Cost-effectiveness of a tailored Helicobacter pylori eradication strategy based on the presence of a 23S ribosomal RNA point mutation that causes clarithromycin resistance in Korean patients

Overcoming antibiotic-resistant Helicobacter pylori infection: Current challenges and emerging approaches

Recent studies have shown a noticeable increase in global Helicobacter pylori (H. pylori) resistance, with clarithromycin resistance surpassing 15% in various areas. However, inadequate epidemiological monitoring, especially in developing countries, and the absence of uniform testing methods lead to discrepancies between regions and a possible underestimation of resistance levels. The complexity of treating H. pylori is driven by its highly dynamic genome, which is prone to frequent mutations contributing to phenotypical resistance. The usual course of action in empirical treatment involves using a combination of various drugs simultaneously, leading to significant resistance selection pressure and potential side effects. The emergence of H. pylori strains resistant to multiple drugs is closely tied to failures in first-line treatment, highlighting the need to prevent further resistance by using optimal initial empirical therapy or regimens guided by antibiotic susceptibility testing, requiring a collection of mixed samples and multiple isolates for accurate assessment. The emergence of new treatments like potassium-competitive acid blockers offers a hopeful approach to decrease antimicrobial usage while still ensuring effectiveness in comparison to traditional therapies with proton pump inhibitors. Additionally, the use of probiotics is under investigation to identify specific strains and formulations that may mitigate therapy-associated adverse effects.

Bismuth-Based Quadruple Therapy as First-Line Treatment for Clarithromycin-Resistant Helicobacter pylori Infection: A Prospective Randomized Comparison of 7- and 14-Day Treatment Regimens

Background/Aims

: Bismuth-based quadruple therapy (BQT) is a treatment option for clarithromycin-resistant Helicobacter pylori (HP) infection. The aim of this study was to compare the efficacy of 7-day BQT with that of 14-day BQT as first-line treatment for clarithromycin-resistant HP infection.

Methods

: A total of 162 treatment-naïve patients with peptic ulcer disease and clarithromycin-resistant HP infection confirmed by real-time polymerase chain reaction (RT-PCR) were enrolled. The enrolled patients were prospectively randomized to receive BQT for either 7 or 14 days of treatment. Eradication of HP infection was assessed using a 13C-urea breath test. Eradication and adverse event rates of the two groups were assessed.

Results

: The overall eradication rates in the intention-to-treat (ITT) and per-protocol (PP) analyses were 83.0% (95% confidence interval [CI], 77.2% to 88.9%; 132/159) and 89.8% (95% CI, 84.9% to 94.7%; 132/147), respectively. The eradication rates in the ITT analysis were 79.0% (64/81) in the 7-day group and 87.2% (68/78) in the 14-day group (p=0.170). The eradication rates in the PP analysis were 86.5% (64/74) in the 7-day group and 93.2% (68/73) in the 14-day group (p=0.182). Clinically significant adverse events occurred in 18.2% of patients. There was no statistically significant difference in the rates of individual or all adverse events between the two groups.

Conclusions

: Both 7-day and 14-day BQT were effective and safe as first-line therapy for HP infections identified as resistant to clarithromycin by RT-PCR. For clarithromycin-resistant HP infections, 7-day BQT may be sufficient as first-line therapy.

The use of real-world evidence to generate cost analysis of antibiotic susceptibility testing (AST) in patients with Helicobacter pylori treatment failure in Thailand: A large population-based study

Background

H. pylori eradication is effective for gastric cancer prevention. Treatment failure is caused by increased antibiotic resistance. This study aimed to determine eradication rates and perform cost analysis between susceptibility-guided therapy and empirical treatment in patients with H. pylori treatment failure.

Methods

This retrospective cohort study included patients with dyspepsia undergoing gastroscopy at tertiary care center in Thailand from March 2014 to October 2021. Treatment failure was defined as persistent H. pylori infection after ≥1 regimen completion. Early AST was defined as AST performed shortly after first-line treatment failure. Demographic data, AST results, eradication regimens, and medication costs were collected from database and reviewed.

Results

Of 1080 patients with H. pylori infection, 315 had treatment failure (mean age 58.4 years; 44.4 % males). AST of 85 strains demonstrated resistance to levofloxacin (57.6 %), metronidazole (51.8 %), clarithromycin (44.7 %), and amoxicillin (4.7 %). In multivariate analysis, sequential therapy was significantly associated with treatment failure (OR 1.66; 95%CI 1.01-2.74, p = 0.045), whereas vonoprazan-containing therapy was related to treatment success (OR 1.60; 95%CI 1.04-2.48, p = 0.034). Medication nonadherence (OR 37.97; 95%CI 8.97-160.65, p < 0.001) contributed to treatment failure. Susceptibility-guided therapy provided better eradication rate than empirical therapy (97.5% vs. 65.5 %, OR 20.54; 95%CI 4.92-85.81, p < 0.001) in treatment failure group. Twenty-four patients had early AST, while 61 had AST after treatment failures. Most patients with early AST achieved treatment success by second-line eradication. Early AST provided significantly lower total average cost of treatment than group without AST ($368.2 vs. $402.0 per patient, p = 0.034) and AST after treatment failures ($368.2 vs. $752.8 per patient, p < 0.001). Early AST group had the lowest cost of subsequent medication, posttreatment urea breath test, and hospital visits.

Conclusion

Susceptibility-guided therapy provided significantly higher eradication rate than empirical therapy in patients with treatment failure. Early AST might be a cost-effective strategy for H. pylori eradication after failed therapy and can prevent unnecessary antibiotic use in Thailand.

