A systematic review of Helicobacter pylori eradication therapy--the impact of antimicrobial resistance on eradication rates

Structural basis of 5-nitroimidazole antibiotic resistance: the crystal structure of NimA from Deinococcus radiodurans

5-Nitroimidazole-based antibiotics are compounds extensively used for treating infections in humans and animals caused by several important pathogens. They are administered as prodrugs, and their activation depends upon an anaerobic 1-electron reduction of the nitro group by a reduction pathway in the cells. Bacterial resistance toward these drugs is thought to be caused by decreased drug uptake and/or an altered reduction efficiency. One class of resistant strains, identified in Bacteroides, has been shown to carry Nim genes (NimA, -B, -C, -D, and -E), which encode for reductases that convert the nitro group on the antibiotic into a non-bactericidal amine. In this paper, we have described the crystal structure of NimA from Deinococcus radiodurans (drNimA) at 1.6 A resolution. We have shown that drNimA is a homodimer in which each monomer adopts a beta-barrel fold. We have identified the catalytically important His-71 along with the cofactor pyruvate and antibiotic binding sites, all of which are found at the monomer-monomer interface. We have reported three additional crystal structures of drNimA, one in which the antibiotic metronidazole is bound to the protein, one with pyruvate covalently bound to His-71, and one with lactate covalently bound to His-71. Based on these structures, a reaction mechanism has been proposed in which the 2-electron reduction of the antibiotic prevents accumulation of the toxic nitro radical. This mechanism suggests that Nim proteins form a new class of reductases, conferring resistance against 5-nitroimidazole-based antibiotics.

The importance of the level of metronidazole resistance for the success of Helicobacter pylori eradication

AIMS

To evaluate the role of antibiotic susceptibility for the treatment outcome of proton pump inhibitor-dependent and independent Helicobacter pylori eradication regimens.

METHODS

In a placebo-controlled clinical study of peptic ulcer patients with H. pylori infection, patients were randomized to receive lansoprazole, clarithromycin and tinidazole twice-daily, clarithromycin and tinidazole once-daily with lansoprazole or with placebo. Helicobacter pylori status was assessed by culture and antibiotic susceptibility by E-test minimal inhibitory concentration (MIC) in 205 clinical isolates.

RESULTS

Primary resistance to clarithromycin and metronidazole was 1 and 76%, respectively. In metronidazole susceptible strains eradication rates were similar at > 90% for all treatment groups (P = 0.49). With low-level metronidazole resistance (4 microg/mL < MIC < 256 microg/mL), eradication rates were similar at >75% (P = 0.80). The major difference was found at high-level metronidazole resistance (MIC >or= 256 microg/mL) with 95%, 58% and 21% eradication in the lansoprazole, clarithromycin and tinidazole twice-daily, lansoprazole, clarithromycin and tinidazole once-daily and placebo, clarithromycin and tinidazole once-daily groups, respectively (P < 0.001).

CONCLUSION

In the absence of antibiotic resistance, a once-daily therapy of only clarithromycin and tinidazole can achieve a high rate of H. pylori eradication. Such a combination could offer a simpler and cheaper treatment option for developing countries. The standard, twice-daily proton pump inhibitor-based triple therapy was shown to be efficient in H. pylori eradication even in the presence of high-level metronidazole resistance.

Effects of lactose as an inducer on expression of Helicobacter pylori rUreB and rHpaA, and Escherichia coli rLTKA63 and rLTB

AIM: To demonstrate the effect of lactose as an inducer on expression of the recombinant proteins encoded by Helicobacter pylori ureB and hpaA, and Escherichia coli LTB and LTKA63 genes and to determine the optimal expression parameters.

METHODS: By using SDS-PAGE and BIO-RAD gel image analysis system, the outputs of the target recombinant proteins expressed by pET32a-ureB-E.coliBL21, pET32a-hpaA-E.coliBL21, pET32a-LTKA63-E.coliBL21 and pET32a-LTB-E.coliBL21 were measured when using lactose as inducer at different dosages, original bacterial concentrations, various inducing temperatures and times. The results of the target protein expression induced by lactose were compared to those by isopropyl-β-D-thiogalactoside (IPTG). The proteins were expressed in E.coli.

RESULTS: Lactose showed higher efficiency of inducing the expression of rHpaA, rUreB, rLTB and rLTKA63 than IPTG. The expression outputs of the target recombinant proteins induced at 37 °C were remarkably higher than those at 28 °C. Other optimal expression parameters for the original bacterial concentrations, dosages of lactose and inducing time were 0.8, 50 g/L and 4 h for rHpaA; 0.8, 100 g/L and 4 h for rLTKA63; 1.2, 100 g/L and 5 h for both rUreB and rLTB, respectively.

CONCLUSION: Lactose, a sugar with non-toxicity and low cost, is able to induce the recombinant genes to express the target proteins with higher efficiency than IPTG. The results in this study establish a beneficial foundation for industrial production of H pylori genetic engineering vaccine.

Use of imidazole-based eradication regimens for Helicobacter pylori should be abandoned in North India regardless of in vitro antibiotic sensitivity

BACKGROUND AND AIM

The purpose of this study was to compare the efficacy of tinidazole- versus clarithromycin-based triple regimens for eradication of Helicobacter pylori in North Indian patients of peptic ulcer disease, and to correlate the outcome with in vitro antibiotic susceptibility.

METHODS

One hundred and forty-six H. pylori-infected patients with active ulcer were included in the prospective, randomized study. A total of 70 patients received lansoprazole 30 mg b.d., amoxycillin 1000 mg b.d. and tinidazole 500 mg b.d. (LAT), and 76 patients received lansoprazole 30 mg b.d., amoxycillin 1000 mg b.d. and clarithromycin 500 mg b.d. (LAC) for 14 days. The H. pylori status was assessed by urea breath test, rapid urease test, and histology and antibiotic sensitivity pattern by Epsilometer test.

RESULTS

In per-protocol analysis of 112 patients the H. pylori eradication rate was 42.3% (95% confidence interval (CI): 0.29-0.56) in LAT, and 64.8% (95%CI: 0.52-0.78) in LAC (95%CI of difference of proportions: 0.13-0.33, P = 0.01). Ulcer healed in 69.2% in the LAT group (95%CI: 0.57-0.82) and 81.7% in the LAC group (95%CI: 0.72-0.92; P = 0.02). Antibiotic susceptibility testing was done in 31 patients. Metronidazole resistance was present in 41.9% isolates but was unrelated to the outcome of the LAT regimen.

CONCLUSION

Imidazole-based eradication regimens should be abandoned in North India regardless of in vitro susceptibility results.

The prolongation of triple therapy for Helicobacter pylori does not allow reaching therapeutic outcome of sequential scheme: a prospective, randomised study

BACKGROUND AND AIM

One-week triple therapy for Helicobacter pylori revealed, during these last few years, a decrease in the eradication rate, so that the prolongation of its duration has been proposed. A sequential scheme recently showed very satisfactory results. We performed a prospective randomised study with the aim of either evaluating whether the triple therapy prolongation may improve its effectiveness and comparing its outcome with that of sequential regimen.

PATIENTS AND METHODS

Three hundred and forty-two H. pylori positive patients completed the study. They were randomised to receive one of the following treatments: (i) a 7-day triple therapy comprising of rabeprazole (20 mg, b.i.d.) plus clarithromycin (500 mg, b.i.d.) and amoxycillin (1 g, b.i.d.); (ii) a 10-day triple therapy comprising the same scheme; (iii) a 10-day sequential regimen comprising of rabeprazole (20 mg, b.i.d.) plus amoxycillin (1 g, b.i.d.) for 5 days followed by rabeprazole (20 mg, b.i.d.) plus clarithromycin (500 mg, b.i.d.) and tinidazole (500 mg, b.i.d.) for the next 5 days. Therapeutic results were expressed using both intention-to-treat and per protocol analyses with 95% confidence intervals. A model of multivariate logistic regression analysis was performed using therapeutic outcome as a dependent variable and including endoscopic finding, smoking habit, age and sex as candidates for the model.

RESULTS

Sequential regimen showed a significant gain in the eradication rate as compared to the 7-day (P < 0.0001) and the 10-day (P < 0.01) triple therapies, respectively. Overall eradication was lower in smokers than in non-smokers, but the difference remained significant only in the 7-day triple therapy (P < 0.01). Additionally, the overall eradication was higher in peptic ulcer than dyspepsia (P < 0.01), even if this difference was significant only for both triple therapies.

