCLUSION

Secretion of IL-8 by gastric epithelial cell upon H pylori infection is dependent on activation of NF-kappaB.

Photoeradication of Helicobacter pylori using 5-aminolevulinic acid: preliminary human studies

BACKGROUND AND OBJECTIVES

Helicobacter pylori (HP) is an endemic pathogenic bacterium causing gastritis and gastroduodenal ulceration in humans and is linked to the development of gastric malignancies. These first human in vivo studies investigated the photoeradication of HP using laser and white light.

STUDY DESIGN/MATERIALS AND METHODS

In 13 HP-positive volunteers, a zone of gastric antrum was irradiated with laser (410 nm, 50 J/cm(2)) or endoscopic white light (10 J/cm(2)) 45 minutes after oral 5-aminolevulinic acid (5-ALA) 20 mg/kg. HP-eradication was assessed by biopsy urease test and HP-culture from irradiated and control zones 5 minutes, 4 and 48 hours post-irradiation.

RESULTS

A maximum eradication effect was achieved at 4 hours post-irradiation when 85% of biopsies in the monochromatic and 66% in the white light exposed zones, and 58 and 33% in the respective control zones were HP-negative.

CONCLUSIONS

HP numbers were greatly reduced following exposure to 5-ALA and either laser or white light in vivo. Photoeradication appears feasible, but further light dosimetry and the development of convenient application methods is required.

Healing of active, non-atrophic autoimmune gastritis by H. pylori eradication

BACKGROUND AND AIMS

The antigastric antibodies present in Helicobacter pylori infection act as a marker for an ongoing antigastric autoimmune process in the gastric mucosa, which can already be diagnosed in the non-atrophic stage. In a retrospective, uncontrolled study, therefore, we investigated the question as to whether this type of gastritis can be healed by the eradication of H. pylori.

PATIENTS AND METHODS

In 80 patients with an active, not yet atrophic autoimmune gastritis, we analysed a maximum of four investigations per patient over a period of up to 39.5 months. The following parameters were graded in the antral and corpus mucosa prior to and after H. pylori eradication treatment: grade and activity of the gastritis, H. pylori colonization, atrophy, parietal cell hypertrophy, and incidence of intestinal metaplasia. In addition, the typical parameters for this type of gastritis, such as grade of the periglandular lymphocytic infiltration, grade of glandular destruction and incidence of nodular ECL cell proliferates in the corpus mucosa were determined.

RESULTS

In 64 patients (80%), H. pylori eradication treatment was followed by healing of the active autoimmune corpus gastritis, that is, the activity of the gastritis disappeared, and lymphocytic infiltration of the glands, glandular destruction and parietal cell hypertrophy was found to be significantly reduced.

CONCLUSIONS

Our uncontrolled, retrospective study confirms the existence of an active, not yet atrophic autoimmune gastritis as a sequela of H. pylori infection.

Role of the thioredoxin system and the thiol-peroxidases Tpx and Bcp in mediating resistance to oxidative and nitrosative stress in Helicobacter pylori

Helicobacter pylori possesses two distinct thioredoxin proteins (Trx1 and Trx2) which may play important roles in the ability of this bacterium to survive oxidative stress. Trx1 has previously been shown to be an electron donor in vitro for alkyl-hydroperoxide reductase (AhpC), one of three members of the peroxiredoxin family of antioxidant peroxidases present in H. pylori. In this study, mutants in the trxA1 and trxA2 genes encoding Trx1 and Trx2, respectively, and in the tpx and bcp genes, which encode the remaining two members of the H. pylori peroxiredoxin family, were constructed in order to determine their roles in resistance to damage by reactive oxygen and nitrogen species. Mutation of trxA1 led to a pronounced increase in sensitivity to oxygen, hydrogen peroxide and the superoxide generator paraquat, as well as to the nitric oxide (NO) releasers sodium nitroprusside (SNP) and S-nitrosoglutathione (GSNO), consistent with an in vivo role for Trx1 as a reductant for AhpC. A trxA2 single mutant grew normally in an atmosphere of 2 % (v/v) O(2) but grew very poorly in 10 % (v/v) O(2). It showed slight increases in killing by hydrogen peroxide, paraquat, SNP and GSNO compared to the wild-type, but was significantly more sensitive to cumene hydroperoxide in disc-diffusion assays. A trxA1 trxA2 double mutant was very sensitive to all of the oxidative and nitrosative stresses applied. Comparison of the phenotypes of the tpx and bcp mutants showed that Tpx plays a significant role in peroxide and superoxide resistance in H. pylori, while the role of Bcp is minimal. No evidence was obtained for a role for either Tpx or Bcp in resistance to the toxic effects of NO. The results show that a functional thioredoxin system is necessary for both oxidative and nitrosative stress resistance in H. pylori but, surprisingly, is not essential for viability despite the absence of glutathione and a glutaredoxin system in this bacterium.

