Antibiotic resistance in Helicobacter pylori

Epidemiology of Helicobacter pylori in Australia: a scoping review

Background

Helicobacter pylori (H. pylori), a bacterium implicated in the development of peptic ulcer and gastric cancer, is estimated to infect around half the world's population. Its prevalence in Australia is unclear. This scoping review aimed to evaluate all Australian literature providing estimates of the prevalence of H. pylori.

Methods

Australian studies examining H. pylori prevalence from 1982 onwards were eligible for inclusion. Medline, Embase and Scopus databases, and grey literature sources, were searched. Two independent reviewers undertook a two-stage screening process. Data were extracted by two independent reviewers using a pre-specified template.

Results

Of 444 identified studies, 75 were included in the review. H. pylori prevalence in Australian population-based studies (n = 8) ranged from 38.0% in 1991 to 15.1% in 2002; however, estimated prevalence across all non-clinical population studies in diverse sub-groups (n = 29) has varied dramatically. Decreased prevalence has been more marked in populations with gastrointestinal symptoms and conditions compared to non-clinical populations. Data on H. pyloriprevalence in vulnerable populations are lacking.

Conclusions

This is the first scoping review of Australian studies reporting H. pylori prevalence. A wide range of study designs, population groups, geographic regions, and diagnostic methods was included, involving data collected over a 50-year period (1969 to 2018). The summary of H. pylori prevalence estimates over time in this review points to a decrease in prevalence in Australia, particularly among populations with gastrointestinal symptoms and illnesses; however, it is unknown whether there is inequity in prevalence trends across vulnerable sub-groups of the Australian population. Future research and interventions supporting the health and wellbeing of vulnerable populations is required to ensure equitable health gains are made for all.

Increasing Helicobacter pylori clarithromycin resistance in Australia over 20 years

OBJECTIVES

Helicobacter pylori infection is responsible for considerable morbidity and mortality worldwide, and eradication rates are falling in many countries, primarily due to clarithromycin and metronidazole resistance. However, there is a paucity of contemporary Australian data, which we sought to address by evaluating local rates of resistance of H. pylori to amoxicillin, clarithromycin, metronidazole, and tetracycline over the past 20 years.

DESIGN

All gastric biopsy specimens collected at endoscopy to detect H. pylori infection at a single centre underwent routine culture and antibiotic susceptibility testing between 1998-2017. Specimens from 12,842 patients were cultured for H. pylori, of which 1,473 positive cultures were tested for antibiotic susceptibility.

RESULTS

Antibiotic resistance to clarithromycin increased by 3.7% per year (IRR 1.037, p=0.014) over 20 years, with a corresponding 5.0% annual increase in minimum inhibitory concentration (MIC) (OR 1.050, p<0.001). Since 2010, average clarithromycin resistance has exceeded 20%, with >25% of isolates resistant in the last 2 years of data capture. By contrast, rates of resistance to metronidazole (35.3%), amoxicillin (0.14%) and tetracycline (0.34%) and their MICs have remained stable. Review of a representative sample of these patients (n=120, 8%) revealed that only 5% had documented prior H. pylori eradication therapy.

CONCLUSIONS

Over the last 20 years there has been a substantial rise in clarithromycin resistance, with stable metronidazole resistance and low rates of resistance to amoxicillin and tetracycline. Current first line H. pylori eradication therapy may fail to achieve adequate eradication rates, and optimal first line therapy in Australia should be revisited. This article is protected by copyright. All rights reserved.

Antibiotic resistance of Helicobacter pylori in Australia and New Zealand: A systematic review and meta-analysis

OBJECTIVE

While the global prevalence of antibiotic-resistant Helicobacter pylori (H. pylori) is increasing, there is much regional variation, and local data are required to guide eradication therapy. We performed a systematic review and meta-analysis to determine rates of H. pylori antibiotic resistance in Australia and New Zealand.

STUDY DESIGN

Random effects meta-analysis of data from 15 published studies and three published abstracts reporting prevalence of primary or secondary H. pylori antibiotic resistance in Australasia.

DATA SOURCES

PubMed, EMBASE, MEDLINE, PROSPERO, and the Cochrane Library were searched until August, 2020.