CONCLUSIONS

Seven-day triple therapy achieves disappointing eradication rates in dyspeptics and smokers. Prolonging triple therapy to 10 days does not significantly improve the eradication rate. The novel 10-day sequential regimen is more effective and equally tolerated than the 10-day triple therapy.

Primary Helicobacter pylori resistance to metronidazole and clarithromycin in the Finnish population

AIM

To systematically determine Helicobacter pylori primary antimicrobial resistance in Finland and the associated demographic and clinical features.

METHODS

A total of 342 adult patients referred for gastroscopy at 23 centres in different parts of Finland and positive for the rapid biopsy urease test were recruited. Clinical and demographic data were collected via a structured questionnaire. Patients with positive H. pylori culture and successful antibiotic sensitivity determination by the E-test method (n = 292) were included in the present analysis.

RESULTS

The study population consisted of 134 men and 158 women, mean age 56 years (95% CI, 55-58 years). Resistance to metronidazole was 38% (110 of 292) and to clarithromycin 2% (seven of 292). Resistance to metronidazole was higher in women than in men (48% vs. 25%, P < 0.001). Previous use of antibiotics for gynaecological infections predicted metronidazole resistance (P = 0.01), and previous use of antibiotics for respiratory (P = 0.02) and dental infections (P = 0.02) the clarithromycin resistance. We observed no major geographical variations in metronidazole resistance.

CONCLUSIONS

The primary metronidazole resistance of H. pylori was 38% and was common in women previously treated for gynaecological infections. Primary clarithromycin resistance was uncommon (2%) and may associate with previous dental and respiratory infections.

Application of Maastricht 2-2000 guidelines for the management of Helicobacter pylori among specialists and primary care physicians in israel: are we missing the malignant potential of Helicobacter pylori?

BACKGROUND

The Maastricht 2-2000 guidelines on the current management of Helicobacter pylori infection were recently adopted by the Israeli Gastroenterological Association.

GOAL

To determine the impact of these clinical guidelines on the current knowledge, attitudes, and management of H. pylori among primary care physicians, hospital internists, and gastroenterologists in Israel.

STUDY

Self-administered, voluntary, anonymous questionnaires were given personally to 229 physicians, 73 primary care physicians, 71 internists, and 85 gastroenterologists. The questions evaluated 4 main issues in the management of H. pylori: (1). the optimal diagnostic test, (2). indications for eradication, (3). combination and duration of triple therapy, and (4). the need for confirmation following eradication.

RESULTS

There were significant variations in the adherence of those recommendations among gastroenterologists, internists, and primary care physicians. Specifically, 94.1% of gastroenterologists and 88.9% of internists consider the urea breath test the test of choice for H. pylori diagnosis compared with 60.0% of the primary care physicians. Significant differences in the eradication indications for mucosa-associated lymphoid tissue (MALT) lymphoma, first-degree relatives of gastric cancer patients, atrophic gastritis, functional dyspepsia, and concomitant use of nonsteroidal antiinflammatory drugs were demonstrated among gastroenterologists and the other groups.

CONCLUSIONS

Primary care physicians may not be aware of important indications for diagnosis and eradication of H. pylori related to the risk of gastric malignancy or concomitant use of nonsteroidal antiinflammatory drugs. Public health agencies may need to increase penetration of the Maastricht 2000 recommendations to primary care physicians.

Pharmacoeconomics of gastrointestinal drug utilisation prior and post Helicobacter pylori eradication

BACKGROUND

Eradication of Helicobacter pylori prevents recurrence of peptic ulcer. In pharmacoeconomic analyses it is often presumed that after successful eradication no more gastrointestinal drugs are used. We investigated this presumed positive monetary effect using General Practitioners prescribing data, including information in diagnosis.

METHODS

From the RNG-database we identified patients with a H. pylori eradication in the years 1997-2000. H. pylori eradication was defined as a prescription of two antibiotics and one gastrointestinal drug on the same day. Patients were divided into a group with diagnosed ulcers and a group without diagnosed ulcers. Gastrointestinal drug costs were calculated for 4 months prior to eradication and 9-12 months post eradication. For comparison costs in all periods were expressed per patient per period. For statistical analysis the paired t-test was used.

RESULTS

One hundred and two patients were eligible for evaluation. Of these patients 35 had a diagnosed ulcer and 67 had not. Generally the number of patients on gastrointestinal drugs decreased (61% prior vs. 33% post), however, the drug costs did not change (Euro 33 prior vs. Euro 34 post). Costs for proton pump inhibitors increased post eradication (Euro 14 prior vs. Euro 28 post). The ulcer and nonulcer group showed similar results.

CONCLUSION

Helicobacter pylori eradication is thought to be cost effective, however, we did not find a decrease in costs for all gastrointestinal drugs. There may be a great pharmacoeconomical advantage when it is possible to predict which patients are more likely to 'fail' eradication therapy.

Fast and accurate quantitative detection of Helicobacter pylori and identification of clarithromycin resistance mutations in H. pylori isolates from gastric biopsy specimens by real-time PCR

Rapid identification of patients infected with clarithromycin-resistant Helicobacter pylori without the need for culture can help to avoid useless prescriptions of clarithromycin. We developed and tested a routine real-time quantitative PCR assay dedicated to that purpose. One hundred ninety-six consecutive gastric biopsy specimens were examined by culture, histology performed by a trained physician, and rapid PCR with the LightCycler apparatus. Infection was defined as (i) positivity of culture, (ii) positivity of histology, or (iii) positivity of PCR if confirmed by positivity of a concomitant indirect test (serology or urea breath test). Susceptibility to clarithromycin was tested by E-test and PCR. The prevalence of infection was 33.7% (66 of 196 samples). The sensitivities of culture, histology, and PCR were 90.9% (60 of 66 samples), 87.9% (58 of 66 samples), and 97.0% (64 of 66 samples), respectively. The specificity of PCR was 94.6% (123 of 130 samples). The linearity of the PCR results was achieved over a 6-log range of input DNA, and we were able to accurately quantify as few as 300 bacteria and to qualitatively detect as few as 30 bacteria per DNA sample. For clarithromycin susceptibility testing, there was 98.2% (55 of 56 samples) concordance between E-test and PCR. Forty-eight strains were clarithromycin susceptible, and 9 strains were clarithromycin resistant. The single discrepancy concerned a culture which was a mixture of mutant and wild type, with a susceptible-to-resistant ratio of 11.5: the resistant population was detected by E-test but not by PCR. Our PCR assay is accurate for fast detection of H. pylori as well as of clarithromycin resistance and is also able to objectively determine bacterial density.

Beta-lactamase inhibitor enhances Helicobacter pylori eradication rate

OBJECTIVES

One-week triple therapy, a combination of acid suppression with two antibiotics, is the gold standard for anti-Helicobacter pylori treatment. There is increasing evidence of H. pylori resistance to classical triple therapy. Recently, it was reported that the amoxicillin-clavulanate combination had a slightly higher activity than amoxicillin alone against H. pylori, and that beta-lactamase inhibitors had 'in-vitro' antibacterial activity against H. pylori.

SETTING

To evaluate the efficacy of 1 week triple therapy omeprazole, clarithromycin and amoxicillin plus clavulanate compared with omeprazole, clarithromycin and amoxicillin for H. pylori eradication. The study was open randomized.

SUBJECTS

Sixty dyspeptic patients (36 male, 24 female; mean age 53 +/- 9 years) with Helicobacter pylori infection never treated before, were enrolled and randomly assigned to two different 7-day triple therapies: (i) (n = 30) amoxicillin 875 mg plus clavulanic acid 125 mg b.i.d., clarithromycin 500 mg b.i.d., omeprazole 20 mg b.i.d. (ACCO); (ii) (n = 30) amoxicillin 1 g b.i.d., clarithromycin 500 mg b.i.d., omeprazole 20 mg b.i.d. (ACO). Bacterial eradication was assessed by 13C-urea breath test 4-6 weeks after therapy. Information on gastrointestinal symptoms and antibiotic-related side-effects were recorded using a questionnaire.

RESULTS

All patients completed the study. A significantly higher H. pylori eradication rate with ACCO compared with ACO: (26/30) 86.6 vs. (20/30) 66.6%, respectively (P < 0.05) were observed. No major side-effects were reported, whilst 8% patients complained of mild side-effects; no significant differences were noted between the two groups.

CONCLUSIONS

Our results suggest that amoxicillin and clavulanate in combination achieve a higher H. pylori eradication rate than amoxicillin alone, without any increase in side-effects. The combination of amoxicillin and clavulanate may represent an alternative therapeutic scheme for the treatment of H. pylori infection.