Comparison of Amoxicillin Administered Twice versus Four Times a Day in First-Line Helicobacter pylori Eradication Using Tegoprazan, Clarithromycin, and Bismuth: A Propensity Score Matching Analysis

This study aimed to investigate the effects of different amoxicillin (AMX) dosing schedules on bismuth quadruple therapy in Helicobacter pylori treatment-naïve patients. A total of 139 H. pylori-infected patients received a 2-week eradication regimen consisting of 50 mg tegoprazan, 500 mg clarithromycin, and 300 mg bismuth tripotassium dicitrate twice daily, 1000 mg AMX twice daily (BID group), or 500 mg AMX four times daily (QID group). We performed a urea breath test to evaluate H. pylori eradication eight weeks after treatment and compared the H. pylori eradication rate, patient compliance, and adverse drug events between the BID and QID groups. Based on propensity score matching, 114 and 100 patients were included in intention-to-treat (ITT) and per-protocol (PP) analyses, respectively. The H. pylori eradication rate did not differ significantly according to the ITT (82.5% vs. 87.7%, p = 0.429) and PP (95.9% vs. 98.0%, p = 0.536) analyses between the BID and QID groups. No significant differences were found in treatment compliance or adverse drug event rates between the two groups. In conclusion, the eradication rate of first-line H. pylori therapy containing tegoprazan, clarithromycin, and bismuth was not affected by AMX dosing schedules administered twice and four times daily.

Bismuth add-on improves the efficacy of 2-week tegoprazan-based triple therapy for first-line Helicobacter pylori eradication: a real-world evidence study

BACKGROUND

This study aimed to investigate the efficacy of bismuth added to a 2-week triple therapy consisting of tegoprazan (TPZ), amoxicillin, and clarithromycin for first-line Helicobacter pylori eradication.

RESEARCH DESIGN AND METHODS

We reviewed the retrospective data of patients who received a 2-week TPZ-based triple therapy with or without 300 mg bismuth twice daily. The primary endpoint was the H. pylori eradication rate of adding bismuth to the TPZ-based triple regimen (TAC-B group), compared to no bismuth added (TAC group).

RESULTS

In total, 306 and 256 patients were included in the intention-to-treat (ITT) and per-protocol (PP) analyses, respectively. The eradication success rates were significantly higher in the TAC-B group than in the TAC group (ITT, 82.9% vs. 71.8%, p = 0.029; PP, 95.8% vs. 87.5%, p = 0.027, respectively). The adherence rate to the eradication regimen was 100% in the TAC-B group and 97.0% in the TAC group. The adverse drug event rate in the TAC-B group was comparable to that in the TAC group (29.2% vs. 27.3%, p = 0.742). No use of bismuth was significantly associated with eradication failure (p = 0.038).

CONCLUSIONS

The bismuth add-on increased the first-line H. pylori eradication rate of 2-week TPZ-based triple therapy.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov identifier is NCT05453994.

Detection of Clarithromycin Resistance in Helicobacter pylori Using MmaxSure™ H. pylori &amp; ClaR Assay

INTRODUCTION

Clarithromycin resistance is a crucial factor in the eradication of Helicobacter pylori. This study aimed to evaluate the performance of MmaxSure™ H. pylori & ClaR Assay (MmaxSure™) in the diagnosis and detection of clarithromycin resistance in H. pylori.

METHODS

Subjects who underwent esophagogastroduodenoscopy between April 2020 and October 2022 were enrolled. The diagnostic performances of MmaxSure™ and dual priming oligonucleotide (DPO)-based multiplex polymerase chain reaction (PCR) were compared with the rapid urease test and culture. Secondary gene sequencing analysis was performed in discordant cases of PCR tests.

RESULTS

A total of 156 gastric biopsy samples were analyzed. In H. pylori detection, MmaxSure™ showed a 95.9% sensitivity (95% CI: 90.6-98.6), a 42.7% specificity (95% CI: 26.3-60.7), and a kappa value of 0.457. For the detection of A2143G mutation samples, MmaxSure™ showed a 91.2% sensitivity (95% CI: 76.3-98.1), a 93.4% specificity (95% CI: 87.5-97.1), and a kappa value of 0.804. There were a total of 10 discordant cases compared to gene sequencing in A2143G mutation detection for MmaxSure™.

CONCLUSION

In this study, MmaxSure™ showed comparable diagnostic performance to DPO-PCR in the detection of the H. pylori and A2143G mutation. Further research is needed to confirm the clinical effectiveness of the MmaxSure™ assay in H. pylori eradication.

Prospective Evaluation of a New Liquid-Type Rapid Urease Test Kit for Diagnosis of Helicobacter pylori

BACKGROUND/AIMS

Rapid and accurate diagnostic tools are essential for the timely recognition of Helicobacter pylori (H. pylori) in clinical practice. The rapid urease test (RUT) is a comparatively accurate and time-saving method recommended as a first-line diagnostic test. The primary objective of conducting the RUT is to obtain rapid results, thus enabling the initiation of an eradication therapy based on clarithromycin resistance testing. This study aimed to assess the reaction time and accuracy of a new liquid-type RUT.

METHOD

In this prospective study, consecutive dyspeptic or check-up patients referred to our clinic for endoscopy were assessed to evaluate the rapidity and accuracy of a novel liquid-type RUT (Helicotest®, WON Medical, Bucheon, Republic of Korea) compared with another commercial RUT kit (HP kit, Chong Kun Dang, Seoul, Republic of Korea) and a real-time quantitative PCR-based assay (Seeplex® H.pylori-ClaR Detection, Seegene, Republic of Korea). RUTs were analyzed at 10 min, 30 min, 60 min, and 120 min.

RESULTS

Among the 177 enrolled patients, 38.6% were infected with H. pylori. The positivity rates of the liquid-type RUT were 26.1, 35.8, 39.2%, and 41.5% at 10, 30, 60, and 120 min, respectively. When compared with the HP kit test, the time needed to confirm positivity was significantly reduced by 28.6 min (95% CI, 16.60-39.73, p < 0.0001). Helicotest® had a greater accuracy (96.02 ± 1.47), sensitivity (98.53 ± 1.46) and NPV (99.03 ± 0.97) compared to the HP kit.

CONCLUSIONS

Compared to the commonly used RUT, the new liquid-type RUT presented faster and reliable results. Such findings could improve H. pylori treatment outcomes, particularly in outpatient clinical settings.