DATA SYNTHESIS

Fifteen published studies and three published abstracts were identified; one study was excluded due to high risk of bias. Seventeen studies conducted between 1996 and 2013 were included in the final analysis, 12 reporting primary and five reporting secondary antibiotic resistance. Prevalence of primary resistance was clarithromycin 7.4% (95% confidence interval [CI], 5.3-9.7%), metronidazole 50.0% (95%CI, 23.9-56.1%), fluoroquinolones 3.7% (95%CI, 0.004-14.8%), and both amoxicillin and tetracycline <0.5%. Subgroup analysis (last 20 years) showed doubling of clarithromycin resistance to 16.1% (95%CI 11.2-21.7%) with other resistance stable. Prevalence of secondary resistance was high for all antibiotics, particularly clarithromycin 78.7% (95%CI, 64.1-90.1%) and metronidazole 68.3% (95%CI, 59.9-76.1%).

CONCLUSIONS

The outcomes reveal an increase in primary H. pylori clarithromycin resistance since the year 2000, while metronidazole resistance has remained stable and primary resistance to amoxicillin, tetracycline, and fluoroquinolones is low. Rates of secondary resistance to metronidazole and clarithromycin are high. The results highlight the need for contemporary local data on antibiotic resistance in Australia and New Zealand.

Helicobacter pylori antimicrobial resistance in Melbourne, Australia. Time to review therapeutic guidelines?

BACKGROUND

Antimicrobial resistance (AMR) in Helicobacter pylori is a global concern. The AMR data to inform the Australian Therapeutic Guidelines is based upon data over 20 years old.

AIMS

To evaluate the frequency of antimicrobial resistance in H. pylori isolates from gastric biopsy specimens received in our laboratory in Melbourne, Australia To review the literature on resistance rates in Australia and compare historic data.

METHODS

A retrospective, observational study summarising AMR rates in all H. pylori isolates from our laboratory from 2015 to June 2020.

SETTING

Microbiology laboratory in metropolitan Melbourne, Australia, receiving referrals from private hospitals, gastroenterology clinics, and endoscopy suites.

OUTCOME MEASURES

Population minimum inhibitory concentration distributions and frequency of resistance to clarithromycin, amoxicillin, metronidazole, and tetracycline in H. pylori isolates.

RESULTS

386 H. pylori isolates with susceptibility testing data were identified. The frequency of resistance in this cohort was: clarithromycin 89.9%, amoxicillin 23.5%, metronidazole 66.1%, and tetracycline 4.4%. Comparison with historical data may suggest increasing AMR rates in Australia. Main limitation is lack of treatment history to correlate AMR results.

CONCLUSIONS

Definitive conclusions from this cohort cannot be made, but trends suggest rising levels of primary H. pylori AMR rates in Australia. This has important implications for empirical treatment decision making and treatment outcomes. Primary H. pylori AMR requires dedicated studies and current Australian therapeutic guideline recommendations may require re-evaluation. We propose considerations for improving the management of H. pylori in Australia. A centralised public health approach to H. pylori AMR surveillance should be established. This article is protected by copyright. All rights reserved.

A Newly Discovered Drug Resistance Gene rfaF In Helicobacter pylori

BACKGROUND

The purpose of this study was to understand the function of rfaF gene in Helicobacter pylori antibiotic resistance.

METHODS

The gene homologous recombination method was used for knockout and complementation of H. pylori rfaF gene. Various constructed strains were analysed for drug sensitivity to amoxicillin (AMO), tetracycline (TET), clarithromycin (CLA), metronidazole (MET), levofloxacin (LEV), and chloramphenicol (CHL) by agar plate dilution method. Drug sensitivity was further confirmed using a growth inhibition curve. Ethidium bromide (EB) accumulation experiments were performed to assess cell membrane permeability. PCR and sequence analysis were used to detect the rfaF gene.