Role of antibiotic sensitivity testing before first-line Helicobacter pylori eradication treatments

BACKGROUND

The resistance of Helicobacter pylori to antibiotics has been advocated as a major cause of treatment failure, and antimicrobial sensitivity testing has been proposed to improve efficacy; however, its role before first-line therapy has not been investigated in detail.

AIM

To assess whether antimicrobial sensitivity testing improves the eradication rate of first-line anti-Helicobacter treatments and to compare the effectiveness of ranitidine bismuth citrate and omeprazole in the presence of H. pylori resistance to antibiotics.

METHODS

Two hundred and forty-two patients were assigned to either empirical or antimicrobial sensitivity testing-based treatment; within each group, subjects were further randomized to receive ranitidine bismuth citrate, 400 mg b.d., tinidazole, 500 mg b.d., and clarithromycin, 500 mg b.d., or omeprazole, 20 mg b.d., clarithromycin, 500 mg b.d., and amoxicillin, 1 g b.d., for 1 week, with substitution of the resistant antibiotic in the antimicrobial sensitivity testing-based treatment group.

RESULTS

Eradication rates were 67% [confidence interval (CI), 55-79%] in the empirical treatment group and 76% (CI, 65-87%) in the antimicrobial sensitivity testing-based group (P=N.S.). The overall success rate was 60% (CI, 51-69%) with omeprazole and 82% (CI, 73-91%) with ranitidine bismuth citrate (P<0.03); the latter overcame antibiotic resistance in 12 of 15 strains vs. zero of eight strains by omeprazole.

CONCLUSIONS

Antimicrobial sensitivity testing before first-line treatment does not improve the eradication rate, which is greater when ranitidine bismuth citrate is included in the treatment.

Second-line treatment for failure to eradicate Helicobacter pylori: a randomized trial comparing four treatment strategies

AIM

To compare the efficacy of different regimens in patients in whom previous Helicobacter pylori eradication therapy has failed.

METHODS

In this study named StratHegy patients (n=287) were randomized to receive one of three empirical triple therapy regimens or a strategy based on antibiotic susceptibility. The empirical regimens were omeprazole, 20 mg b.d., plus amoxicillin, 1000 mg b.d., and clarithromycin, 500 mg b.d., for 7 days (OAC7), clarithromycin, 500 mg b.d., for 14 days (OAC14) or metronidazole, 500 mg b.d., for 14 days (OAM14). In the susceptibility-based strategy, patients with clarithromycin-susceptible strains received OAC14, whilst the others received OAM14. The 13C-urea breath test was performed before randomization and 4-5 weeks after eradication therapy.

RESULTS

In the intention-to-treat analysis, the eradication rates for empirical therapies were as follows: OAC7, 47.4% (27/57); OAC14, 34.5% (20/58); OAM14, 63.2% (36/57); it was 74.3% (84/113) for the susceptibility-based treatment (P<0.01 when compared with OAC7 and OAC14). In patients receiving clarithromycin, the eradication rates were 80% for clarithromycin-susceptible strains and 16% for clarithromycin-resistant strains; in patients receiving OAM14, the eradication rates were 81% for metronidazole-susceptible strains and 59% for metronidazole-resistant strains.

CONCLUSIONS

Eradication rates of approximately 75% can be achieved with second-line triple therapy based on antibiotic susceptibility testing. If susceptibility testing is not available, OAM14 is an appropriate alternative.

A novel effect of bismuth ions: selective inhibition of the biological activity of glycine-extended gastrin

Although bismuth salts have been used for over two centuries for the treatment of various gastrointestinal disorders, the mechanism of their therapeutic action remains controversial. Because gastrins bind two trivalent ferric ions with high affinity, and because ferric ions are essential for the biological activity of glycine-extended gastrin 17, we have investigated the hypothesis that trivalent bismuth ions influence the biological activity of gastrins. Binding of bismuth ions to gastrins was measured by fluorescence quenching and NMR spectroscopy. The effects of bismuth ions on gastrin-stimulated biological activities were measured in inositol phosphate, cell proliferation, and cell migration assays. Fluorescence quenching experiments indicated that both glycine-extended and amidated gastrin 17 bound two bismuth ions. The NMR spectral changes observed on addition of bismuth ions revealed that Glu-7 acted as a ligand at the first bismuth ion binding site. In the presence of bismuth ions the ability of glycine-extended gastrin 17 to stimulate inositol phosphate production, cell proliferation, and cell migration was markedly reduced. In contrast, bismuth ions had little effect on the affinity of the CCK-2 receptor for amidated gastrin 17, or on the stimulation of inositol phosphate production by amidated gastrin 17. We conclude that bismuth ions may act, at least in part, by blocking the effects of glycine-extended gastrin 17 on cell proliferation and cell migration in the gastrointestinal tract. This is the first report of a specific inhibitory effect of bismuth ions on the action of a gastrointestinal hormone.

Levofloxacin-based triple therapy vs. quadruple therapy in second-line Helicobacter pylori treatment: a randomized trial

BACKGROUND

Levofloxacin has been shown to be effective in Helicobacter pylori eradication. Two 10-day levofloxacin-based triple therapies were compared with standard 7- and 14-day quadruple regimens in second-line treatment.

METHODS

Two hundred and eighty consecutive patients who failed to respond to standard triple therapy (clarithromycin, amoxicillin, rabeprazole) were randomly assigned to four groups: (1) levofloxacin 500 mg o.d., amoxicillin 1 g b.d., rabeprazole 20 mg b.d. for 10 days (LAR, n = 70); (2) levofloxacin 500 mg o.d., tinidazole 500 mg b.d., rabeprazole 20 mg b.d. for 10 days (LTR, n = 70); (3) tetracycline 500 mg q.d.s., metronidazole 500 mg t.d.s., bismuth salt 120 mg q.d.s., rabeprazole 20 mg b.d. for 7 days (7TMBR, n = 70); and (4) for 14 days (14TMBR, n = 70). Helicobacter pylori status and side-effects were assessed 6 weeks after treatment.

RESULTS

The eradication rate was 94% in the LAR group and 90% in the LTR group in both intention-to-treat and per protocol analyses. Helicobacter pylori eradication was achieved in 63 and 69% of the 7TMBR group and in 69 and 80% of the 14TMBR group in intention-to-treat and per protocol analysis, respectively. Side-effects were significantly lower in the LAR and LTR groups than in the 14TMBR group.

CONCLUSION

Ten-day levofloxacin-based therapies are better than standard quadruple regimens as second-line option for H. pylori eradication.

Treatment options for patients with Helicobacter pylori infection resistant to one or more eradication attempts

Proton pump inhibitor-based triple regimens fail to cure Helicobacter pylori infection in at least 10-23% of treated patients. Re-treatment strategies after initial failure remain poorly defined. Of the factors leading to eradication failure, patients' compliance, gender, primary resistance to clarithromycin and metronidazole, and intragastric bacterial load appear to be the most important in determining treatment outcome. Empirical re-treatment should depend mainly upon the antibiotics initially used, as re-administration of the same compound (namely, metronidazole and clarithromycin) is not recommended. Quadruple therapy is usually suggested in this situation, but there is some reluctance to use it in clinical practice on account of the high number of tablets to be taken and concern about side-effects. The use of ranitidine bismuth citrate instead of a proton pump inhibitor plus a bismuth compound in triple second-line regimens has recently proven to be highly effective. Finally, rifabutin-based triple therapies have been shown to be a promising rescue strategy in patients who have failed two or more eradication attempts.

Antibiotic resistance of Helicobacter pylori: a cross-sectional study in consecutive patients, and relation to ethnicity

OBJECTIVES

To assess primary antibiotic resistance in a given population and relate the results to ethnicity.

MATERIALS AND METHODS

Consecutive cultures were tested for antibiotic susceptibility with the Etest. Three populations were studied separately: ethnic Dutch people, patients of Turkish descent, and patients originating from Africa and the Middle East.

RESULTS

Over a period of 5.5 years, 976 (32%) biopsy specimens from 3010 patients were positive for Helicobacter pylori. Metronidazole and clarithromycin resistance were present in 25.8% and 4.8% of the strains, respectively. The number of metronidazole-resistant strains showed a gradual decrease, while clarithromycin resistance showed a slight increase during the study period. Antimicrobial resistance in patients of Turkish descent and in those originating from Africa or the Middle East was significantly higher than in ethnic Dutch people, 35% and 9.1% versus 21% and 2.9%, respectively (P = 0.003 and P = 0.002).