Tailored therapy guided by genotypic resistance of clarithromycin and levofloxacin detected by polymerase chain reaction in the first-line treatment of Helicobacter pylori infection

OBJECTIVES

We aimed to explore the efficacy and safety of tailored therapy guided by genotypic resistance in the first-line treatment of Helicobacter pylori (H. pylori) infection in treatment-naive patients.

METHODS

Gastric mucosal specimens were taken during gastroscopy, and main mutations of clarithromycin- and levofloxacin-resistant genes were detected by polymerase chain reaction (PCR). Sensitive antibiotics were selected individually for treating H. pylori infection with tailored bismuth-containing quadruple therapy (BQT) consisting of esomeprazole 20 mg twice daily, bismuth potassium citrate 220 mg twice daily, amoxicillin 1 g twice daily, and clarithromycin 500 mg twice daily, or levofloxacin 500 mg once daily, or metronidazole 400 mg four times daily. Safety and patient compliance were assessed 1-3 days after eradication. Treatment outcome was evaluated by urea breath test 4-8 weeks after eradication.

RESULTS

One hundred and thirty-two treatment-naive patients with H. pylori infection were included. PCR results suggested resistance rates of 47.7% and 34.9% for clarithromycin and levofloxacin, respectively, and a dual resistance rate of 18.2%. Eradication rates of tailored BQT were 87.1% and 95.8% by intention-to-treat (ITT) analysis and per-protocol (PP) analysis, respectively. There was no statistically significant difference in the efficacy of 7-day clarithromycin-containing, 7-day levofloxacin-containing, and 14-day full-dose metronidazole-containing BQT (ITT analysis: P = 0.488; PP analysis: P = 0.833). The incidence of adverse events was 19.7%, and patient compliance was 97.7%.

CONCLUSION

Tailored BQT guided by genotypic resistance can achieve satisfactory efficacy, safety, and patient compliance in the first-line treatment of H. pylori infection.

Efficacy of genotypic susceptibility-guided tailored therapy for Helicobacter pylori infection: A systematic review and single arm meta-analysis

BACKGROUND AND AIM

The prevalence of antibiotic resistance for Helicobacter pylori (H. pylori) has been increasing over the year, making it more difficult for traditional empirical therapy to successfully eradicate H. pylori. Thus, tailored therapy (TT) guided by molecular-based antibiotic susceptibility testing (AST) has been frequently recommended. We conducted a single-arm meta-analysis to determine the efficacy of tailored therapy guided by molecular-based AST.

METHODS

A systematic literature review was performed on multiple databases, and studies on molecular-based TT were included. The eradication rates of TT by intention-to-treat (ITT) and per-protocol (PP) analyses were pooled respectively.

RESULTS

A total of 35 studies from 31 literature (4626 patients) were included in the single-arm meta-analysis. Overall, the pooled eradication rate of TT was 86.9% (95% CI:84.7%-89.1%) by the ITT analysis, and 91.5% (95% CI:89.8%-93.2%) by PP analysis. The pooled eradication rates of first-line TT and rescue TT were 86.6% and 85.1% by ITT analysis and 92.0% and 87.9% by PP analysis, respectively. When tailored rescue therapy was based on the genotypic resistance to at least four antibiotics, the pooled eradication rates reached 89.4% by ITT analysis and 92.1% by PP analysis. For genotype-susceptive strains, the pooled eradication rate of TT with targeted antibiotics was 93.1% (95% CI:91.3%-94.9%), among which the pooled eradication rate of tailored bismuth quadruple therapy was the highest (94.3%). Besides, the eradication rate of 7-day TT or tailored triple therapy without bismuth for genotype-susceptive strains could both reach more than 93.0%.

CONCLUSION

Tailored therapy guided by molecular-based AST can achieve somewhat ideal therapeutic outcomes. TT with a 7-day duration or without bismuth for genotype-susceptible strains can achieve good eradication efficacy. The effectiveness of TT can be improved to some extent by expanding the coverage of AST or by adding bismuth.

Optimizing Helicobacter pylori Treatment: An Updated Review of Empirical and Susceptibility Test-Based Treatments

As the rate of discovery of drug-resistant Helicobacter pylori cases increases worldwide, the relevant societies have updated their guidelines for primary eradication regimens. A promising strategy against drug-resistant H. pylori is tailored therapy based on the results of an antibiotic susceptibility test; however, it is difficult to apply this strategy to all cases. Although culture-based antibiotic susceptibility tests can assess resistance to any antimicrobial agent, their greatest disadvantage is the time required to draw a conclusion. In contrast, molecular-based methods, such as polymerase chain reaction, can rapidly determine the presence of resistance, although a single test can only test for one type of antimicrobial agent. Additionally, the limited availability of facilities for molecular-based methods has hindered their widespread use. Therefore, low-cost, minimally invasive, simple, and effective primary regimens are needed. Several studies have compared the efficacy of the latest primary eradication regimens against that of tailored therapies, and their results have shaped guidelines. This article reviews the latest research on empirical and tailored treatments for H. pylori infections. Evidence for the superiority of tailored therapy over empirical therapy is still limited and varies by region and treatment regimen. A network meta-analysis comparing different empirical treatment regimens showed that vonoprazan triple therapy provides a superior eradication effect. Recently, favorable results towards vonoprazan dual therapy have been reported, as it reached eradication levels similar to those of vonoprazan triple therapy. Both vonoprazan dual therapy and tailored therapy based on antibiotic susceptibility tests could contribute to future treatment strategies.

Effective Eradication Regimen and Duration According to the Clarithromycin Susceptibility of Helicobacter pylori Determined Using Dual Priming Oligonucleotide-Based Multiplex Polymerase Chain Reaction

Background/Aims

Dual priming oligonucleotide-based multiplex polymerase chain reaction (DPO-PCR) has recently been used for both the detection of Helicobacter pylori and the identification of H. pylori 23S ribosomal RNA point mutations that cause clarithromycin resistance. The aim of this study was to investigate the duration of effective standard triple therapy in a clarithromycin susceptible group and of bismuth-based quadruple therapy in a resistant group based on DPO-PCR.