RESULTS

The minimum inhibitory concentrations (MIC) of TET, CHL, AMO, and CLA in 11,637 rfaF knockout strain (ΔrfaF strain) were 4, 4, 2, and 2 times higher than those in 11,637 wild type (WT) strain, respectively. A multidrug-resistant (MDR) ΔrfaF strain also displayed the same trend; however, the degrees of increase were relatively small. Growth inhibition experiments indicated that the growth of the 11,637 ΔrfaF strain was higher with antibiotics at the MIC of the 11,637 WT strain than that of 11,637 rfaF-complemented strain (ΔrfaF/rfaF strain), whereas the 11,637 WT strain did not exhibit any growth. The 11,637 ΔrfaF strain was significantly reduced compared with the cumulative EB fluorescence intensity of the 11,637 WT and of 11,637ΔrfaF/rfaF strain, and the same trend appeared in the MDR strain. Among the 10 clinical strains, 9 clinical strains were found to have mutations in the conserved sequence of rfaF amino acids.

CONCLUSION

We found a new drug resistance gene, rfaF, in H. pylori, which changes the permeability of cell membrane to confer cross-resistance to AMO, TET, CLA, and CHL and is involved in clinical strain drug resistance. It can be used as a drug target.

Vitamin B6 is required for full motility and virulence in Helicobacter pylori

Despite recent advances in our understanding of how Helicobacter pylori causes disease, the factors that allow this pathogen to persist in the stomach have not yet been fully characterized. To identify new virulence factors in H. pylori, we generated low-infectivity variants of a mouse-colonizing H. pylori strain using the classical technique of in vitro attenuation. The resulting variants and their highly infectious progenitor bacteria were then analyzed by global gene expression profiling. The gene expression levels of five open reading frames (ORFs) were significantly reduced in low-infectivity variants, with the most significant changes observed for ORFs HP1583 and HP1582. These ORFs were annotated as encoding homologs of the Escherichia coli vitamin B₆ biosynthesis enzymes PdxA and PdxJ. Functional complementation studies with E. coli confirmed H. pylori PdxA and PdxJ to be bona fide homologs of vitamin B₆ biosynthesis enzymes. Importantly, H. pylori PdxA was required for optimal growth in vitro and was shown to be essential for chronic colonization in mice. In addition to having a well-known metabolic role, vitamin B₆ is necessary for the synthesis of glycosylated flagella and for flagellum-based motility in H. pylori. Thus, for the first time, we identify vitamin B₆ biosynthesis enzymes as novel virulence factors in bacteria. Interestingly, pdxA and pdxJ orthologs are present in a number of human pathogens, but not in mammalian cells. We therefore propose that PdxA/J enzymes may represent ideal candidates for therapeutic targets against bacterial pathogens.

Approximately half of the world’s population is infected with H. pylori, yet how H. pylori bacteria establish chronic infections in human hosts remains elusive. From gene array studies, we identified two genes as representing potentially novel colonization factors for H. pylori. These genes encoded enzymes involved in the synthesis of vitamin B₆, an important molecule for many metabolic reactions in living organisms. Little is currently known regarding vitamin B₆ biosynthesis in human pathogens. We showed that mutant H. pylori bacteria lacking an enzyme involved in de novo vitamin B₆ biosynthesis, PdxA, were unable to synthesize motility appendages (flagella) and were unable to establish chronic colonization in mice. Thus, this work identifies vitamin B₆ biosynthesis enzymes as novel virulence factors for bacterial pathogens. Interestingly, a number of human pathogens, but not their mammalian hosts, possess these genes, which suggests that Pdx enzymes may represent ideal candidates for new therapeutic targets.

Helicobacter pylori eradication therapy

Helicobacter pylori infection is the main cause of gastritis, gastroduodenal ulcers and gastric cancer. H. pylori eradication has been shown to have a prophylactic effect against gastric cancer. According to several international guidelines, the first-line therapy for treating H. pylori infection consists of a proton pump inhibitor (PPI) or ranitidine bismuth citrate, with any two antibiotics among amoxicillin, clarithromycin and metronidazole, given for 7-14 days. However, even with these recommended regimens, H. pylori eradication failure is still seen in more than 20% of patients. The failure rate for first-line therapy may be higher in actual clinical practice, owing to the indiscriminate use of antibiotics. The recommended second-line therapy is a quadruple regimen composed of tetracycline, metronidazole, a bismuth salt and a PPI. The combination of PPI-amoxicillin-levofloxacin is a good option as second-line therapy. In the case of failure of second-line therapy, the patients should be evaluated using a case-by-case approach. European guidelines recommend culture before the selection of a third-line treatment based on the microbial antibiotic sensitivity. H. pylori isolates after two eradication failures are often resistant to both metronidazole and clarithromycin. The alternative candidates for third-line therapy are quinolones, tetracycline, rifabutin and furazolidone; high-dose PPI/amoxicillin therapy might also be promising.