CONCLUSION

It is important to take ethnicity into account when studying antibiotic resistance. The numbers of metronidazole- and clarithromycin-resistant strains can vary considerably between people of different ethnic origin living in the same region.

Review article: the treatment of refractory Helicobacter pylori infection

The occurrence of refractory Helicobacter pylori infection is increasing. When the bacteria are not eradicated it means that the antibiotics have not reached the gastric mucosa at a sufficient concentration and over a sufficient time lapse to kill them. The main reasons for this are poor patient compliance, resistant bacteria, low gastric pH and a high bacterial load. Therefore, when administering a new treatment, it is important to choose antibiotics which do not face resistance problems and which increase the dosage of antisecretory drugs and the duration of treatment and, if possible, to add a topical agent such as bismuth salt. The recommended empirical strategy is to prescribe quadruple therapy or, alternatively, 2-week triple therapy including amoxicillin-metronidazole, tetracycline-metronidazole or amoxicillin-rifabutin. However, when H. pylori is susceptible, clarithromycin can still be used. In the case of a high level of metronidazole resistance, furazolidone can be employed. In each case, it is important to ensure good patient compliance, and counselling is helpful in this regard. However, the best approach remains the prevention of refractory H. pylori infection and, for this purpose, antimicrobial susceptibility testing before first-line therapy is important and should be encouraged.

Bismuth-based quadruple therapy using a single capsule of bismuth biskalcitrate, metronidazole, and tetracycline given with omeprazole versus omeprazole, amoxicillin, and clarithromycin for eradication of Helicobacter pylori in duodenal ulcer patients: a prospective, randomized, multicenter, North American trial

OBJECTIVES

This multicenter, randomized, active-controlled trial assessed efficacy of bismuth-based quadruple therapy with omeprazole, bismuth biskalcitrate, metronidazole, and tetracycline (OBMT) using a single-triple capsule of BMT compared with triple therapy with omeprazole, amoxicillin, and clarithromycin (OAC) in treatment of patients with Helicobacter pylori infection and duodenal ulcers.

METHODS

Patients with active duodenal ulcer or diagnosed within the past 5 yr and with infection documented by (13)C-urea breath test plus histology or culture were randomly assigned to 10-day course of OBMT using a single-triple capsule containing bismuth biskalcitrate 140 mg, metronidazole 125 mg, and tetracycline 125 mg given as three capsules q.i.d. with omeprazole 20 mg b.i.d., or a 10-day course of OAC, omeprazole 20 mg plus amoxicillin 1 g plus clarithromycin 500 mg, all b.i.d. Eradication was confirmed by two negative urea breath tests at >1 month and >2 months after therapy.

RESULTS

One hundred thirty-eight patients received OBMT and 137 OAC. Modified intent-to-treat eradication rates were 87.7% for OBMT and 83.2% for OAC (95% CI = -3.9%-12.8%; p = 0.29). OBMT eradicated 91.7% metronidazole-sensitive and 80.4% metronidazole-resistant strains (p = 0.06). OAC eradicated 92.1% clarithromycin sensitive and 21.4% clarithromycin-resistant strains (p < 0.001). Adverse events occurred in 58.5% of OBMT patients and 59.0% of OAC patients.

CONCLUSIONS

OBMT regimen using the single-triple capsule is as efficacious and well-tolerated as the widely used OAC regimen for H. pylori eradication. This OBMT therapy largely overcomes H. pylori metronidazole resistance, present in 40% of patients in this study.

The impact of Helicobacter pylori resistance on the efficacy of a short course pantoprazole based triple therapy

BACKGROUND: Many of the currently used Helicobacter pylori eradication regimens fail to cure the infection due to either antimicrobial resistance or poor patient compliance. Those patients will remain at risk of developing potentially severe complications of peptic ulcer disease. AIM: We studied the impact of the antimicrobial resistance on the efficacy of a short course pantoprazole based triple therapy in a single-center pilot study. METHODS: Forty previously untreated adult patients (age range 20 to 75 years, 14 males) infected with Helicobacter pylori and with inactive or healing duodenal ulcer disease were assigned in this open cohort study to 1 week twice daily treatment with pantoprazole 40 mg, plus clarithromycin 250 mg and metronidazole 400 mg. Helicobacter pylori was assessed at entry and 50 ± 3 days after the end of treatment by rapid urease test, culture and histology of gastric biopsies. The criteria for eradication was a negative result in the tests. Susceptibility of Helicobacter pylori to clarithromycin and metronidazole was determined before treatment with the disk diffusion test. RESULTS: One week treatment and follow up were complete in all patients. Eradication of Helicobacter pylori was achieved in 35/40 patients (87.5%) and was higher in patients with nitroimidazole-susceptible strains [susceptible: 20/20 (100%), resistant: 10/15 (67%)]. There were six (15%) mild adverse events reports. CONCLUSIONS: A short course of pantoprazole-based triple therapy is well tolerated and effective in eradicating Helicobacter pylori. The baseline metronidazole resistance may be a significant limiting factor in treatment success.

Indications for Helicobacter pylori eradication therapy and first-line therapy regimen in Japan: recommendation by the Japanese Society for Helicobacter Research

In November 2000, eradication therapy for Helicobacter pylori infection was approved under the present Japanese system of health insurance. Before the approval, the Japanese guideline of "Diagnosis and Treatment of H. pylori infection" was made by the guideline committee of the Japanese Society for Helicobacter Research. Indications for H. pylori eradication therapy were classified into three groups: (A) recommended: gastric and duodenal ulcers; (B) recommended and managed at a specialized institution: low-grade gastric mucosa-associated lymphoid tissue lymphoma; (C) current studies of the significance of the therapy: following endoscopic mucosal resection of early gastric cancer and gastric surgery for gastric cancers, hyperplastic gastric polyp, atrophic gastritis, and nonulcer dyspepsia. The first-line therapy regimen recommended is 1 week of triple therapy with a proton pump inhibitor standard dose twice a day, amoxicillin 750 mg bid, and clarithromycin 200 or 400 mg bid. The reasons for preferring this regimen are to avoid extensive use of metronidazole, which is allowed for treatment of Trichomonas infection in Japan, and the low rate of emergence of clarithromycin-resistant H. pylori with amoxicillin co-therapy. For second-line therapy patients should be referred to specialists, who can examine the susceptibility of H. pylori isolates against antibiotics and have much experience with this therapy.

Risk factors for failure of Helicobacter pylori therapy--results of an individual data analysis of 2751 patients

AIM

To study risk factors for failure of Helicobacter pylori eradication treatment.

METHODS

Individual data from 2751 patients included in 11 multicentre clinical trials carried out in France and using a triple therapy, were gathered in a unique database. The 27 treatment regimens were regrouped into four categories.

RESULTS

The global failure rate was 25.8% [95% CI: 24-27]. There was a difference in failure rate between duodenal ulcer patients and non-ulcer dyspeptic patients, 21.9% and 33.7%, respectively (P < 10(-6)). In a random-effect model, the risk factors identified for eradication failure in duodenal ulcer patients (n = 1400) were: to be a smoker, and to have received the group 4 treatment, while to receive a 10 day treatment vs. 7 days protected from failure. In non-ulcer dyspeptic patients (n = 913), the group 2 treatment was associated with failure. In both groups, age over 60 was associated with successful H. pylori eradication. There were less strains resistant to clarithromycin in duodenal ulcer patients than in non-ulcer dyspeptic patients. Clarithromycin resistance predicted failure almost perfectly.

CONCLUSION

Duodenal ulcer and non-ulcer dyspeptic patients should be managed differently in medical practice and considered independently in eradication trials.

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.

Impact of clarithromycin resistance and CYP2C19 genetic polymorphism on treatment efficacy of Helicobacter pylori infection with lansoprazole- or rabeprazole-based triple therapy in Japan

OBJECTIVE

Helicobacter pylori treatment failure is thought to be due mainly to polymorphic cytochrome P450 2C19 (CPY2C19) genetic polymorphism, associated with proton pump inhibitor metabolism, and antimicrobial susceptibility. This report has ascertained which was more important, CPY2C19 polymorphism or antimicrobial susceptibility, when using 1-week lansoprazole-based or rabeprazole-based triple therapy in Japan.

DESIGN

An open, randomized, parallel group study.