Methods

We retrospectively analyzed the electronic medical records of 184 patients who, between September 2019 and December 2020, received eradication therapy following detection of H. pylori, and the subsequent identification of the clarithromycin susceptibility of their H. pylori using DPO-PCR. Patients were treated with 7- or 14-day standard triple therapy in the clarithromycin susceptible group, whereas 7- or 14-day bismuth-based quadruple therapy in the clarithromycin resistance group.

Results

In the clarithromycin susceptible group, per-protocol analyses showed eradication rates of 87.5% (42/48; 95% confidence interval [CI], 77.1% to 95.8%) for 7-day therapy and 87.2% (41/47; 95% CI, 78.7% to 95.7%) for 14-day therapy (p=0.969). The eradication rates in the clarithromycin resistance group were 91.4% (32/35; 95% CI, 80.0% to 100.0%) for 7-day therapy and 90.3% (28/31; 95% CI, 77.4% to 100.0%) for 14-day therapy (p=0.876). There was no significant difference in the eradication rates, patient compliance, or rate of adverse events between the 7- and 14-day therapies for both groups.

Conclusions

Compared to the 14-day therapy, 7-day eradication therapy is sufficient after DPO-PCR-based clarithromycin susceptibility testing.

Antibiotic Resistance, Susceptibility Testing and Stewardship in Helicobacter pylori Infection

Despite the declining trend of Helicobacter pylori (H. pylori) prevalence around the globe, ongoing efforts are still needed to optimize current and future regimens in view of the increasing antibiotic resistance. The resistance of H. pylori to different antibiotics is caused by different molecular mechanisms, and advancements in sequencing technology have come a far way in broadening our understanding and in facilitating the testing of antibiotic susceptibility to H. pylori. In this literature review, we give an overview of the molecular mechanisms behind resistance, as well as discuss and compare different antibiotic susceptibility tests based on the latest research. We also discuss the principles of antibiotic stewardship and compare the performance of empirical therapies based on up-to-date resistance patterns and susceptibility-guided therapies in providing effective H. pylori treatment. Studies and clinical guidelines should ensure that the treatment being tested or recommended can reliably achieve a pre-agreed acceptable level of eradication rate and take into account the variations in antibiotic resistance across populations. Local, regional and international organizations must work together to establish routine antibiotic susceptibility surveillance programs and enforce antibiotic stewardship in the treatment of H. pylori, so that it can be managed in a sustainable and efficient manner.

Quantitative multiplex real-time polymerase chain reaction assay for the detection of Helicobacter pylori and clarithromycin resistance

BACKGROUND

Identifying clarithromycin resistance is essential for eradicating Helicobacter pylori (HP). Therefore, we evaluated the performance of Allplex™ H.pylori & ClariR Assay (Allplex™) for diagnosing and detecting clarithromycin resistance in HP.

METHODS

Subjects who underwent esophagogastroduodenoscopy between April 2020 and August 2021 at Incheon St. Mary's hospital were enrolled in this study. The diagnostic performances of Allplex™ and dual priming oligonucleotide (DPO)-based multiplex polymerase chain reaction (PCR) were compared with sequencing as the gold standard.

RESULTS

A total of 142 gastric biopsy samples were analyzed. Gene sequencing revealed 124 HP infections, 42 A2143G mutations, 2 A2142G mutations, one dual mutation, and no A2142C mutation. DPO-PCR showed 96.0% sensitivity and 100.0% specificity for HP detection; the corresponding rates for Allplex™ were 99.2% and 100.0%. DPO-PCR showed 88.3% sensitivity and 82.0% specificity for A2143G mutation, and Allplex™ showed 97.6% and 96.0%. The Cohen's Kappa coefficient for overall test results was 0.56 for DPO-PCR and 0.95 for Allplex™.

CONCLUSION

Allplex™ showed comparable diagnostic performance with direct gene sequencing and non-inferior diagnostic performance to DPO-PCR. Further research is required to confirm whether Allplex™ is an effective diagnostic tool for the eradication of HP.

Helicobacter pylori Infection: Antibiotic Resistance and Solutions for Effective Management in Africa

Helicobacter pylori (H. pylori) infection is ubiquitous worldwide, with prevalence rates of greater than 70% in Africa. Symptomatic patients present with foregut gastrointestinal symptoms which can be readily diagnosed with standardized non-invasive or invasive tests. The biggest challenge, however, is in the management of this condition with rising antimicrobial resistance rates to most of the antibiotics recommended for therapy. This is a problem worldwide, but more specifically in Africa, where the socio-economic and political climate is such that eradication of this organism seems impossible. Furthermore, the recommended antimicrobial susceptibility testing for drug resistance is not widely available in Africa due to the lack of infrastructural as well as human resources. With the widespread unregulated use of antibiotics in some parts of Africa, the figures of antimicrobial resistance are likely to soar. In the face of these significant challenges, this 'perspectives' article aims to address the issue of antimicrobial resistance in Africa, by providing achievable and targeted goals to curb the spread of infection and rising antimicrobial resistance.

Effectiveness of 7-day triple therapy with half-dose clarithromycin for the eradication of Helicobacter pylori without the A2143G and A2142G point mutations of the 23S rRNA gene in a high clarithromycin resistance area

BACKGROUND

Tailored therapy has been widely used for patients with Helicobacter pylori (H. pylori) infection in South Korea. Herein, we evaluated the treatment outcomes of tailored clarithromycin-based triple therapy (TT) in patients infected with H. pylori.

METHODS

We enrolled 460 patients without A2142G and A2143G point mutations by dual priming oligonucleotide-based polymerase chain reaction who had taken TT and undergone the urease breath test to evaluate eradication in clinical practice. Eradication rates according to the treatment duration and dose of clarithromycin were analyzed.