Real-time PCR assay for rapid and accurate detection of point mutations conferring resistance to clarithromycin in Helicobacter pylori

The main cause of failure of Helicobacter pylori eradication therapy is resistance to clarithromycin. The resistance is due to three point mutations in two positions on the 23S rRNA (A2142C, A2142G, and A2143G). Our aim was to develop a rapid and accurate method to detect these mutations directly on biopsy specimens. We developed a real-time PCR that included a simultaneous detection of the amplicons by hybridization of two probes labeled with LC-Red and fluorescein by using the fluorescence resonance energy transfer (FRET) technology and melting curve analysis with the LightCycler thermocycler. The assay was first applied successfully on reference strains, reference plasmids, and H. pylori-negative biopsies. Biopsies from 200 patients having failed a first eradication attempt and for whom the H. pylori strain was available were then tested with the new assay. A result was obtained in 199 cases; a single genotype was detected in 157 cases, two genotypes were detected in 41 cases, and three genotypes were detected in one case. There were, in total, seven discrepancies between the real-time PCR and the phenotypic method of determination of clarithromycin susceptibility, and in an additional four cases the two phenotypic methods were in disagreement. PCR-restriction fragment length polymorphism was applied to a sampling of biopsies, including all of the cases with multiple genotypes and all the cases with discrepant results. Finally, in four cases with discrepant results, the real-time PCR detected the resistant population at a concentration so low that it could not be detected by the phenotypic method, while in three cases other mutations could be involved. This assay had an accuracy at least as satisfactory as that of the phenotypic tests and could be performed within 2 h, allowing it to be used before the administration of therapy in the case of a first H. pylori eradication.

Antagonism of Helicobacter pylori by bacteriocins of lactic acid bacteria

Antimicrobial activity of seven bacteriocins produced by lactic acid bacteria against Helicobacter pylori strains (ATCC 43504, Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH [DSM] 4867, DSM 9691, and DSM 10242) was investigated in vitro using a broth microdilution assay. The bacteriocins chosen for the study were nisin A; lacticins A164, BH5, JW3, and NK24; pediocin PO2; and leucocin K. Antimicrobial activity of the bacteriocins varied among the H. pylori strains tested, of which strain ATCC 43504 was the most tolerant. Among the bacteriocins tested, lacticins A164 and BH5 produced by Lactococcus lactis subsp. lactis A164 and L. lactis BH5, respectively, showed the strongest antibacterial activity against H. pylori strains. MICs of the lacticins against H. pylori strains, when assessed by the critical dilution micromethod, ranged from 0.097 to 0.390 mg/liter (DSM strains) or from 12.5 to 25 mg/liter (ATCC 43504), supporting the strain-dependent sensitivity of the pathogen. Pediocin PO2 was less active than the lacticins against four strains of H. pylori, and leucocin K was the least active peptide, with no inhibition toward H. pylori ATCC 43504. Anti-Helicobacter activity of lacticin A164 was dependent on initial inoculum size as well as concentration of the bacteriocin added.

Clarithromycin resistance among Helicobacter pylori strains isolated from children: prevalence and study of mechanism of resistance by PCR-restriction fragment length polymorphism analysis

Clarithromycin and metronidazole resistance was 29.1 and 23.9%, respectively, in 96 Helicobacter pylori strains obtained from pediatric patients. No resistance to amoxicillin was observed. Resistance according to patients' ages to clarithromycin and metronidazole was 45.4 and 18.2% in 22 patients from 4 to 8 years old, 30.2 and 20.7% in 53 patients from 9 to 13 years old, and 9.5 and 38.1% in 21 patients from 14 to 18 years old, respectively. The A2143G mutation was the most prevalent (82.1%) among clarithromycin-resistant strains.

[Dynamics of clinical symptoms, indices of quality of life, and the state of motor function of the esophagus and rectum in patients with functional dyspepsia and irritable bowel syndrome after Helicobacter pylori eradication]

94 patients with irritable bowel syndrome and functional dyspepsia were included in the study. To confirm the diagnosis of H. pylori infection, all patients underwent fibroesophagogastroduodenoscopy with histological and urea tests before and 5 weeks after treatment. Standard eradication was performed. 25 patients underwent intraesophageal and anorectal manometry using the Polygraf device, Sweden. The dynamics of clinical symptoms, life quality (SF-36), manometry data and data of the histological examination of the stomach mucous coat was assessed. 63.5% of patients had clinical improvements following the eradication. The threshold of rectal sensitivity rose in 40% of patients. The esophageal motor function normalized in 48% of patients. An improvement of the morphological picture of chronic gastritis was recorded in 58.7% of patients.

In vitro evaluation of Bacopa monniera on anti-Helicobacter pylori activity and accumulation of prostaglandins

Bacopa monniera is an Indian tratidional medicine widely used to improve intellectual functions. Earlier, we had reported the prophylactic and curative effects of standardized extract of Bacopa monniera (BME) in various gastric ulcer models. The effect was due to augmentation of the defensive mucosal factors like increase in mucin secretion, life span of mucosal cells and gastric antioxidant effect rather than on the offensive acid-pepsin secretion. The present study includes evaluation of standardized BME (bacoside A content--35.5 +/- 0.9) on other contributing factors towards ulcerogenesis. BME in the dose of 1000 microg/ml showed anti-Helicobacter pylori activity in vitrol and in the dose of 10 microg/ml increased in vitro of prostanoids (PGE and PGI2) in human colonic mucosal incubates. It may be concluded that these factors may contribute to antiulcerogenic activity of BME.

[The antimicrobial susceptibility test of Helicobacter pylori]

Now that treatment of H. pylori associated disease is becoming common in Japan, drug resistant--H. pylori has emerged as a problem to be solved. There is no standard method of H. pylori drug susceptibility test in Japan yet. There are several methods available: Disk test, E-test, microplate method and agar plate dilution method. The E-test is being the standard method in European countries and USA. However the microplate method has been reported as a same accuracy as the agar dilution method, and thought as being a new standard method in Japan. In 2000, The Japanese Society of Chemotherapy proposed that drug susceptibility test be standardized and listed the break point of MIC of amoxicillin(AMPC) and clarithromycin(CAM).