SETTING

One hundred and forty-five subjects with H. pylori-positive gastritis or peptic ulcers were randomly assigned to receive 30 mg lansoprazole twice daily (LAC group), 10 mg rabeprazole twice daily (RAC20 group), or 20 mg rabeprazole twice daily (RAC40 group), with 1000 mg amoxicillin twice daily and 400 mg clarithromycin twice daily for 1 week. Antimicrobial resistance testing was performed by E-test. More than 4 weeks after completion of treatment, H. pylori status was assessed by 13C-urea breath test, histology, and culture.

RESULTS

Cure rates expressed as intention-to-treat and per-protocol analyses, respectively, were 79.6 and 83.0% with LAC, 85.4 and 89.1% with RAC20, and 83.3 and 88.9% with RAC40. In the case of clarithromycin-sensitive strains, the cure rates were more than 97%, regardless of CPY2C19 polymorphism. However, treatment succeeded in only one out of 16 clarithromycin-resistant strains.

CONCLUSIONS

The key to successful eradication of H. pylori, using lansoprazole or rabeprazole with clarithromycin and amoxicillin, is clarithromycin susceptibility, not CPY2C19 polymorphism.

No association between Helicobacter pylori genotypes and antibiotic resistance phenotypes within families

BACKGROUND

Triple therapy combining a proton pump inhibitor with two antibiotics, e.g. clarythromycin (CLR), metronidazole (MTZ) or amoxicillin (AMX), represents the standard in Helicobacter pylori eradication regimens. Resistance to antimicrobial agents, particularly MTZ (up to 56% in Western countries) and CLR (up to 15% in southern Europe), is frequently observed and may be associated with treatment failure [1]. Recently, several studies indicated that individual H. pylori colonies from a single anatomic site may not always yield identical genotypes, or the identical patterns of susceptibility to antibiotics [2-5]. Representative for every single patient we analyzed 27 H. pylori antrum isolates for susceptibility to antimicrobial agents in order to test whether identical H. pylori genotypes exhibit a similar pattern of susceptibility to antibiotics.

METHODS

PCR, RELP, PFGE, antibiotic susceptibility testing.

RESULTS

H. pylori genotype and antibiotic susceptibility pattern in families do not segregrate.

CONCLUSION

Molecular typing of H. pylori from family members does not predict antibiotic susceptibility pattern.

A randomized comparison of quadruple and triple therapies for Helicobacter pylori eradication: The QUADRATE Study

BACKGROUND & AIMS

Direct comparisons of bismuth and proton pump inhibitor (PPI)-based triple and quadruple therapies for Helicobacter pylori eradication are lacking. To address this, a randomized study was conducted.

METHODS

Infected dyspeptic patients received pantoprazole 40 mg, amoxicillin 1000 mg, and clarithromycin 500 mg, all twice daily, for 7 days (PAC7); or pantoprazole 40 mg twice daily, bismuth subcitrate 108 mg, and tetracycline 500 mg, both 4 times daily, and metronidazole 200 mg 3 times daily and 400 mg at night for 7 days (PBTM7); bismuth subcitrate 108 mg and tetracycline 500 mg, both 4 times daily, and metronidazole 200 mg 3 times daily and 400 mg at night for 14 days (BTM14). Outcome was assessed with (13)C-urea breath test.

RESULTS

Eradication rates (intention to treat [n = 405]/per protocol [n = 320]) were similar for PAC7 (78%/82%) and PBTM7 (82%/88%); the latter significantly superior to BTM14 (69%/74%; P < 0.01). Pretreatment metronidazole resistance (MR) was 53% and clarithromycin resistance was 8%. Eradication rates for primary metronidazole sensitive/resistant isolates were 74%/87% with PAC7 and 80%/81% for PBTM7, compared with 76%/55% (P < 0.02) for BTM14. Noncompliance was greater with BTM14 (15%; P < 0.001) than PAC7 (3%) or PBTM7 (6%). Moderate-severe adverse events were more common with BTM14 (45%; P < 0.001), than PAC7 (23%) or PBTM7 (25%) with more discontinuations (9%, 2%, 3%, respectively).

CONCLUSIONS

One-week PPI triple therapy is well tolerated and effective. The addition of PPI to bismuth triple therapy allows reduction of treatment duration with improved efficacy and tolerability, despite a high rate of MR. Quadruple therapy appears to overcome pretreatment MR in most cases. Two-week bismuth triple therapy is significantly inferior to quadruple therapy and less well tolerated than both 1-week therapies.

One-week ranitidine bismuth citrate, amoxicillin and metronidazole triple therapy for the treatment of Helicobacter pylori infection in Chinese

BACKGROUND

We have previously shown that ranitidine bismuth citrate-based, clarithromycin-containing triple therapy achieves a higher eradication rate than proton pump inhibitor-based regimens in areas with a high prevalence of metronidazole resistance.

AIM

To evaluate whether this higher efficacy of ranitidine bismuth citrate over proton pump inhibitor can be extended to non-clarithromycin-containing regimens.

METHODS

Helicobacter pylori-positive dyspeptic patients were randomized to receive either ranitidine bismuth citrate, 400 mg, amoxicillin, 1000 mg, and metronidazole, 400 mg, or omeprazole, 20 mg, amoxicillin, 1000 mg, and metronidazole, 400 mg, each given twice daily for 1 week. H. pylori eradication was confirmed by 13C-urea breath test 5 weeks later. The side-effects of the treatments were documented.

RESULTS

Two hundred and twenty-nine patients were eligible for analysis. By intention-to-treat and per protocol analysis, the eradication rates were 77% and 79%, respectively, in the ranitidine bismuth citrate-amoxicillin-metronidazole group and 77% and 82%, respectively, in the omeprazole-amoxicillin-metronidazole group (P = 0.58 and P = 0.65). However, patients in the omeprazole-amoxicillin-metronidazole group reported a significantly higher incidence of minor side-effects when compared to those in the ranitidine bismuth citrate-amoxicillin-metronidazole group (P = 0.001).

CONCLUSIONS

Ranitidine bismuth citrate-amoxicillin-metronidazole was equally as effective as omeprazole-amoxicillin-metronidazole triple therapy, and may be considered as an alternative non-clarithromycin-based regimen in the Chinese population.

The effect of Helicobacter pylori retreatment with ranitidine bismuth citrate, clarithromycin, and metronidazole depends on the first-line therapy

BACKGROUND

Helicobacter pylori eradication rates seem to decrease. This study evaluates the effect of retreatment with ranitidine bismuth citrate (RBC) 400 mg B.I.D., clarithromycin (C) 500 mg B.I.D., and metronidazole (M) 500 mg every morning and 1,000 mg every evening for 14 days [RBC.C.M].

STUDY

Nine gastroenterologic units included patients with unsuccessful eradication of H. pylori in a preceding randomized trial. Previous treatment was either omeprazole (O) 20 mg, C 250 mg, and M 500 mg [O.C.M] or RBC 400 mg, tetracycline (T) 1,000 mg, and M 500 mg [RBC x T x M]; all drugs were given twice daily for 7 days.

RESULTS

Twenty-six H. pylori-positive patients were included (nine males, 17 females; mean age, 54 years; range, 39-74 years). The eradication rates in the groups previously treated with O.C.M and RBC.T.M were three of nine (33%) (95% CI = 12-65) and 15 of 17 (88%) (95% CI = 66-97) respectively (p = 0.008). The corresponding results in a "per-protocol" analysis were three of eight (38%) (95% CI = 13-69) and 10 of 10 (100%) (95% CI = 72-100), respectively (p = 0.007). A side effect score was 21.8 compared with 8.3 in the previous study (p < 0.001).

CONCLUSIONS

The effect of a retreatment regimen depends on the preceding treatment. The RBC x C x M regimen is effective in nonresponders to RBC x T x M, but it seems unsuitable after failure of the O x C x M regimen.

Impact of furazolidone-based quadruple therapy for eradication of Helicobacter pylori after previous treatment failures

BACKGROUND

One week of quadruple therapy including metronidazole is recommended for Helicobacter pylori treatment failures after first line therapy regardless of resistance status. This study investigated whether a quadruple regimen containing furazolidone could be effective as a third-line (salvage) therapy.

METHODS

All patients with previous H. pylori treatment failure after a clarithromycin-metronidazole +/- amoxicillin combination plus acid suppression were given lansoprazole 30 mg twice a day (bid), tripotassiumdicitratobismuthate 240 mg bid, tetracycline 1 g bid, metronidazole 400 mg (PPI-B-T-M) three times a day (tid) for 1 week. In the case of treatment failure with this second-line therapy, the same regimen was applied for 1 week except for using furazolidone 200 mg bid (PPI-B-T-F) instead of metronidazole (sequential study design).

