Review article: nitroimidazole resistance in Helicobacter pylori

Anti-toxoplasma activity and DNA-binding of copper(II) and zinc(II) coordination compounds with 5-nitroimidazole-based ligands

Tetrahedral copper(II) and zinc(II) coordination compounds from 5-nitroimidazole derivatives, viz. 1-(2-chloroethyl)-2-methyl-5-nitroimidazole (cenz) and ornidazole 1-(3-chloro-2-hydroxypropyl)-2-methyl-5-nitroimidazole (onz), were synthesized and spectroscopically characterized. Their molecular structures were determined by X-ray diffraction studies. The complexes [Cu(onz)2X2], [Zn(onz)2X2], [Cu(cenz)2X2] and [Zn(cenz)2X2] (X- = Cl, Br), are stable in solution and exhibit positive LogD7.4 values that are in the range for molecules capable of crossing the cell membrane via passive difussion. Their biological activity against Toxoplasma gondi was investigated, and IC50 and lethal dose (LD50) values were determined. The ornidazole copper(II) compounds showed very good antiparasitic activity in its tachyzoite morphology. The interaction of the coordination compounds with DNA was examined by circular dichroism, fluorescence (using intercalating ethidium bromide and minor groove binding Hoechst 33258) and UV-Vis spectroscopy. The copper(II) compounds interact with the minor groove of the biomolecule, whereas weaker electrostatic interactions take place with the zinc(II) compounds. The spectroscopic data achieved for the two series of complexes (namely with copper(II) and zinc(II) as metal center) agree with the respective DNA-damage features observed by gel electrophoresis.

Helicobacter pylori diagnosis and therapy in the era of antimicrobial stewardship

The diagnosis and therapy of Helicobacter pylori infection have undergone major changes based on the use the principles of antimicrobial stewardship and increased availability of susceptibility profiling. H. pylori gastritis now recognized as an infectious disease, as such there is no placebo response allowing outcome to be assessed in relation to the theoretically obtainable cure rate of 100%. The recent recognition of H. pylori as an infectious disease has changed the focus to therapies optimized to reliably achieve high cure rates. Increasing antimicrobial resistance has also led to restriction of clarithromycin, levofloxacin, or metronidazole to susceptibility-based therapies. Covid-19 resulted in the almost universal availability of polymerase chain reaction testing in hospitals which can be repurposed to utilize readily available kits to provide rapid and inexpensive detection of clarithromycin resistance. In the United States, major diagnostic laboratories now offer H. pylori culture and susceptibility testing and American Molecular Laboratories offers next-generation sequencing susceptibility profiling of gastric biopsies or stools for the six commonly used antibiotics without need for endoscopy. Current treatment recommendations include (a) only use therapies that are reliably highly effective locally, (b) always perform a test-of-cure, and (c) use that data to confirm local effectiveness and share the results to inform the community regarding which therapies are effective and which are not. Empiric therapy should be restricted to those proven highly effective locally. The most common choices are 14-day bismuth quadruple therapy and rifabutin triple therapy. Prior guidelines and treatment recommendations should only be used if proven locally highly effective.

Appropriateness of Repeating Helicobacter pylori Culture and Susceptibility Testing Following Failure of Individualized Antibiotic Therapy

BACKGROUND

Current guidelines recommend direct Helicobacter pylori culture and antibiotic susceptibility testing following 2 failed eradication attempts. If this process is followed and yet subsequent treatment is unsuccessful, it is unclear whether susceptibility testing should be repeated. This is the first study to examine the appropriateness of repeated H. pylori culture and susceptibility testing following failure of individualized treatment.

METHODS

Between 2007 and 2014, consecutive patients who underwent at least 2 upper gastrointestinal endoscopies with H. pylori culture and susceptibility testing at our institution following several treatment failures were retrospectively identified. Antibiotic susceptibility was recorded and linked to demographic data.

RESULTS

A total of 68 cultures from 34 patients were included (12 (35.3%) men, 41.4 ± 16.6 years), and 20 (58.8%) cultures had a different antibiotic susceptibility profile on repeat testing (8 (23.5%) with new susceptibility and 13 (38.2%) with new resistance). Acquired resistance to clarithromycin, levofloxacin and metronidazole was observed in 9 (26.5%), 2 (5.9%) and 10 (29.4%) cultures, respectively. Subjects with resistance to ≤1 antibiotic at baseline were more likely to develop resistance to at least 1 antibiotic on subsequent culture, compared to subjects with resistance to ≥2 antibiotics at baseline (13 (100%) vs. 5 (23.8%), p < 0.01).