RESULTS

Among 460 patients (164 women, median age 63.0 years), 250 patients underwent TT with full-dose clarithromycin (TT-full CLA), and 216 patients underwent TT with half-dose clarithromycin (TT-half CLA). The eradication rates were 88.0% (220/250) in patients with TT-full CLA and 85.2% (179/210) in patients with TT-half CLA. In 250 patients with TT-full CLA, the eradication rates were 86.8% (33/38) in patients with 7-day TT-full CLA and 88.2% (187/212) in patients with 10-day or 14-day TT-full CLA (P = 0.788). In 210 patients with TT-half CLA, the eradication rates were 84.2% (139/165) in those with a 7-day TT-half CLA and 88.9% (40/45) in those with a 10-day or 14-day TT-half CLA (P = 0.436).

CONCLUSION

For patients with H. pylori infection without A2142G and A2143G point mutations by DPO-PCR in clinical practice, treatment extension above 7-day TT with full CLA did not improve the eradication rates. Future studies on the treatment outcomes of TT-half CLA considering effectiveness and compliance are warranted.

Current role of tailored therapy in treating Helicobacter pylori infections. A systematic review, meta-analysis and critical analysis

BACKGROUND AND AIMS

Recent guidelines dictate that all Helicobacter pylori (H. pylori) infected subjects should receive curative therapy. The efficacy of empirical regimens for H. pylori eradication might decline with bacterial, drug, and host factors. The necessity of a tailored therapy still remains controversial. Here we provide a meta-analysis of the current status of susceptibility-based (tailored) therapy in which susceptibility-based therapies were compared to the currently accepted choice of empiric therapy. In this rapidly closing era, neither the susceptibility nor empiric therapies were routinely optimized, such that we report the outcome of comparisons on the efficacy of unoptimized tailored vs. locally preferred empiric treatments.

METHODS

PubMed, Medline, and Embase databases were searched using suitable keywords. Individual and pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using the fixed- or random-effects model as appropriate. Heterogeneity was calculated employing the Cochrane Q test and I² values, whereas the possibility of publication bias was examined by constructing funnel plots. Additionally, subgroup and sensitivity analyses were performed.

RESULTS

Thirty-four studies were included with a total of 9613 patients. Tailored therapy proved superior to empiric treatment [OR 2.07 (95% CI 1.53-2.79)]. However, tailored therapy achieved eradication rates >90% in only 15 (44%) studies and >95% in only 6 (17.6%).

CONCLUSIONS

Although tailored therapy performed better than empiric treatment, the lack of optimization of therapies failed to reliably achieve high cure rates (>90%). These results emphasize that H. pylori infection, like other infectious diseases, should utilize the principles of antimicrobial stewardship in relation to treatment guidance.

Seven Days of Bismuth-Based Quadruple Therapy Is as Effective for the First-Line Treatment of Clarithromycin-Resistant Confirmed Helicobacter pylori Infection as 14 Days of Bismuth-Based Quadruple Therapy

Background/Aims: Point mutations in the 23S ribosomal RNA gene have been associated with Helicobacter pylori (H. pylori) clarithromycin resistance and bismuth-based quadruple therapy (BQT) is one of the options for the treatment of clarithromycin-resistant H. pylori. Current H. pylori treatment guidelines recommend BQT for 10–14 days. This study aims to compare the eradication extents according to 7-day and 14-day BQT treatment for treatment-naïve clarithromycin-resistant confirmed H. pylori infection. Methods: We retrospectively investigated treatment-naïve H. pylori infection cases from March 2019 to December 2020, where patients were treated with BQT. Clarithromycin resistance was identified with a dual-priming oligonucleotide-based multiplex polymerase chain reaction method. We reviewed a total of 126 cases. Fifty-three subjects were treated with a 7-day BQT regimen (7-day group), and 73 subjects were treated with a 14-day BQT regimen (14-day group). We evaluated the total eradication extent of the BQT and compared the eradication extents of the two study groups. Results: Total eradication extent of H. pylori was 83.3% (105/126). The eradication extents of the two groups were as follows: 7-day group (81.1% (43/53)), 14-day group (84.9% (62/73), p = 0.572) by intention-to-treat analysis; 7-day group (95.6% (43/45)), 14-day group (92.5% (62/67), p = 0.518) by per-protocol analysis. The moderate or severe adverse event extents during the eradication were 30.2% (16/53) in the 7-day group and 19.2% (14/73) in the 14-day group (p = 0.152). Conclusions: The 7-day BQT regimen was as effective as the 14-day BQT regimen in the eradication of treatment-naïve clarithromycin-resistant H. pylori infection.

Management of Helicobacter pylori Infection: A Comparison between Korea and the United States

Helicobacter pylori has been well known to cause gastritis, peptic ulcers, mucosa-associated lymphoid tissue, and gastric cancer. The importance of H. pylori eradication has been emphasized; however, the management of H. pylori infection is difficult in clinical practice. In both Eastern and Western countries, there has been a constant interest in confirming individuals who should be tested and treated for H. pylori infection and developing methods to diagnose H. pylori infection. Many studies have been implemented to successfully eradicate H. pylori, and various combinations of eradication regimens for H. pylori infection have been suggested worldwide. Based on the findings of previous studies, a few countries have published their own guidelines that are appropriate for their country; however, these country-specific guidelines may differ depending on the circumstances in each country. Evidence-based guidelines and clinical practice updates for the treatment of H. pylori infection have been published in Korea and the United States in 2021. This review will summarize the similarities and differences in the management of H. pylori infection in Korea and the United States, focusing on indications, diagnosis, and treatments based on recent guidelines and recommendations in both countries.

Susceptibility testing alone will not reliably achieve high Helicobacter pylori cure rates: A systematic review and meta-analysis

BACKGROUND AND AIM

Not all the susceptibility-guided therapies for Helicobacter pylori (H. pylori) infection achieve excellent eradication rates. The aim of this study was to perform a systematic review and meta-analysis to identify the optimal regimen for H. pylori treatment based on antibiotic susceptibility.

METHODS

A systematic search was performed in multiple databases. Studies reporting eradication rates of H. pylori with susceptibility-guided therapies were selected. Meta-analysis was conducted to calculate the pooled eradication rate among the treatment regimens.

