[Evolution of the sensitivity of 235 strains of Helicobacter pylori from 1995 to 1998 and impact of antibiotic treatment]

Antibiotic susceptibility, heteroresistance, and updated treatment strategies in Helicobacter pylori infection

In this review, we discuss the problem of antibiotic resistance, heteroresistance, the utility of cultures and antibiotic susceptibility tests in Helicobacter pylori (Hp) eradication, as well as the updated treatment strategies for this infection. The prevalence of antibiotic resistance is increasing all over the world, especially for metronidazole and clarithromycin, because of their heavy use in some geographical areas. Heteroresistance (simultaneous presence of both susceptible and resistant strains in different sites of a single stomach) is another important issue, as an isolate could be mistakenly considered susceptible if a single biopsy is used for antimicrobial tests. We also examined literature data regarding eradication success rates of culture-guided and empiric therapies. The empiric therapy and the one based on susceptibility testing, in Hp eradication, may depend on several factors such as concomitant diseases, the number of previous antibiotic treatments, differences in bacterial virulence in individuals with positive or negative cultures, together with local antibiotic resistance patterns in real-world settings. Updated treatment strategies in Hp infection presented in the guidelines of the Toronto Consensus Group (2016) are reported. These suggest to prolong eradication therapy up to 14 days, replacing the old triple therapy with a quadruple therapy based on proton pump inhibitor (PPI), bismuth, metronidazole, and tetracycline for most of the patients, or as an alternative quadruple therapy without bismuth, based on the use of PPI, amoxicillin, metronidazole, and clarithromycin. The new drug vonoprazan, a first-in-class potassium-competitive acid blocker recently approved in Japan, is also considered to be a promising solution for Hp eradication, even for clarithromycin-resistant strains. Furthermore, there is growing interest in finding new therapeutic strategies, such as the development of vaccines or the use of natural resources, including probiotics, plants, or nutraceuticals.

Review article: the global emergence of Helicobacter pylori antibiotic resistance

BACKGROUND

Helicobacter pylori is one of the most prevalent global pathogens and can lead to gastrointestinal disease including peptic ulcers, gastric marginal zone lymphoma and gastric carcinoma.

AIM

To review recent trends in H. pylori antibiotic resistance rates, and to discuss diagnostics and treatment paradigms.

METHODS

A PubMed literature search using the following keywords: Helicobacter pylori, antibiotic resistance, clarithromycin, levofloxacin, metronidazole, prevalence, susceptibility testing.

RESULTS

The prevalence of bacterial antibiotic resistance is regionally variable and appears to be markedly increasing with time in many countries. Concordantly, the antimicrobial eradication rate of H. pylori has been declining globally. In particular, clarithromycin resistance has been rapidly increasing in many countries over the past decade, with rates as high as approximately 30% in Japan and Italy, 50% in China and 40% in Turkey; whereas resistance rates are much lower in Sweden and Taiwan, at approximately 15%; there are limited data in the USA. Other antibiotics show similar trends, although less pronounced.

CONCLUSIONS

Since the choice of empiric therapies should be predicated on accurate information regarding antibiotic resistance rates, there is a critical need for determination of current rates at a local scale, and perhaps in individual patients. Such information would not only guide selection of appropriate empiric antibiotic therapy but also inform the development of better methods to identify H. pylori antibiotic resistance at diagnosis. Patient-specific tailoring of effective antibiotic treatment strategies may lead to reduced treatment failures and less antibiotic resistance.

Absence of Helicobacter pylori high tetracycline resistant 16S rDNA AGA926-928TTC genotype in gastric biopsy specimens from dyspeptic patients of a city in the interior of São Paulo, Brazil

Background

Treatment effectiveness of Helicobacter pylori varies regionally and is decreasing worldwide, principally as a result of antibiotic resistant bacterium. Tetracycline is generally included in second line H. pylori eradication regimens. In Brazil, a high level of tetracycline resistance (TetR) is mainly associated with AGA926-928TTC 16 S rDNA nucleotide substitutions. As H. pylori culture is fastidious, we investigated the primary occurrence of H. pylori 16 S rDNA high level TetR genotype using a molecular approach directly on gastric biopsies of dyspeptic patients attending consecutively at Hospital das Clinicas of Marilia, São Paulo, Brazil.