CONCLUSION

Repeating H. pylori culture and susceptibility testing usually yields new antimicrobial susceptibility data. However, the clinical usefulness of this approach remains unclear.

Helicobacter pylori binding to new glycans based on N-acetyllactosamine

Previously we reported binding of Helicobacter pylori to various nonacid and sialylated neolacto carbohydrate structures using a wide range of natural and chemically modified sequences. A novel nonsialylated neolacto-based binding epitope, GlcNAc beta 3Gal beta 4GlcNAc, and analogous structures carrying terminal GalNAc beta 3, GalNAc alpha 3, or Gal alpha 3 showed the binding activity (Miller-Podraza H, Lanne B, Angström J, Teneberg S, Abul-Milh M, Jovall P-A, Karlsson H, Karlsson K-A. 2005. Novel binding epitope for Helicobacter pylori found in neolacto carbohydrate chains. J Biol Chem. 280:19695-19703). The present work reports two other H. pylori-binding nonsialylated neolacto-based structures, GlcA beta 3Gal beta 4GlcNAc beta 3-R and Glc beta 3Gal beta 4GlcNAc beta 3-R, and two amide derivatives (N-methyl and N-ethyl) of GlcA beta 3Gal beta 4GlcNAc beta 3-R which were bound by H. pylori. The latter structures turned out to be more effective as H. pylori binders than the parent saccharide. New reducing-end variants of the neolacto epitope including species containing N-acetyllactosamine linked beta 6 to GlcNAc or Gal with similarity to branched polylactosamines and mucins were prepared and tested. The results extend our previous findings on binding specificities of H. pylori and show that this pathogen is able to interact with an array of N-acetyllactosamine/neolacto structures, which may be of importance for the in vivo interaction of the bacterium with human cells. The information gained in this work may also be of value for rational design of anti-H. pylori drugs.

Helicobacter pylori and antimicrobial resistance: molecular mechanisms and clinical implications

Helicobacter pylori is an important human pathogen that colonises the stomach of about half of the world's population. The bacterium has now been accepted as the causative agent of several gastroduodenal disorders, ranging from chronic active gastritis and peptic ulcer disease to gastric cancer. The recognition of H pylori as a gastric pathogen has had a substantial effect on gastroenterological practice, since many untreatable gastroduodenal disorders with uncertain cause became curable infectious diseases. Treatment of H pylori infection results in ulcer healing and can reduce the risk of gastric cancer development. Although H pylori is susceptible to many antibiotics in vitro, only a few antibiotics can be used in vivo to cure the infection. The frequent indication for anti-H pylori therapy, together with the limited choice of antibiotics, has resulted in the development of antibiotic resistance in H pylori, which substantially impairs the treatment of H pylori-associated disorders. Antimicrobial resistance in H pylori is widespread, and although the prevalence of antimicrobial resistance shows regional variation per antibiotic, it can be as high as 95%. We focus on the treatment of H pylori infection and on the clinical relevance, mechanisms, and diagnosis of antimicrobial resistance.

Interaction of Helicobacter pylori with sialylated carbohydrates: the dependence on different parts of the binding trisaccharide Neu5Acα3Galβ4GlcNAc

We have recently shown that binding of Helicobacter pylori to sialylated carbohydrates is dependent on the presence of the carboxyl group and the glycerol chain of Neu5Ac. In this work we investigated the importance of GlcNAc in the binding trisaccharide Neu5Acalpha3Galbeta4GlcNAc and the role of the N-acetamido groups of both Neu5Ac and GlcNAc. An important part of the project was epitope dissection, that is chemical derivatizations of the active carbohydrate followed by binding studies. In addition we used a panel of various unmodified carbohydrate structures in the form of free oligosaccharides or glycolipids. These were tested for binding by hemagglutination inhibition assay, TLC overlay tests, and a new quantitative approach using radiolabeled neoglycoproteins. The studies showed that the N-acetamido group of Neu5Ac is important for binding by H. pylori, whereas the same group of GlcNAc is not. In addition, Fuc attached to GlcNAc, as tested with sialyl-Lewis x, did not affect the binding. Free Neu5Ac was inactive as inhibitor, and Neu5Acalpha3Gal turned out to be active. The binding preference for neolacto structures was confirmed, although one strain also was inhibited by lacto chains. The combined results revealed that an intact Neu5Ac is crucial for the interactions with H. pylori. Parts of Gal also seem to be necessary, whereas the role of the GlcNAc is secondary. GlcNAc does influence binding, however, primarily serving as a guiding carrier for the binding epitope rather than being a part of the binding structure.