RESULTS

Forty-eight eligible studies with 101 susceptibility-guided treatment arms were included. The overall eradication rate in patients harboring susceptible strains was 95.0% (95% CI, 94.1-95.9%), but only 63.4% of treatment arms (64/101) achieved good eradication rates (≥ 90%). Pooled eradication rates in patients with susceptible strains were: 93.4% (95% CI, 92.0-94.8%) for clarithromycin, 99.0% (95% CI, 98.1-100%) for nitroimidazoles and 95.4% (95% CI, 93.6-97.2%) for fluoroquinolones. Among the arms using a triple therapy, 66.7% (28/42) using clarithromycin, 84.2% (16/19) using nitroimidazoles and 70.8% (17/24) using fluoroquinolones achieved good (≥ 90%) eradication rates. Of 13 arms using sequential therapy, ≥ 90% eradication was achieved in 14.3% (1/7) using clarithromycin, 25.0% (1/4) using nitroimidazoles and both arms (2/2) using fluoroquinolones.

CONCLUSIONS

Susceptibility testing alone seemed insufficient to reliably attain high H. pylori cure rates. The eradication rate in patients with nitroimidazoles susceptible strains was higher than those of fluoroquinolones and clarithromycin.

Antibiotic resistance of Helicobacter pylori isolated from children in Chongqing, China

The resistance of Helicobacter pylori (H. pylori) to antibiotics has been increasing worldwide and varies across different geographic areas and times. Limited studies reported the prevalence of antibiotic resistance and its related gene mutations in children in Chongqing, a city located in southwest China. We collected 112 H. pylori strains isolated from gastric biopsies of 156 children at Children's Hospital of Chongqing Medical University and calculated resistance rates of these strains to six antibiotics. The A2143G and A2142G mutations in 23S rRNA gene, which are related to clarithromycin resistance, and Asn87 and Asp91 mutations in gyrA gene, which are related to levofloxacin resistance, were investigated in 102 strains. The resistance rates to clarithromycin, metronidazole, and levofloxacin were 47.3% (53/112), 88.4% (99/112), and 18.8% (21/112), respectively. No resistance to amoxicillin, tetracycline, and furazolidone was observed. Dual and triple resistance percentages were 37.5% (42/112) and 10.7% (12/112), respectively. The detection rate of A2143G mutation in 23S rRNA gene was 83.3% (40/48). The detection rates of mutations of Asn87 and Asp91 in gyrA gene were 52.6% (10/19) and 36.8% (7/19), respectively. Conclusion: The prevalence of H. pylori resistance to clarithromycin, metronidazole, and levofloxacin was high in children in Chongqing, China. The A2143G mutation was detected in most clarithromycin-resistant strains, and Asn87 and Asp91 of gyrA mutation points were common in levofloxacin-resistant strains. In clinical practice, anti-H. pylori therapy should be individualized based on a susceptibility test.  What is Known: • The resistance of H. pylori to antibiotics changes with the geographic areas and that in Asia the resistance rate is high. • Mutation plays a vital role in antibiotics resistance of H. pylori. What is New: • High resistance rates to single and multiple antibiotics in children of Chongqing, a city located in southwest China, were observed. • Molecular assays showed good conformance with susceptibility test results to direct antibiotic resistance of H. pylori.

Empirical vs. Susceptibility-Guided Treatment of Helicobacter pylori Infection: A Systematic Review and Meta-Analysis

Background

Treating Helicobacter pylori infection according to antibiotic resistance has been frequently recommended. However, information on its real effectiveness is scarce.

Aim

The aim of this study is to perform a meta-analysis comparing empirical vs. susceptibility-guided treatment of H. pylori.

Methods

Selection of studies: Studies comparing empirical versus susceptibility-guided treatment were selected. Search strategy: electronic and manual up to August 2021. Data synthesis: by intention-to-treat (random-effects model).

Results

Overall, 54 studies were included (6,705 patients in the susceptibility-guided group and 7,895 in the empirical group). H. pylori eradication rate was 86 vs. 76%, respectively (RR: 1.12; 95% CI: 1.08-1.17; I 2: 83%). Similar results were found when only RCTs were evaluated (24 studies; RR: 1.16; 95% CI: 1.11-1.22; I 2: 71%) and when susceptibility testing was assessed by culture (RR: 1.12; 95% CI: 1.06-1.18) or PCR (RR: 1.14; 95% CI: 1.05-1.23). For first-line treatments (naïve patients; 30 studies), better efficacy results were obtained with the susceptibility-guided strategy (RR: 1.15; 95% CI: 1.11-1.20; I 2: 79%). However, for empirical first-line quadruple regimens, in particular (both with and without bismuth, excluding the suboptimal triple therapies), not based on CYP2C19 gene polymorphism, no differences in efficacy were found compared with the susceptibility-guided group (RR: 1.04; 95% CI: 0.99-1.09); this lack of difference was confirmed in RCTs (RR: 1.05; 95% CI: 0.99-1.12). For rescue therapies (13 studies, most 2nd-line), similar results were demonstrated for both strategies, including all studies (RR: 1.09; 95% CI: 0.97-1.22; I 2: 82%) and when only RCTs were considered (RR: 1.15; 95% CI: 0.97-1.36).

Conclusion

The benefit of susceptibility-guided treatment over empirical treatment of H. pylori infection could not be demonstrated, either in first-line (if the most updated quadruple regimens are prescribed) or in rescue therapies.

Cost-Effectiveness of Empirical Bismuth-Based Quadruple Therapy and Tailored Therapy After Clarithromycin Resistance Tests for Helicobacter pylori Eradication

BACKGROUND

The eradication rate of clarithromycin-based standard triple therapy (STT) for Helicobacter pylori infection has decreased due to clarithromycin resistance (CR). We evaluated the cost-effectiveness of tailored therapy according to CR test results, and compared the results of STT with those of empirical bismuth quadruple therapy (BQT).