HELICOBACTER PYLORI INFECTION AND TREATMENT OUTCOME IN AN URBAN AUSTRALIAN POPULATION

BACKGROUND

To examine the rate of Helicobacter pylori infection in a group of symptomatic patients using rapid urease test and antral histology and report on their treatment outcomes.

METHODS

From a single-surgeon series in a tertiary teaching hospital, 200 consecutive symptomatic patients undergoing their first diagnostic upper gastrointestinal endoscopy during 2003-2004 were included in this retrospective audit. Campylobacter-like organism (CLO) test results were compared with the results of conventional histological examination plus Giemsa staining. Eradication rates and demographic data were collected.

RESULTS

One hundred and seventy-nine of 200 (89.5%) patients had antral biopsies for histology and for CLOtest. The CLOtest was positive in 31% (56/179) of patients. Thirty-two of 56 (57%) patients had an early-positive CLOtest (<24 h). The remaining 43% (24/56) of patients had a late-positive CLOtest (>24 h). Histological examination of the antral biopsy showed evidence of H. pylori in 28/56 (50%) patients with a positive CLOtest. H. pylori eradication therapy was prescribed in 51/56 (91%) patients with a positive CLOtest. Forty-five of 51 (88%) of these patients had a subsequent urea breath test. Urea breath test was positive in 17/45 (29%) patients after H. pylori eradication therapy was prescribed.

CONCLUSION

Rate of H. pylori in this series of symptomatic patients was 31%. As nearly half of the CLOtests became positive after 24 h, we suggest that the CLOtest should be re-examined 24 h after gastroscopy. Standard antral histology and CLOtest were in agreement in only 50% of cases, suggesting that the CLOtest is a more sensitive test. The failure rate of 29% for initial H. pylori eradication therapy reinforces the need for follow up after treatment.

One-year follow-up study of Helicobacter pylori eradication rate with 13C-urea breath test after 3-d and 7-d rabeprazole-based triple therapy

AIM: To investigate the long-term role of a 3-d rabeprazole-based triple therapy in patients with Helicobacter pylori(H pylori)-infected active peptic ulcers.

METHODS: We prospectively studied 115 consecutive patients with H pylori-infected active peptic ulcers. H pylori infection was confirmed if any two of H pylori DNA, histology, and rapid urease test were positive. Patients were assigned to either an open-labeled 3-d course of oral amoxicillin 1000 mg b.i.d., clarithromycin 500 mg b.i.d., and rabeprazole 20 mg b.i.d., or 7-d course of oral amoxicillin 1000 mg b.i.d., clarithromycin 500 mg b.i.d., and rabeprazole 20 mg b.i.d. Subsequently, all patients received oral rabeprazole 20 mg once daily until the 8^th wk. Three months after therapy, all patients were followed-up endoscopically for the peptic ulcer, H pylori DNA, histology, and rapid urease test. One year after therapy, H pylori infection was tested using the ¹³C-urea breath test.

RESULTS: The ulcer healing rates 3 mo after therapy were 81.0% vs 75.4% for the 3-d and 7-d groups [intention-to-treat (ITT) analysis, P = 0.47] respectively, and 90.4% vs 89.6% for the 3-d and 7-d groups [per-protocol (PP) analysis, P = 0.89] respectively. The eradication rates 3 mo after therapy were 75.9% vs 73.7% for the 3-d and 7-d groups (ITT, P = 0.79) respectively, and 84.6% vs 87.5% for the 3-d and 7-d groups (PP, P = 0.68) respectively. One year after therapy, seventy-five patients returned to receive the ¹³C-urea breath test, and the eradication rates were 78.4% vs 81.6% in 3-d and 7-d groups (PP, P = 0.73) respectively.