Pantoprazole in severe acid-peptic disease: the effectiveness and safety of 5 years' continuous treatment

OBJECTIVE

This is our final report on the clinical effectiveness and safety of long-term pantoprazole in patients with severe peptic ulcer or reflux disease during continuous treatment for up to 5 years.

METHODS

Patients (n= 150) with peptic ulcer or reflux erosive oesophagitis running an aggressive course or with complications, and refractory to H2-receptor antagonists, were entered into this 5-year programme. Assessment was by serial endoscopy, clinical examination, serum gastrin estimation, gastric mucosal histology and mucosal endocrine cell quantification.

RESULTS

Healing results were presented earlier. The estimated rates of remission on maintenance treatment with pantoprazole (n = 115) were 82% at 1 year, 75% at 2 years, 72% at 3 years, 70% at 4 years and 68% at 5 years. Helicobacter pylori infection appeared not to influence the outcome in reflux patients, with roughly two-thirds continuing in remission irrespective of infection. Only four patients had adverse events considered to be definitely related to pantoprazole. Median gastrin levels rose by 1.5-2-fold and were higher in those with H. pylori infection; 13 patients had levels >500 ng/L on at least one occasion, but these high levels were not sustained. Histological changes were more marked in patients infected with H. pylori: chronic gastritis decreased in the antrum and increased in the corpus, which also showed atrophic changes. The total number of endocrine cells in the antrum showed little variation over 60 months but fell by around one-third in the corpus.

CONCLUSION

Long-term treatment with pantoprazole is effective and safe.

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.

Pretreatment antimicrobial susceptibility testing is cost saving in the eradication of Helicobacter pylori

BACKGROUND & AIMS

The major obstacle to 100% effective eradication of Helicobacter pylori infection is represented by antimicrobial-resistant H. pylori strains. This randomized study was designed to evaluate whether regimens based on pretreatment susceptibility testing were more effective and cost saving compared with standard nonsusceptibility testing-based therapy in the eradication of H. pylori infection.

METHODS

We studied 150 consecutive H. pylori-infected dyspeptic subjects. Patients were randomly assigned to omeprazole 20 mg twice daily, clarithromycin 500 mg twice daily, and metronidazole 500 mg twice daily for 7 days or to omeprazole 20 mg twice daily and 2 antimicrobials chosen based on susceptibility testing. H. pylori status was reevaluated 12 weeks after the end of treatment by the (13)C-urea breath test.

RESULTS

Susceptibility testing-based regimens led to the following results. (1) Eradication rates were 97.3% (95% confidence interval [CI], 91.2%-99.5%) (71 of 73) and 94.6% (95% CI, 87.6%-98.3%) (71 of 75) in the per-protocol and intention-to-treat analysis, respectively. These were significantly higher (P < 0.005) than eradication rates obtained without susceptibility testing, that is, 79.4% (95% CI, 69.1%-87.6%) (58 of 73) and 77.3% (95% CI, 66.9%-85.7%) (58 of 75) in the per-protocol and intention-to-treat analyses, respectively. (2) There were savings of approximately $5 U.S. per patient compared with standard triple therapy.

CONCLUSIONS

Pretreatment antimicrobial susceptibility testing is more effective and cost saving and, in health systems that confirm cost advantage, microbial susceptibility testing should be routinely used for eradication of H. pylori infection.

Analysis of the rdxA gene in high-level metronidazole-resistant clinical isolates confirms a limited use of rdxA mutations as a marker for prediction of metronidazole resistance in Helicobacter pylori

Metronidazole (Mtz) resistance in the gastric pathogen Helicobacter pylori is closely associated with inactivation of the nitroreductase gene rdxA. In order to identify respective mutations for diagnostic purposes we analyzed the rdxA gene in a collection of high-level Mtz-resistant clinical H. pylori isolates. Size alterations in the rdxA gene region were found in only two out of 45 and one out of 40 isolates showing lower-level (minimal inhibitory concentrations (MICs) 32-192 microg ml(-1)) and high-level (MIC>/=256 microg ml(-1)) Mtz resistance, respectively. Point mutations that interrupt the rdxA reading frame were detected in two out of eight high-level resistant isolates (MICs>/=256 microg ml(-1)). Most remarkably, the rdxA gene sequence was found to be identical in four out of five high-level Mtz-resistant and -susceptible paired H. pylori isolates from the same patients each. Taken together, these results demonstrate that although some isolates carry classical resistance-associated rdxA mutations, as described earlier, the use of rdxA mutations as a marker for prediction of Mtz resistance is limited.