RESULTS

Eighteen consecutive patients were treated with PPI-B-T-M. Eleven of those 18 remained H. pylori positive (38.9% cured). Pretherapeutic metronidazole resistance was associated with a lower probability of eradication success (10% vs. 75%, p=.04). Ten of these 11 patients agreed to be retreated by PPI-B-T-F. Final cure of H. pylori with PPI-B-T-F was achieved in 9/10 patients (90%) nonresponsive to PPI-B-T-M.

CONCLUSIONS

In the presence of metronidazole resistance, PPI-B-T-M as a recommended second-line therapy by the Maastricht consensus conference achieved unacceptable low cure rates in our metronidazole pretreated population. In this population, metronidazole based second-line quadruple therapy may be best suited in case of a metronidazole-free first line-regimen (e.g. PPI-clarithromycin-amoxicillin) or a low prevalence of metronidazole resistance. Furazolidone in the PPI-B-T-F combination does not have a cross-resistance potential to metronidazole and is a promising salvage option after a failed PPI-B-T-M regimen.

Effectiveness of Helicobacter pylori eradication treatments in a primary care setting in Italy

AIM

To evaluate the choice and relative effectiveness of Helicobacter pylori eradication regimens in a primary care setting.

PATIENTS AND METHODS

Patients referred to our department, who had been treated for H. pylori infection during the preceding 6 months, were enrolled between September 1998 and July 1999. H. pylori status was assessed by urea breath test. Information on the drugs administered, compliance and side-effects was recorded.

RESULTS

The mean eradication rate was 72% in patients receiving their first course of treatment (1863 cases; 45% male; mean age, 53 +/- 14 years); a double therapy regimen was prescribed to 14% of patients, triple therapy to 85% and quadruple therapy to 1%. Maastricht Consensus proton pump inhibitor-based regimens were prescribed in 80% of cases, with a mean eradication rate of 73%. No statistically significant correlation was found between eradication failure and sex, age, endoscopic findings or administered treatment.

CONCLUSIONS

In Italy, in a primary care setting, first-line H. pylori eradication therapies reflect international guidelines. The efficacy of such regimens is lower than that reported by controlled trials. These results are relevant when making pharmacoeconomic evaluations of H. pylori management.

Furazolidone-based triple 'rescue therapy' vs. quadruple 'rescue therapy' for the eradication of Helicobacter pylori resistant to metronidazole

BACKGROUND

The optimal treatment of patients with Helicobacter pylori resistant to metronidazole has not been established.

AIM

To compare the efficacy of quadruple and furazolidone-based triple therapy in the eradication of H. pylori resistant to metronidazole.

METHODS

Duodenal ulcer patients (n = 70) in whom initial eradication therapy failed and who harboured H. pylori strains resistant to metronidazole were randomized to receive one of the following 7-day regimens: colloidal bismuth subcitrate, 240 mg, tetracycline, 750 mg, and furazolidone, 200 mg, each given twice daily (BTF), or omeprazole, 20 mg b.d., colloidal bismuth subcitrate, 240 mg b.d., tetracycline, 500 mg q.d.s., and metronidazole, 500 mg b.d. (OBTM). H.pylori status was assessed by culture, histology and rapid urease test before treatment and 4-6 weeks after therapy. Susceptibility to metronidazole was assessed by the agar dilution method.

RESULTS

H. pylori eradication rates with intention-to-treat/per protocol analyses were: BTF, 85.7%/90.9%; OBTM, 74.2%/89.6%. Duodenal ulcers were healed in nine of 10 (90%) patients in the BTF group and in all patients (12/12) (100%) in the OBTM group (P = N.S.). A significantly lower rate of adverse events was observed in the BTF group than in the OBTM group (31.4% vs. 60%, P = 0.03), but there was no difference in terms of discontinuation of treatment (2/35 vs. 6/35, P = N.S.).

CONCLUSIONS

The 1-week BTF regimen was as effective as the OBTM regimen, and produced less adverse events. Thus, it may be used in patients in whom resistance of H. pylori to metronidazole is suspected.

Review article: Helicobacter pylori "rescue" regimen when proton pump inhibitor-based triple therapies fail

Even with the currently most effective treatment regimens, about 10-20% of patients will fail to obtain eradication of Helicobacter pylori infection. Therefore, in designing a treatment strategy, we should not focus on the results of primary therapy alone, but also on the final (overall) eradication rate. The choice of second-line treatment depends on which treatment was used initially, as re-treatment with the same regimen is not recommended. Therefore, it is not necessary to perform culture after the first eradication failure. Assessment of the sensitivity of H. pylori to antibiotics only after failure of the second treatment is suggested in clinical practice. Different possibilities of empirical treatment have been suggested. After failure of proton pump inhibitor-amoxicillin-clarithromycin, quadruple therapy has generally been used. More recently, replacement of the proton pump inhibitor and the bismuth compound by ranitidine bismuth citrate has also achieved good results. After proton pump inhibitor-amoxicillin-nitroimidazole failure, re-treatment with proton pump inhibitor-amoxicillin-clarithromycin has been proven to be effective. Finally, first-line treatment should not combine clarithromycin and metronidazole in the same regimen, because of the problem of resistance to both antibiotics. Recently, rifabutin-based rescue therapies have been shown to constitute an encouraging strategy for eradication failures, as they are effective against H. pylori strains resistant to antibiotics.

Potential of fumarate reductase as a novel therapeutic target in Helicobacter pylori infection

Approximately 50% of the world's population carries Helicobacter pylori, a gastric bacterial pathogen linked to diseases including gastritis, ulcers and gastric cancer. Chemotherapies are being routinely used to treat systemic H. pylori infection. The common regimens consist of proton pump inhibitors (PPIs) or ranitidine bismuth citrate (RBC) and two antibiotics. Although these regimens efficiently eradicate H. pylori, the emergence of antibiotic-resistant H. pylori strains, their severe side effects and high costs are major drawbacks of these treatments. More efficient, economic and friendly drugs need to be developed. Fumarate reductase (FRD) catalyses the reduction of fumarate to succinate in the Krebs cycle and is also a key enzyme in anaerobic respiration with fumarate as the terminal electron acceptor for many facultative bacteria. H. pylori FRD contains three subunits, FrdA, FrdB and FrdC. Genome analysis and experimental evidence indicate that this enzyme appears to play an important role in the energy metabolism of H. pylori. In addition, FRD is essential for the colonisation of H. pylori in the acidic stomach as demonstrated in the mouse model of infection. Furthermore, three FRD inhibitors used to cure helminthic infection in animals and humans have both inhibitory and bactericidal effects on H. pylori. These lines of evidence indicate that FRD may be a promising chemotherapeutic target. Given that FrdA is strongly immunogenic in the sera from H. pylori-positive patients, this protein may also be used as a candidate for the development of an anti-H. pylori vaccine.

Update on the management of Helicobacter pylori infection, including drug-resistant organisms

Helicobacter pylori infection has many different clinical outcomes. Not all infected persons need to be treated. Therefore, indications for treatment have to be clear, and several consensus guidelines have been formulated to aid the medical practitioner in this decision-making process. Triple therapy with a proton pump inhibitor (PPI), in combination with amoxicillin and clarithromycin is the established treatment of choice. For patients with penicillin hypersensitivity, metronidazole can be substituted for amoxicillin. Bacterial resistance to antibiotics is a major factor adversely affecting treatment success. Resistance to metronidazole has been reported in up to 80%, and resistance to clarithromycin in 2-10% of strains cultured. Resistance to either one of the antibiotics has been reported to result in a drop in efficacy of up to 50%. Emergence of resistance to both metronidazole and clarithromycin following failed therapy is a cause for concern; this underlines the need to use the best available first-line therapy. To avoid the emergence of resistance to both key antibiotics, the combination of metronidazole and clarithromycin should be avoided where possible. For failed treatment, several strategies can be employed. These include ensuring better compliance with repeat therapy, and maximizing the efficacy of repeat treatment by increasing dosage and duration of treatment, as well as altering the choice of drugs. Quadruple therapy incorporating a bismuth compound with a PPI, tetracycline and metronidazole has been a popular choice as a "rescue" therapy. Ranitidine bismuth citrate has been shown to be able to overcome metronidazole and clarithromycin resistance; it may be a useful compound drug to use in place of a PPI in "rescue" therapies. In the case of persistent treatment failures, it is useful to consider repeating gastroscopy and obtaining tissue for culture, and then prescribe antibiotics according to bacterial susceptibility patterns. It is also important in refractory cases to review the original indication for treatment and determine the importance of the indication.