CONCLUSION: Our study showed the eradication rates against H pylori infection 3 and 12 mo after triple therapy were not different between the 3-d and 7-d rabeprazole-based groups. Therefore, the 3-d rabeprazole-based triple therapy may be an alternative treatment for peptic ulcers with H pylori infection.

N-acetylcysteine, a novel treatment for Helicobacter pylori infection

N-Acetylcysteine (NAC), being both a mucolytic agent and a thiol-containing antioxidant, may affect the establishment and maintenance of H. pylori infection within the gastric mucus layer and mucosa. Agar and broth dilution susceptibility tests determined the MIC of H. pylori strain SSI to NAC. H. pylori load in SSI strain-infected C57BL mice was determined as colony forming units per gram of gastric tissue. Gastritis assessment was scored and gastric surface hydrophobicity was determined by contact angle measurement. MICs of NAC were 5 to 10 and 10 to 15 mg/ml using the agar dilution and broth dilution methods, respectively. NAC (120 mg per day for 14 days) reduced the H. pylori load in mice by almost 1 log compared with sham treatment. Pretreatment with NAC (40 mg/day) also significantly reduced the H. pylori load but did not prevent H. pylori colonization. Both H. pylori infection and NAC reduced the surface hydrophobicity of murine gastric mucosa. No significant differences were observed in the gastritis scores of H. felis- or H. pylori-infected mice receiving either NAC or sham treatments. This study demonstrates that NAC inhibits the growth of H. pylori in both agar and broth susceptibility tests and in H. pylori-infected mice. NAC did not alter the severity of H. pylori- or H. felis-induced gastritis.

Helicobacter pylori: antibiotic resistance and eradication rates in Suffolk, UK, 1991-2001

Helicobacter pylori infection causes a number of gastrointestinal diseases and its current treatment is based on multidrug regimes including acid suppression and antimicrobials. The success of these regimes is determined by a number of factors including antibiotic resistance, which varies widely but is an increasing problem. Local data are important in establishing the most cost-effective eradication regime. Data have been collected prospectively on antibiotic resistance at Ipswich Hospital (Suffolk, UK) in all consecutive isolates of H. pylori from 1991 to 2001. The success of regimes consisting of a proton pump inhibitor, amoxycillin and metronidazole (PPI/A/M) has also been evaluated in patients found positive on serological testing in primary care using urea breath testing. Overall, metronidazole resistance was found in 31.7 % of isolates and clarithromycin resistance in 5.3 %. A significant increase in metronidazole resistance from 29.1 to 37.0 % (P = 0.022) and a decrease in clarithromycin resistance from 10.3 to 3.8 % (P = 0.014) was seen over the study period. Metronidazole resistance was significantly more common in women (P < 0.001) and young patients (P < 0.001). Eradication with PPI/A/M was successful in 89.9 % of patients and did not change significantly over the study period. Eradication rates were lower in young patients (P < 0.001). Whilst metronidazole resistance is increasing in Suffolk, this does not seem to have a significant effect on eradication rates. Metronidazole-based regimes are still effective first-line treatments in most patients.

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.

Effect of lactoferrin on Helicobacter felis induced gastritis

Lactoferrin possesses antibiotic, antiinflammatory, and immune-modulating properties that may be active against the gastritis-, ulcer- and cancer-inducing bacterium Helicobacter pylori. In vitro testing of bovine and human lactoferrin by several laboratories has shown significant bacteriostatic and bactericidal activity. Subsequent in vivo testing of bovine lactoferrin in animal models of H. pylori infection has shown beneficial effects of this agent. Our laboratory has utilized a mouse model that is infected with the feline strain of this bacterium, H. felis. The resulting gastritis that develops in this model and the effects of bovine lactoferrin and recombinant human lactoferrin (from Aspergillus niger var. awamori, Agennix Inc., Houston, Tex.) treatment were assessed by various measures. Infected animals treated with orally administered lactoferrin showed reversals in all parameters. In addition, when recombinant human lactoferrin was used in combination with low doses of amoxicillin or tetracycline, there was an enhancement in gastritis-reducing activity. Possible mechanisms for these effects of lactoferrin are discussed. Lactoferrin has significant, orally active in vivo actions and should be further investigated for clinical situations involving Helicobacter infections where it may have utility when administered alone and also when given in combination with established antibiotic agents.

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.