Antibacterial actions of fatty acids and monoglycerides against Helicobacter pylori

The bactericidal potencies of saturated and unsaturated fatty acids (FAs) and monoglycerides (MGs) against Helicobacter pylori were determined following short incubations with freshly harvested cells over a range of pHs. FAs and their derivatives with an equivalent-carbon number of 12 were the most potent: lauric acid had a minimum bactericidal concentration (MBC) at pH 7.4 of 1 mM, myristoleic and linolenic acid were the most potent unsaturated FAs (MBCs of 0.5 mM, pH 7.4), and monolaurin was the most potent MG (MBC 0.5 mM). Potencies of saturated FAs were increased sharply by lowering pH, and a decrease of only 0.5 pH units can cause a change from non-lethal to lethal conditions. Conversely, the bactericidal action of monolaurin was not pH-dependent. The bactericidal potencies of unsaturated FAs increased with degree of unsaturation. When more than one FA or FA plus MGs were present, their combined action was additive. Urea and endogenous urease did not protect H. pylori from the bactericidal action of FAs. These results suggest that H. pylori present in the stomach contents (but not necessarily within the mucus barrier) should be rapidly killed by the millimolar concentrations of FAs and MGs that are produced by pre-intestinal lipase(s) acting on suitable triglycerides such as milk fat.

Has education about Helicobacter pylori infection been effective? Worldwide survey of primary care physicians

BACKGROUND

Confusion exists among physicians about the management of Helicobacter pylori (H. pylori) infection. We aimed to survey primary care physicians' (PCP) knowledge and management of H. pylori-related diseases.

METHODS

Four-hundred and seventy randomly selected PCP from 29 countries were surveyed.

RESULTS

The pathological role of H. pylori was of less concern in South Africa than the rest of the world (63% compared to 93%). The causal relationship between H. pylori and gastric and duodenal ulcers and gastric cancer was accepted by 81%, 85%, and 61% of respondents, respectively. Endoscopy was used by 62% of respondents to diagnose the infection. Histology was used by 61% of European participants for diagnosis compared to 3% in North American and 0% in South Africa. Proton-pump inhibitor (PPI)-based triple therapies were prescribed by 89% of respondents. Physicians in Oceania (35%) and South Africa (45%) were less concerned about bacterial resistance than respondents elsewhere. Sixty-three percent of respondents considered H. pylori relevant to dyspepsia management and 66% treated new dyspepsia empirically, compared to 18% who chose endoscopic diagnosis and 13% who used a H. pylori test and treat strategy. For persistent or recurrent infection, 56% of South African physicians treated with another regimen compared to 33% of PCP from elsewhere. Ninety-one percent of European participants agreed that current information on H. pylori management is helpful and 68% of PCP from other regions considered the information to be adequate.

CONCLUSIONS

Current guidelines on the management of H. pylori infection have been useful for PCP worldwide. Contrasting answers to some questions may reflect differences in health care systems, epidemiology and approaches to the management of H. pylori infection between countries.

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.

Levofloxacin based regimens for the eradication of Helicobacter pylori

BACKGROUND

A 7 day treatment scheme based on rabeprazole/levofloxacin/amoxycillin or tinidazole achieved an eradication rate over 90%. However, the combination of drugs and duration of treatment for the correct use of levofloxacin in the eradication of are still unclear.

OBJECTIVE

To compare the efficacy and tolerability of rabeprazole/levofloxacin based dual therapies given for 5, 7 or 10 days with rabeprazole/levofloxacin/amoxycillin triple therapy for 7 days.

METHODS

One hundred and sixty patients with infection documented by the C-urea breath test and histology were included in this prospective, open label study. Subjects were randomized in four groups: (1) levofloxacin (500 mg o.d.), amoxycillin (1 g b.d.) and rabeprazole (20 mg o.d.) for 7 days; (2) levofloxacin (500 mg o.d.) and rabeprazole (20 mg o.d.) for 5 days; (3) levofloxacin (500 mg o.d.) and rabeprazole (20 mg o.d.) for 7 days; and (4) levofloxacin (500 mg o.d.) and rabeprazole (20 mg o.d.) for 10 days. Six weeks after the end of therapy status was checked by using the C-urea breath test.