Effectiveness of two quadruple, tetracycline- or clarithromycin-containing, second-line, Helicobacter pylori eradication therapies

BACKGROUND

There are no guidelines on second-line therapies for Helicobacter pylori eradication failures of omeprazole-clarithromycin-amoxicillin triple therapy.

AIM

To compare the efficacy of two second-line therapies for persistent H. pylori infection.

METHODS

Over a 6-year period, patients with persistent H. pylori infection following omeprazole-clarithromycin-amoxicillin eradication therapy were randomized to receive omeprazole, 20 mg twice daily, bismuth, 120 mg four times daily, metronidazole, 500 mg twice daily, and either tetracycline, 500 mg four times daily, or clarithromycin, 500 mg twice daily, given for 7 days. Before therapy, patients underwent endoscopy with biopsies for histology, culture and antibiotic susceptibility tests. H. pylori infection was confirmed by histology.

RESULTS

Of the 95 randomized patients, 88 (93%) completed the study. Age, sex, smoking, ulcer/non-ulcer dyspepsia ratio and antibiotic resistance were not significantly different between the treatment groups. On intention-to-treat analysis, eradication was achieved in 41 of the 49 patients (84%; 95% confidence interval, 70.4-92.7%) and 27 of the 46 patients (59%; 95% confidence interval, 43.3-73.0%) of the tetracycline- and clarithromycin-containing groups, respectively (P=0.007). On multivariate regression analysis, the sensitivity of H. pylori to metronidazole had a likelihood ratio of 5.2 (P=0.022), followed by the type of quadruple therapy (likelihood ratio, 4.4; P=0.036).

CONCLUSIONS

Tetracycline-containing quadruple rescue therapy is highly effective in treating H. pylori eradication failures of the omeprazole-amoxicillin-clarithromycin regimen.

Mono, dual and triple moxifloxacin-based therapies for Helicobacter pylori eradication

BACKGROUND

Moxifloxacin is a broad spectrum fluoroquinolone with single daily administration, currently used, above all, for respiratory tract infections.

AIM

To compare the efficacy of different 1-week moxifloxacin-based Helicobacter pylori eradication regimens.

METHODS

One hundred and twenty H. pylori-positive subjects were randomized to receive moxifloxacin (400 mg/day), moxifloxacin (400 mg/day) and lansoprazole (30 mg/day) or moxifloxacin (400 mg/day), lansoprazole (30 mg/day) and clarithromycin (500 mg b.d.). H. pylori status was reassessed 6 weeks after the end of therapy, and both intention-to-treat and per protocol analyses were performed.

RESULTS

One hundred and nineteen of the 120 patients completed the study. H. pylori eradication was achieved in 22.5% of patients treated with moxifloxacin, in 33.3% of subjects treated with moxifloxacin and lansoprazole and in 90% of patients treated with moxifloxacin, clarithromycin and lansoprazole.

CONCLUSIONS

Mono and dual moxifloxacin-based therapies are not acceptable for H. pylori eradication; conversely, moxifloxacin-based triple therapy may be considered as a new, effective, first-line therapy option.

Mechanism and clinical significance of metronidazole resistance in Helicobacter pylori

Metronidazole was introduced in 1959 for the treatment of Trichomonas vaginalis, but was subsequently shown to be active against anaerobic and some micro-aerophilic bacteria as well. In anaerobic microorganisms with their low redox potential, metronidazole is reduced to its active metabolite by a one-electron transfer step. Metronidazole is often used in treatment regimens for Helicobacter pylori, a microaerophilic bacterium, but resistance to this drug is frequently encountered. The metabolism of metronidazole in H. pylori must differ from that in anaerobic bacteria as metabolites formed by a one-electron transfer are readily re-oxidized in the micro-aerophilic environment of H. pylori. This process is called 'futile cycling' and is accompanied by the formation of toxic oxygen radicals that are neutralized by an active scavenger system. Recently, it has been shown that in H. pylori, in contrast to the situation in anaerobes, an oxygen-insensitive nitroreductase. encoded by the rdxA gene, is responsible for the activation of metronidazole. Activation by this enzyme is by a two-electron transfer step, preventing futile cycling' and thereby enabling the activation of metronidazole in a micro-aerophilic environment. Metronidazole resistance has been shown to be associated with null mutations in the rdxA gene in most clinical isolates. However, there may be some 'background metronidazole susceptibility' in metronidazole-resistant strains caused by other (oxygen-sensitive) nitroreductases. Recently, three meta-analyses of the impact of metronidazole resistance on treatment efficacy have all shown a significant reduction in efficacy of metronidazole containing regimens in patients infected with a resistant strain. The impact of resistance proved to be dependent on the other components of the regimen and on treatment duration.

High rate of post-therapeutic resistance after failure of macrolide-nitroimidazole triple therapy to cure Helicobacter pylori infection: impact of two second-line therapies in a randomized study

BACKGROUND

The optimal second-line treatment after failed Helicobacter pylori therapy has not been established.

AIMS

To ascertain whether quadruple therapy or triple therapy with omeprazole, clarithromycin and amoxicillin is the superior re-treatment after triple therapy containing a macrolide and a nitroimidazole, and to determine the impact of microbial in vitro resistance.

METHODS

Patients after failed triple therapy were randomly allocated to one of two 1-week second-line treatments: omeprazole, 40 mg, clarithromycin, 500 mg, and amoxicillin, 1 g, all b.d.; or omeprazole, 20 mg b.d., bismuth subsalicylate, 600 mg q.d.s., metronidazole, 400 mg t.d.s., and tetracycline, 500 mg q.d.s. Post-therapeutic Helicobacter pylori status was assessed by 13C-urea breath test at least 4 weeks after treatment.

RESULTS

The study was terminated after including 84 patients. H. pylori cure rates differed significantly: omeprazole-clarithromycin-amoxicillin: intention-to-treat, 43%; per protocol, 50%; omeprazole-bismuth subsalicylate-metronidazole-tetracycline: intention-to-treat, 68%; per protocol, 69%. The frequencies of resistance after first-line therapy were: metronidazole, 90%; clarithromycin, 71%; both combined, 68%. For clarithromycin resistance, H. pylori cure with omeprazole-clarithromycin-amoxicillin was 30% vs. 83% for clarithromycin susceptibility.

CONCLUSIONS

Omeprazole-bismuth subsalicylate-metron- idazole-tetracycline was superior to omeprazole-clarithromycin-amoxicillin, but both therapies yielded unsatisfactory results. The high rate of post-therapeutic dual resistance has a negative impact on omepraz- ole-clarithromycin-amoxicillin, and probably also on omeprazole-bismuth subsalicylate-metronidazole-tetracycline, and limits the choice for second-line treatment.

Primary resistance to antibiotics and its clinical impact on the efficacy of Helicobacter pylori lansoprazole-based triple therapies

AIM

To evaluate Helicobacter pylori primary resistance and its clinical impact on the efficacy of two lansoprazole-based eradication triple therapies.

METHODS

H. pylori-positive patients (n=228) were randomized to receive one of the 1-week regimens: lansoprazole 30 mg, clarithromycin 500 mg and amoxicillin 1 g (LAC), or lansoprazole 30 mg, clarithromycin 500 mg and metronidazole 500 mg (LMC), each given twice daily. H. pylori status was assessed by 13C-urea breath test and culture at diagnosis and by 13C-urea breath test 6 weeks after therapy. Antibiotic susceptibility was determined by E-test (n=98).

RESULTS

The eradication rates with per protocol/ intention-to-treat analyses were: LAC (n=95/114) 83%/69% and LMC (n=96/114) 85%/72%. Primary resistance was 11% for clarithromycin, 41% for metronidazole and 0% for amoxicillin. Eradication in metronidazole-susceptible/-resistant strains was 85%/82% in LAC and 83%/63% in LMC. Significantly lower cure rates were observed in clarithromycin-resistant patients treated with LAC (95% vs. 0%, P < 0.001) and LMC (86% vs. 0%, P < 0.001).

CONCLUSIONS

One-week LAC and LMC are similarly effective therapies. Clarithromycin resistance significantly affected H. pylori eradication in both regimens.