Methods

Gastric biopsy specimens of 68 peptic ulcer disease (PUD) and 327 chronic gastritis (CG) patients with a positive histological diagnosis of H. pylori were investigated for TetR 16 S rDNA genotype through a molecular assay based on amplification of a 16 S rDNA 545 bp fragment by polymerase chain reaction and HinfI restriction fragment length polymorphism (PCR/RFLP). Through this assay, AGA926-928TTC 16 S rDNA TetR genotype resulted in a three DNA fragment restriction pattern (281, 227 and 37 bp) and its absence originated two DNA fragments (264 and 281 bp) due to a 16 S rDNA conserved Hinf I restriction site.

Results

The 545 bp 16 S rDNA PCR fragment was amplified from 90% of gastric biopsies from histological H. pylori positive patients. HinfI RFLP revealed absence of the AGA926–928TTC H. pylori genotype and PCR products of two patients showed absence of the conserved 16 S rDNA HinfI restriction site. BLASTN sequence analysis of four amplicons (two conserved and two with an unpredicted HinfI restriction pattern) revealed a 99% homology to H. pylori 16 S rDNA from African, North and South American bacterial isolates. A nucleotide substitution abolished the conserved HinfI restriction site in the two PCR fragments with unpredicted HinfI RFLP, resulting in an EcoRI restriction site.

Conclusions

H. pylori AGA926-928TTC 16 S rDNA gene substitutions were not found in our population. More research is required to investigate if H. pylori TetR has a different genetic background in our region and if the nucleotide substitutions of the uncultured H. pylori 16 S rRNA partial sequences have biological significance.

Review article: the effectiveness of standard triple therapy for Helicobacter pylori has not changed over the last decade, but it is not good enough

BACKGROUND  A decrease in the Helicobacter pylori eradication rate after standard triple therapy has been suggested in recent years. AIM  To assess the efficacy of standard triple therapy in the eradication of H. pylori through an epidemiological analysis of all published Spanish trials. A secondary aim was to review the prevalence of clarithromycin resistance in Spain. METHODS  Articles on H. pylori eradication in Spain published in peer-reviewed journals were identified through MEDLINE searches. Studies that included a triple therapy consisting of any proton pump inhibitor with clarithromycin (500 mg b.d.) and amoxicillin (1 g b.d.) for up to 14 days were selected. Spanish studies evaluating the prevalence of clarithromycin resistance were also reviewed. Meta-analysis was performed using the generic inverse variance method. RESULTS The pooled eradication rates by year from Spanish studies evaluating the efficacy of the standard triple regimen revealed a relatively constant rate over the years. Overall, the analysis of the 32 studies (4727 patients) showed a mean H. pylori cure rate of 80% (95% CI = 77-82%) by intention-to-treat and 83% (81-86%) by per-protocol. When only peptic ulcer disease or 7-day regimens were considered, results were similar. Based on 13 studies (3293 patients), mean clarithromycin resistance rate was 8% (5-10%). CONCLUSION Although a decrease in the H. pylori eradication rate after triple therapy has been suggested in recent years, cure rates with this regimen did not change in Spain between 1997 and 2008. However, this by no means indicates that the efficacy of standard triple therapy in Spain is acceptable, as it has been calculated to be around only 80%. Therefore, it is evident that new strategies to improve first-line treatment are urgently needed.

Ten-day sequential treatment for Helicobacter pylori eradication in clinical practice

BACKGROUND

Cure rates of Helicobacter pylori infection with standard triple therapy are disappointingly low. A very effective, new sequential treatment schedule has recently been described. However, all studies published to date were performed in Italy; it is mandatory to confirm these results in other settings.

AIM

To assess the cure rate and the acceptability of a new sequential treatment regimen through a pilot study.

METHODS

A hundred and thirty-nine patients (60% men, mean age 49.6 +/- 15.7 yr) were recruited from six centers. H. pylori status was assessed by histology, urease test or urea breath test. Sequential regime consisted of a 10-day treatment including a proton pump inhibitor (PPI) b.d. plus amoxicillin 1 g b.d. for the first 5 days, followed by a PPI b.d. clarithromycin 500 mg b.d. and metronidazole 500 mg b.d for the next 5 days. Eradication was determined 8 wk after the end of treatment by urea breath test or histology. Eradication rates were calculated both per protocol and by intention-to-treat.

RESULTS

Eradication was achieved in 117 out of 129 patients who returned for a follow-up test. The intention-to-treat eradication rate was thus 84.2% (95%CI: 77%-90%) and the per-protocol cure rate 90.7% (95%CI: 84%-95%). The treatment was well tolerated. Only 14 patients complained of mild side effects.