RESULTS

All patients completed the therapeutic regimens. The eradication rate was not significantly modified by treatment duration in the dual therapy schemes (5 days: 20/40, 50%; 7 days: 28/40, 70%; 10 days: 26/40, 65%). The eradication rate of the 1 week levofloxacin based triple therapy was significantly higher than that observed using any dual therapies (36/40). No major adverse effects were observed.

CONCLUSIONS

A rabeprazole/levofloxacin dual eradication regimen is simple and well tolerated but does not achieve an acceptable eradication rate when compared to a 1 week rabeprazole/levofloxacin/amoxycillin triple therapy. The eradication rate did not increase with a longer regimen.

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.

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.

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.

Efficacy of low-dose clarithromycin triple therapy and tinidazole-containing triple therapy for Helicobacter pylori eradication

BACKGROUND

Proton pump inhibitor-based triple therapies are recommended as the first-line treatment for Helicobacter pylori eradication.

AIM

To evaluate the efficacies of low-dose clarithromycin triple therapy and tinidazole-containing triple therapy in a metronidazole resistance prevalent area and to compare the efficacies with standard triple therapy.

METHODS

In a randomized, multicentre, prospective study, a total of 352 patients with duodenal ulcer or non-ulcer dyspepsia were randomly divided into three groups according to the administered regimen: OAC250 group (omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 250 mg), OAC500 group (omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg) and OTC group (omeprazole, 20 mg, tinidazole, 500 mg, and clarithromycin, 500 mg). The three groups received each regimen twice daily for 7 days. Upper gastrointestinal endoscopy was performed before and 4 weeks after treatment. H. pylori status was determined by rapid urease test and 13C urea breath test.

RESULTS

The eradication rates in the OAC250, OAC500 and OTC groups were 76.2%, 65.7% and 64.8% (95% confidence interval: 67.9-84.4%, 56.7-74.8% and 55.7-73.9%), respectively, by intention-to-treat analysis (P=0.149) and 92.8%, 87.2% and 84.1% (95% confidence interval: 84.4-97.3%, 77.9-93.8% and 73.9-91.2%), respectively, by per protocol analysis (P=0.088). All regimens were well tolerated and compliance was excellent.

CONCLUSIONS

Both low-dose clarithromycin triple therapy and tinidazole-containing triple therapy are effective and safe regimens for H. pylori eradication.

Twelve year observation of primary and secondary antibiotic-resistant Helicobacter pylori strains in children

BACKGROUND

The effectiveness of Helicobacter pylori eradication regimens is influenced by antibiotic susceptibility of infecting strains. Data concerning antibiotic resistance in children are limited. We report the evolution of primary and secondary resistance in a series of Belgian children during the last 12 years.

PATIENTS AND METHODS

From 1989 through 2000, H. pylori gastritis was diagnosed in 569 children, and antibiotic susceptibility tests were performed in 555. Eradication, using different schemes, failed in 128 of 457 treated children. After eradication failure antibiotic susceptibility determination was performed in 87 of 128. Comparison of antibiotic susceptibility of strains isolated from the gastric body and from the antrum was performed in 238 samples.

RESULTS

Resistance to amoxicillin was not observed. The rate of primary resistance to nitroimidazole derivatives was 18.0% (101 of 555) and remained constant throughout this period, whereas primary resistance to macrolides increased from an average of 6.0% (range, 0 to 10%) before 1995 to 16.6% (range, 10 to 25%, P < 0.001) thereafter. Antibiotic consumption in Belgium, especially macrolides, did not show important fluctuations during the study period. Secondary resistance developed in 39 of 87 patients (46%). Strains isolated from different gastric locations show identical susceptibility testing in all but 5 of 238.

CONCLUSIONS

Resistance of H. pylori to macrolides increased in our pediatric population which did not appear to correlate with macrolides prescription habits in our country. After eradication failure acquired secondary resistance was observed in one-half of the patients.

Outcomes of Helicobacter pylori treatment in community practice and impact of therapeutic effectiveness information on physician behaviour

BACKGROUND

The effect of knowledge of Helicobacter pylori eradication rates on physician choice of treatment regimen is unknown. As practice variation results in differences in outcome, it is important to determine whether physician behaviour can be altered by such knowledge.

AIMS

(i) To determine whether dissemination of practice variation and effectiveness data regarding H. pylori changes subsequent prescribing behaviour and (ii) whether this change results in an improvement in the effectiveness of therapy.