METHODS

The prospectively collected data of 490 H. pylori-positive patients with chronic gastritis or peptic ulcer disease were retrospectively analyzed. Among them, 292 patients underwent CR testing using dual-priming oligonucleotide-based polymerase chain reaction. The tailored group (n = 292) consisted of patients treated with STT for 7 days and BQT for 10 days as per their CR test results. The remaining patients were assigned to the empirical group (n = 198) and received BQT for 10 days without a CR test. The eradication rate, adverse events and medical costs associated with H. pylori eradication therapy were investigated.

RESULTS

In the tested patients (tailored group), the CR-positive rate was 32.2% (n = 94/292). The eradication rate according to an intention-to-treat analysis was 87.7% in the tailored group and 91.8% in the empirical group (P = 0.124); the respective rates were 94.4% and 97.9% by per-protocol analysis (P = 0.010). The frequency of adverse events was lower in the empirical group than the tailored group (35.1% vs. 52.7%, P < 0.001). Total per capita medical costs were $406.50 and $503.50, respectively.

CONCLUSIONS

Ten-day empirical BQT was more effective, safer, and less expensive than tailored therapy based on a CR test for H. pylori eradication.

Bismuth-Based Quadruple Therapy versus Metronidazole-Intensified Triple Therapy as a First-Line Treatment for Clarithromycin-Resistant Helicobacter pylori Infection: A Multicenter Randomized Controlled Trial

Background/Aims

Clarithromycin resistance is a main factor for treatment failure in the context of Helicobacterpylori infection. However, the treatment regimen for clarithromycin-resistant H. pylori infection has not yet been determined. We aimed to compare the efficacy and cost-effectiveness of 14-day bismuth-based quadruple therapy versus 14-day metronidazole-intensified triple therapy for clarithromycin-resistant H. pylori infection with genotypic resistance.

Methods

This was a multicenter, randomized, controlled trial. A total of 782 patients with H. pylori infection examined using sequencing-based clarithromycin resistance point mutation tests were recruited between December 2018 and October 2020 in four institutions in Korea. Patients with significant point mutations (A2142G, A2142C, A2143G, A2143C, and A2144G) were randomly assigned to receive either 14-day bismuth-based quadruple therapy (n=102) or 14-day metronidazole-intensified triple therapy (n=99).

Results

The overall genotypic clarithromycin resistance rate was 25.7% according to the sequencing method. The eradication rate of 14-day bismuth-based quadruple therapy was not significantly different in the intention-to-treat analysis (80.4% vs 69.7%, p=0.079), but was significantly higher than that of 14-day metronidazole-intensified triple therapy in the per-protocol analysis (95.1% vs 76.4%, p=0.001). There were no significant differences in the incidence of side effects. In addition, the 14-day bismuth-based quadruple therapy was more cost-effective than the 14-day metronidazole-intensified triple therapy.

Conclusions

Fourteen-day bismuth-based quadruple therapy showed comparable efficacy with 14-day metronidazole-intensified triple therapy, and it was more cost-effective in the context of clarithromycin-resistant H. pylori infection.

Comparison of tailored Helicobacter pylori eradication versus modified bismuth quadruple therapy in Korea: a randomized controlled trial

OBJECTIVES

We aimed to compare the success rate, adverse drug events, and cost-effectiveness of tailored Helicobacter pylori eradication and modified bismuth-containing quadruple therapy.

METHODS

The diagnosis of H. pylori infection was randomly based on either rapid urease test (RUT) or dual priming oligonucleotide (DPO)-based multiplex polymerase chain reaction (PCR) in 1:1 ratio. According to the presence of point mutations that cause clarithromycin resistance, patients in the tailored therapy (TT) group received standard triple therapy or classic bismuth quadruple therapy. Patients with positive RUT results received 40 mg pantoprazole, 1000 mg amoxicillin, 750 mg metronidazole, and 600 mg bismuth subcitrate twice daily for 14 days (PAM-B therapy).

RESULTS

Between the TT (n = 141) and PAM-B groups (n = 141), H. pylori eradication rate did not differ significantly according to intention-to-treat (TT: 80.9% vs. PAM-B: 85.8%, P = 0.262), modified intention-to-treat (TT: 89.1% vs. PAM-B: 91.0%, P = 0.606), and per-protocol (TT: 89.0% vs. PAM-B: 93.5%, P = 0.198) analyses. The average cost for successful eradication was higher in the TT group than in the PAM-B group ($340.7 vs. $263.9 per patient).

CONCLUSION

PAM-B therapy exhibits similar efficacy and improved cost-effectiveness compared to TT based on the results of DPO-PCR tests.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov identifier is NCT05002595.

Scoring model for discriminating gastric cancer risk in patients with negative serum pepsinogen and anti-Helicobacter pylori antibody results

BACKGROUND

The ABC test measures serum pepsinogen and anti-Helicobacter pylori IgG antibody levels to predict precancerous conditions in the stomach and gastric cancer. However, a limitation of this test is that the gastric cancer risk is not negligible in patients with a negative result.

METHODS

Based on their ABC results, 1157 patients were classified into Groups A (n = 392), B (n = 479), C (n = 247), and D (n = 39). In Group A, 24.2% of patients had atrophic gastritis and/or intestinal metaplasia and had thus been incorrectly assigned to Group A. Patients in Group A were then assigned to derivation (n = 236) and validation (n = 156) cohorts by 3:2 random sampling. Logistic regression analyses were performed to identify the factors discriminating between a correct (true) and incorrect (false) Group A classification.

RESULTS

A 4-point discriminative model was constructed based on a high-negative H. pylori IgG antibody titer and the patient's age (50-64 and ≥65 years). The areas under the receiver operating characteristic curve for the derivation and validation cohorts were 0.868 and 0.894, respectively. In the validation cohort, the addition of a discriminative model score ≥2 to the ABC method showed a similar accuracy for predicting gastric cancer risk compared with the ABC method alone (93.8% vs. 92.4%).

CONCLUSION

The 4-point discriminative model may help identify patients with a normal serological test who are nonetheless at risk of developing gastric cancer.