CONCLUSIONS

Sequential treatment seems highly effective for eradicating H. pylori.

Comparison of three different second-line quadruple therapies including bismuth subcitrate in Turkish patients with non-ulcer dyspepsia who failed to eradicate Helicobacter pylori with a 14-day standard first-line therapy

BACKGROUND AND AIM

Many studies have reported poor results with standard first-line treatment for Helicobacter pylori. Second-line regimens that may overcome bacterial resistance can minimize side-effects and optimize compliance. The aim of this study was to evaluate the efficacy of proton pump inhibitor (PPI) and bismuth subcitrate-based quadruple therapy, after failure of a PPI plus clarithromycin and amoxicillin as first-line therapy.

METHODS

Patients who failed to eradicate the infection after initial therapy were randomly separated into three groups. The first group received lansoprazole, bismuth subcitrate, metronidazole and amoxicillin (LBMA); in the second group metronidazole was replaced by tetracycline (LBTA); and the third group was given metronidazole and tetracycline in addition to same doses of lansoprazole and bismuth subcitrate (LBMT).

RESULTS

In the LBMA group, the eradication rate was 74.7% and was significantly related to sex, with no relationship to age. In the LBTA group the eradication rate was 81.5% with similar rates in males and females. No relation to sex or age was observed. In the LBMT group the eradication rate was 82.1% with no difference between women and men and it was not related to age, either. Eradication rates in study groups were similar (P > 0.05).

CONCLUSION

A-14-day regimen of lansoprazole, bismuth subcitrate and antibiotic pairs, tetracycline-amoxicillin and tetracycline-metronidazole, is an effective quadruple therapy after one failed course of standard triple therapy. The evaluation of tolerability of and compliance with quadruple therapy needs further studies.

Seven versus ten days of rabeprazole triple therapy for Helicobacter pylori eradication: a multicenter randomized trial

BACKGROUND

Ten-day triple therapy is somewhat more effective than 7-day treatment for curing Helicobacter pylori infection. Recent studies have suggested that rabeprazole-a proton pump inhibitor with fast onset of acid inhibition-could raise the efficacy of 7-day therapies to the levels obtained with 10-day treatment.

OBJECTIVE

To compare the efficacy of 7- and 10-day rabeprazole-based triple therapy for H. pylori eradication.

PATIENTS AND METHODS

Four hundred and fifty-eight patients were randomized to 7 or 10 days of triple therapy, including rabeprazole 20 mg, clarithromycin 500 mg, and amoxicillin 1 g, all twice a day. Cure rates were evaluated by urea breath test.

RESULTS

Two hundred and thirty-seven patients received 7-day and 221 received 10-day therapy. Groups were comparable in terms of demographic variables. Intention to treat cure rates were 73.8% (95% CI: 67-79%) for 7-day and 79.6% (95%: CI:74-85%) for 10-day therapy (p= 0.09). Per-protocol cure rates were 81.8% (95% CI:76-86%) and 89.3% (95% CI: 84-93%), p= 0.02, respectively. Cure rates were similar in peptic ulcer patients but in subjects without ulcer they were clearly lower for 7-day therapy: 66%versus 77% by intention to treat (p= 0.08) and 73%versus 91% in the per-protocol analysis (p= 0.004). Side effects and compliance in the two groups were comparable.

CONCLUSIONS

Seven- and 10-day triple therapies seem equally efficient in peptic ulcer patients. In contrast, 7-day therapy is significantly less effective in nonulcer dyspepsia patients. Ten-day therapy, therefore, seems preferable when treating nonulcer patients.

[Evaluation of Helicobacter pylori susceptibility to rifaximin]

INTRODUCTION

Helicobacter pylori infection affects more than half the world's population. It is a major cause of chronic gastritis and there is a strong association with peptic ulceration and gastric adenocarcinoma. Rifaximin is a new nonabsorbable broad-spectrum antimicrobial agent that reaches high concentrations in the gastrointestinal tract.

AIM

To evaluate the in vitro activity of rifaximin against H. pylori isolates.

METHODS

Thirty-one H. pylori strains were analyzed by the agar dilution method. Clarithromycin was used as the control antibiotic. Staphylococcus aureus and Streptococcus pneumoniae were used as quality control strains. Plates were read at days 4 and 7 of incubation. The MIC50 and MIC90 of each antibiotic were calculated. Strains with a clarithromycin MIC of > 1 microg/ml were considered resistant.