Metronidazole resistance in Helicobacter pylori

Modern triple drug regimens are highly effective for treating Helicobacter pylori infection, but bacterial resistance to one of the most effective antibiotics, metronidazole, is a serious and increasing problem. The activity of metronidazole in H. pylori is dependent on reduction of its nitro moiety to highly reactive compounds that cause DNA strand breakage. The acquisition of resistance is highly associated with mutational inactivation of the rdxA gene, which encodes an oxygen-insensitive NADPH nitroreductase. Recent evidence has suggested that inactivation of frxA (NADPH flavin oxidoreductase), fdxB (ferredoxin-like protein) and possibly other reductase-encoding genes may also contribute to the resistant phenotype. Improved understanding of the mechanisms of metronidazole resistance in H. pylori is essential for the development and validation of biopsy-based tests for detection of resistance in clinical practice.

Assessment of clarithromycin-resistant Helicobacter pylori among patients in Shanghai and Guangzhou, China, by primer-mismatch PCR

Of 96 Helicobacter pylori isolates from patients in Shanghai and Guangzhou, China, 5 had the A2143G 23S rRNA mutation as determined by primer-mismatch PCR and were resistant to clarithromycin by the E-test. The remaining isolates were primer-mismatch PCR negative and susceptible to clarithromycin. The conclusion is that the prevalence of clarithromycin-resistant H. pylori isolates among these Chinese patients is 5%.

Treatment of Helicobacter pylori infection. Indications and regimens: an update

The management of Helicobacter pylori infection is still surrounded by controversy and uncertainties. Indications and correct application of current regimens for Helicobacter pylori infection are still considered a matter of debate. Regarding indications, only peptic ulcer and mucosa associated lymphoid tissue lymphoma are considered clear indications for treatment. In other conditions, such as atrophic gastritis, post gastric cancer resection, first-degree relatives of gastric cancer patients, dyspeptic patients, patients with gastro-oesophageal reflux disease and non-steroidal anti-inflammatory drug users, the value of Helicobacter pylori eradication is still controversial. The regimens for first-line and second-line treatment of Helicobacter pylori infection have been recommended by the Maastricht 2 Consensus Report. Although all the treatments are considered to be effective, physicians still do not agree on what first-line regimen should be used. Furthermore, a consensus on the duration of the antibiotic treatment is still lacking, although Maastricht guidelines for treatment of Helicobacter pylori infection recommend a one-week therapy. Also regimens, as a third-line treatment, and methods to improve compliance and clinical outcome are still a matter of debate. All these points will be considered in the present review

Helicobacter pylori infection: epidemiology, pathophysiology, and therapy

Helicobacter pylori is one of the most commonly encountered human pathogens. It has been shown to be closely associated with peptic ulcer disease (PUD), gastric adenocarcinoma, and the gastric mucosa-associated lymphoid tissue (MALT) that may lead to gastric lymphoma. The current diagnostic methods include histology, microbiological culture, classic serology, urease activity detection, polymerase chain reaction (PCR) and stool antigen detection. Its treatment modality options are multiple; however, a triple regimen consisting of a proton pump inhibitor (PPI), and two antibiotics for 10 to 14 days is preferred. Drug resistance is a growing problem in this organism and new therapeutic options are currently limited.

A pilot study to determine the effectiveness of garlic oil capsules in the treatment of dyspeptic patients with Helicobacter pylori

BACKGROUND

Resistance of Helicobacter pylori to clarithromycin and metronidazole is now found worldwide. Steam-distilled garlic oil has in vitro activity against H. pylori and may be a useful alternative treatment strategy.

MATERIALS AND METHODS

In this pilot study dyspeptic patients with positive serology for H. pylori confirmed by 13C urea breath test (UBT), at 0 and 2 weeks, were enrolled. Treatment consisted of one 4 mg garlic oil capsule with a meal four times per day for 14 days. H. pylori eradication was defined as a negative UBT at both follow-up appointments. Suppression was defined as a 50% fall in 13C excess between baseline and follow-up 1.

RESULTS

Five patients completed the study. There was no evidence of either eradication or suppression of H. pylori or symptom improvement whilst taking garlic oil.

CONCLUSION

These negative results show that, within the gastric milieu, garlic oil at this dose does not inhibit H. pylori. A higher dose administered for a longer time-period may be effective. Antibiotics are usually combined with a proton-pump inhibitor or bismuth salt, as the only antibiotic with any in vivo activity against H. pylori in monotherapy is clarithromycin. A proton pump inhibitor raises gastric pH and, by increasing bacterial division, may increase the in vivo activity of garlic oil. This may be worth pursuing in a future trial.

Differentiation of metronidazole-sensitive and -resistant clinical isolates of Helicobacter pylori by immunoblotting with antisera to the RdxA protein

Antimicrobial resistance in Helicobacter pylori is a serious and increasing problem, and the development of rapid, reliable methods for detecting resistance would greatly improve the selection of antibiotics used to treat gastric infection with this organism. We assessed whether detection of the RdxA protein could provide the basis for determining the susceptibility of H. pylori to metronidazole. In order to raise polyclonal antisera to RdxA, we cloned the rdxA gene from H. pylori strain 26695 into the commercial expression vector pMAL-c2, purified the resultant fusion protein by affinity chromatography, and used this recombinant RdxA preparation to immunize rabbits. We then used this specific anti-RdxA antibody to perform immunoblotting on whole bacterial cell lysates of 17 metronidazole-sensitive and 27 metronidazole-resistant clinical isolates of H. pylori. While a 24-kDa immunoreactive band corresponding to the RdxA protein was observed in all metronidazole-sensitive strains, this band was absent in 25 of 27 resistant isolates. Our results indicate that testing for the absence of the RdxA protein would identify the majority of clinical isolates that will respond poorly to metronidazole-containing eradication regimens and have implications for the development of assays capable of detecting metronidazole resistance in H. pylori.

Helicobacter pylori antimicrobial resistance in the United Kingdom: the effect of age, sex and socio-economic status

BACKGROUND

Helicobacter pylori antimicrobial resistance is the most common reason for eradication failure. Small studies have shown metronidazole resistance to be more prevalent in certain population groups.

AIM

To determine the resistance rates in a large cohort of patients from a single centre in the UK, and to evaluate resistance patterns over time, according to age, sex and socio-economic status.

METHODS

Consecutive patients with H. pylori-positive antral gastric biopsy samples were studied from 1994 to 1999. Susceptibility testing was performed to metronidazole, tetracycline, macrolide and amoxicillin by the modified disk diffusion

METHOD

The Jarman under-privileged area score was used as a measure of socio-economic status.

RESULTS

A total of 1064 patients were studied. Overall metronidazole resistance was 40.3%, decreasing with age (P < 0.0001, odds ratio for patients over 60 years 0.63, 95% CI: 0.48-0.80). Women were more likely to have metronidazole resistant strains (P=0.003, odds ratio 1.5, 95% CI: 1.15-1.91), but there was no association with Jarman score. Macrolide resistance was associated with metronidazole resistance (P=0.03, odds ratio 2.14, 95% CI: 1.07-4.28).

CONCLUSIONS

Metronidazole resistance in H. pylori is highly prevalent and more common in women and the young, but does not appear to be related to socio-economic status.

DNA sequence analysis of rdxA and frxA from 12 pairs of metronidazole-sensitive and -resistant clinical Helicobacter pylori isolates

We previously reported that inactivation of rdxA and/or frxA converted Helicobacter pylori from metronidazole sensitive to metronidazole resistant. To examine the individual roles of rdxA and frxA in the development of metronidazole resistance in H. pylori, we examined the status of rdxA and frxA from 12 pairs of metronidazole-sensitive and -resistant H. pylori isolates obtained following unsuccessful therapy containing metronidazole. Arbitrary primed fingerprinting analyses revealed that the genotypes of 11 sensitive and resistant pairs of strains were essentially identical. Amino acid sequence identities of RdxA and FrxA from the 14 metronidazole-sensitive isolates ranged from 92 to 98% and 95 to 98%, respectively, compared to that of H. pylori J99 (MIC, 1 microg/ml). All strains with high-level metronidazole resistance (MICs, 128 microg/ml) contained premature truncation of both RdxA and FrxA caused by nonsense and/or frameshift mutations. Strains with intermediate resistance to metronidazole (MICs, 32 to 64 microg/ml) contained a single premature truncation and/or altered RdxA and FrxA caused by nonsense, frameshift, and unique missense mutations. The low-level metronidazole-resistant strains (MICs, 8 microg/ml) contained unique missense mutations in FrxA but no specific changes in RdxA. The results demonstrate that alterations in both the rdxA and frxA genes are required for moderate and high-level metronidazole resistance and that metronidazole resistance that develops during anti-H. pylori therapy containing metronidazole is most likely to involve a single sensitive strain infection rather than a coinfection with a metronidazole-resistant strain.