METHODS

Community gastroenterologists in the Portland metropolitan area enrolled patients being treated for H. pylori. The regimen used, diagnostic method, indication and success in eradication was measured. Patient-centred factors were also measured, including symptoms, interest in post-treatment diagnostic testing and willingness to pay.

RESULTS

Significantly more physicians participating in both studies used proton pump inhibitor-triple therapy based regimens in this trial (46% vs. 85%, P=0.01), although the overall difference between the two trials was not significant (62% vs. 83%, P=0.11). There was no change in overall eradication rates by per protocol analysis between trials (84% vs. 85%, P=0.78), but a significant decrease in effectiveness by intention-to-treat analysis observed in this study (80% vs. 71%, P=0.03). Significantly more patients were treated for reasons other than peptic ulcer disease in this study (P=0.0003).

CONCLUSIONS

The overall effectiveness of H. pylori therapy in practice remains good. There has been a shift in the choice of treatment regimen and indication for therapy between the time periods of the two studies. Dissemination of treatment data appears to effect prescribing behaviour, but whether it has a beneficial effect on treatment outcome remains unproven.

Increasing multidrug resistance in Helicobacter pylori strains isolated from children and adults in Mexico

The susceptibilities to three antimicrobials of 195 Helicobacter pylori strains isolated from Mexican patients is reported; 80% of the strains were resistant to metronidazole, 24% were resistant to clarithromycin, and 18% presented a transient resistance to amoxicillin. Resistance to two or more antimicrobials increased significantly from 1995 to 1997.

One-week ranitidine bismuth citrate-based triple therapy for the eradication of Helicobacter pylori in Hong Kong with high prevalence of metronidazole resistance

AIM

To compare 1-week ranitidine bismuth citrate-based (RBC) triple therapy vs. omeprazole-based (O) triple therapy for the eradication of Helicobacter pylori infection in Hong Kong with high prevalence of metronidazole resistance.

METHODS

Patients with non-ulcer dyspepsia and H. pylori infection were randomized to receive either: (i) RBCCM: ranitidine bismuth citrate (pylorid) 400 mg, clarithromycin 250 mg and metronidazole 400 mg; or (ii) OCM: omeprazole 20 mg, clarithromycin 250 mg and metronidazole 400 mg, each given twice daily for 1 week. Endoscopy (CLO test, histology and culture) and 13C-urea breath test were performed before randomization and 6 weeks after drug treatment.

RESULTS

A total of 180 patients were randomized. H. pylori eradication rates (intention-to-treat, n=180/per protocol, n=166) were 83%/92% for RBCCM and 66%/70% for OCM (P=0.01, intention-to-treat and P=0.001, per protocol, respectively). RBCCM treatment was unaffected by metronidazole susceptibility and achieved a significantly higher eradication rate in metronidazole-resistant cases (89%) than the OCM group (45%, P=0.0064).

CONCLUSION

One-week ranitidine bismuth citrate-based triple therapy is significantly better than omeprazole-based triple therapy for the eradication of H. pylori infection, especially in metronidazole-resistant cases. It is an effective regimen for the eradication of H. pylori infection in regions with a high prevalence of metronidazole resistance.

Distinctiveness of genotypes of Helicobacter pylori in Calcutta, India

The genotypes of 78 strains of Helicobacter pylori from Calcutta, India (55 from ulcer patients and 23 from more-benign infections), were studied, with a focus on putative virulence genes and neutral DNA markers that were likely to be phylogenetically informative. PCR tests indicated that 80 to 90% of Calcutta strains carried the cag pathogenicity island (PAI) and potentially toxigenic vacAs1 alleles of the vacuolating cytotoxin gene (vacA), independent of disease status. This was higher than in the West (where cag PAI(+) vacAs1 genotypes are disease associated) but lower than in east Asia. The iceA2 gene was weakly disease associated in Calcutta, whereas in the West the alternative but unrelated iceA1 gene at the same locus is weakly disease associated. DNA sequence motifs of vacAm1 (middle region) alleles formed a cluster that was distinct from those of east Asia and the West, whereas the cagA sequences of Calcutta and Western strains were closely related. An internal deletion found in 20% of Calcutta iceA1 genes was not seen in any of approximately 200 strains studied from other geographic regions and thus seemed to be unique to this H. pylori population. Two mobile DNAs that were rare in east Asian strains were also common in Calcutta. About 90% of Calcutta strains were metronidazole resistant. These findings support the idea that H. pylori gene pools differ regionally and emphasize the potential importance of studies of Indian and other non-Western H. pylori populations in developing a global understanding of this gastric pathogen and associated disease.