RESULTS

The MIC50 of clarithromycin at days 4 and 7 was 0.125 microg/ml and the MIC90 at days 4 and 7 ranged from 8 to 16 microg/ml, respectively. The MIC50 of rifaximin at days 4 and 7 ranged from 1 to 2 microg/ml, respectively, and the MIC90 was 4 microg/ml at both days 4 and 7. Twenty percent of H. pylori strains were resistant to clarithromycin. All clarithromycin-resistant strains were inhibited at a maximal rifaximin concentration of 4 microg/ml.

CONCLUSION

These results indicate that this new antibiotic may be useful for eradication of H. pylori infection. Because rifaximin is active against H. pylori strains resistant to clarithromycin, it could be useful in combination with this drug or in the treatment of therapeutic failure.

Ranitidine-bismuth citrate, tetracycline and metronidazole followed by triple therapy as alternative strategy for Helicobacter pylori treatment: a pilot study

BACKGROUND

Eradication rates of triple therapy--a proton pump inhibitor, clarithromycin and amoxicillin twice daily for 7 days--are suboptimal in some areas of the world. Triple therapy combining ranitidine-bismuth citrate, tetracycline and metronidazole is a very effective second-line therapy. Management strategies including this treatment as first-line therapy may represent a reasonable choice.

AIM

To evaluate the efficacy of a strategy combining ranitidine-bismuth citrate triple therapy followed by a proton pump inhibitor-based triple therapy for Helicobacter pylori eradication in a pilot study.

PATIENTS AND METHODS

One hundred and thirty-six consecutive H. pylori-positive patients were treated with 400 mg ranitidine-bismuth citrate twice daily, 500 mg tetracycline three times daily and 500 mg metronidazole three times daily for 7 days. Second-line therapy consisted of 20 mg omeprazole twice daily, 500 mg clarithromycin twice daily and 1 g amoxicillin twice daily for 7 days. The efficacy of the treatment was evaluated by histology or the urea breath test.

RESULTS

Cure rates were 109/136 patients [80.2%; 95% confidence interval (CI), 72-86%] by intention to treat and 109/127 (85.8%; 95% CI, 78-91%) per protocol. Fifteen of the patients with treatment failure received second-line treatment. Cure rates for the strategy as a whole were 119/136 (87.5%; 95% CI, 81-92%) by intention to treat and 119/123 (96.8%; 95% CI, 92-99%) per protocol.

CONCLUSIONS

The strategy achieves good eradication rates. As the first-line therapy avoids the use of clarithromycin, it could be useful in areas where high resistance to this antibiotic lead to poor results with triple therapy.

Emergence of tetracycline resistance in Helicobacter pylori: multiple mutational changes in 16S ribosomal DNA and other genetic loci

Tetracycline is useful in combination therapies against the gastric pathogen Helicobacter pylori. We found 6 tetracycline-resistant (Tet(r)) strains among 159 clinical isolates (from El Salvador, Lithuania, and India) and obtained the following four results: (i) 5 of 6 Tet(r) isolates contained one or two nucleotide substitutions in one part of the primary tetracycline binding site in 16S rRNA (AGA(965-967) [Escherichia coli coordinates] changed to gGA, AGc, guA, or gGc [lowercase letters are used to represent the base changes]), whereas the sixth (isolate Ind75) retained AGA(965-967); (ii) PCR products containing mutant 16S ribosomal DNA (rDNA) alleles transformed recipient strains to Tet(r) phenotypes, but transformants containing alleles with single substitutions (gGA and AGc) were less resistant than their Tet(r) parents; (iii) each of 10 Tet(r) mutants of reference strain 26695 (in which mutations were induced with metronidazole, a mutagenic anti-H. pylori agent) contained the normal AGA(965-967) sequence; and (iv) transformant derivatives of Ind75 and of one of the Tet(r) 26695 mutants that had acquired mutant rDNA alleles were resistant to tetracycline at levels higher than those to which either parent strain was resistant. Thus, tetracycline resistance in H. pylori results from an accumulation of changes that may affect tetracycline-ribosome affinity and/or other functions (perhaps porins or efflux pumps). We suggest that the rarity of tetracycline resistance among clinical isolates reflects this need for multiple mutations and perhaps also the deleterious effects of such mutations on fitness. Formally equivalent mutations with small but additive effects are postulated to contribute importantly to traits such as host specificity and virulence and to H. pylori's great genetic diversity.