Tailored eradication strategy vs concomitant therapy for Helicobacter pylori eradication treatment in Korean patients

BACKGROUND

Antibiotic resistance to Helicobacter pylori (H. pylori) infection, which ultimately results in eradication failure, has been an emerging issue in the clinical field. Recently, to overcome this problem, an antibiotic sensitivity-based tailored therapy (TT) for H. pylori infection has received attention.

AIM

To investigate the efficacy and safety profiles of TT for H. pylori infection treatment compared to a non-bismuth quadruple therapy, concomitant therapy (CT) regimen.

METHODS

We included patients (> 18 years) with an H. pylori infection and without a history of Helicobacter eradication who visited the Gil Medical Center between March 2016 and October 2020. After being randomly assigned to either the TT or CT treatment group in 1 to 1 manner, patient compliance, eradication success rate (ESR), and patient-reported side effects profiles were assessed and compared between the two groups. H. pylori infection was diagnosed using a rapid urease test, Giemsa stain, or dual priming oligonucleotide polymerase chain reaction (DPO-PCR). Tailored eradication strategy based through the presence of a 23S ribosomal RNA point mutation. For the TT group, a DPO-PCR test, which detected A2142G and/or A2143G point mutations, and a clarithromycin resistance test were performed. Patients in the clarithromycin-resistant group were treated with a bismuth-containing quadruple combination therapy, while those with sensitive results were treated with the standard triple regimen.

RESULTS

Of the 217 patients with a treatment naive H. pylori infection, 110 patients [mean age: 58.66 ± 13.03, men, n = 55 (50%)] were treated with TT, and 107 patients [mean age: 56.67 ± 10.88, men, n = 52 (48.60%)] were treated with CT. The compliance (TT vs CT, 100% vs 98.13%, P = 0.30), and follow-up loss rates (8.18% vs 9.35%, P = 0.95) were not significantly different between the groups. The ESR after treatment was also not statistically different between the groups (TT vs CT, 82.73% vs 82.24%, P = 0.95). However, the treatment-related and patient-reported side effects were significantly lower in the TT group than in the CT group (22.77% vs 50.52%, P < 0.001).

CONCLUSION

The DPO-based TT regimen shows promising results in efficacy and safety profiles as a first-line Helicobacter eradication regimen in Korea, especially when physicians are confronted with increased antibiotic resistance rates.

Types of 23S Ribosomal RNA Point Mutations and Therapeutic Outcomes for Helicobacter pylori

Background/Aims

Point mutations in the 23S ribosomal RNA gene have been associated with Helicobacter pylori clarithromycin resistance. This study aimed to detect the prevalence of these point mutations and to investigate the role of different point mutations in the success of eradication therapy.

Methods

We retrospectively investigated a total of 464 consecutive patients who underwent an endoscopic examination and dual-priming oligonucleotide-based multiplex polymerase chain reaction for H. pylori between June 2014 and October 2019. For 289 patients with negative point mutations, standard triple therapy was used in 287 patients, and the bismuth-quadruple regimen was used in two patients. For 175 patients with positive point mutations (A2142G, A2143G, and both mutations), standard triple and bismuth-quadruple therapies were used in 37 patients and 138 patients, respectively.

Results

The eradication rates of standard triple and bismuth-quadruple therapies showed no significant difference in mutation-negative patients or those with the A2142G point mutation. However, the eradication rate with bismuth-quadruple therapy was significantly higher than that with standard triple therapy in the group with the A2143G mutation or with the double mutation. The eradication rates for standard triple and bismuth-quadruple therapies, respectively, were 25.8% and 92.1% in the per-protocol group (p<0.001) and 24.2% and 85.2% in the intention-totreat analysis (p<0.001).

Conclusions

The A2143G point mutation is the most prevalent cause of clarithromycin resistance. Bismuth-quadruple therapy is superior to standard triple therapy in patients with the A2143G or double point mutation.

Evidence based guidelines for the treatment of Helicobacter pylori infection in Korea 2020

Helicobacter pylori infection is one of the most common infectious diseases worldwide. H. pylori is responsible for substantial gastrointestinal morbidity with a high disease burden. Since the revision of the H. pylori Clinical Practice Guidelines in 2013 in Korea, the eradication rate of H. pylori has gradually decreased with the use of a clarithromycin based triple therapy. According to a nationwide randomized controlled study by the Korean College of Helicobacter and Upper Gastrointestinal Research released in 2018, the intention-to-treat eradication rate was only 63.9%, which was mostly due to increased antimicrobial resistance to clarithromycin. The clinical practice guidelines for treatment of H. pylori were updated based on evidence-based medicine from a meta-analysis conducted on a target group receiving the latest level of eradication therapy. The draft recommendations developed based on the meta-analysis were finalized after expert consensus on three recommendations regarding the indication for treatment and eight recommendations on the treatment itself. These guidelines were designed to provide clinical evidence for the treatment of H. pylori to patients, nurses, medical school students, policymakers, and clinicians. These may differ from current medical insurance standards, and will be revised if more evidence emerges in the future.

Seven-day triple therapy is sufficient to eradicate infection caused by Helicobacter pylori without 23S rRNA point mutation

ABSTRACT

Tailored therapy based on dual priming oligonucleotide-based polymerase chain reaction (DPO-PCR) can be considered an alternative to overcome the low eradication rate in high clarithromycin-resistance areas. The triple therapy (TT) duration of the tailored approach in most studies was 7 days for patients without point mutation. However, recent western guidelines have recommended a treatment duration of 14 days. The aim of this study was to compare the success rate of 7 and 14 days of TT for eradicating Helicobacter pylori without point mutation, as determined by DPO-PCR.Between Feb 2016 and Feb 2019, medical records of patients who underwent DPO-PCR were reviewed. Patients without point mutation as determined by DPO-PCR were enrolled in this study. The eradication success rate and adverse events were evaluated.A total of 366 patients without A2142G and A2143G point mutation were enrolled. The success rates of 7-day and 14-day TT were 88.4% (168/190) and 85.9% (151/176) by intention to treat analysis (P = .453) and 90.8% (168/185) and 90.4% (151/167) by per-protocol analysis (P = .900), respectively. The adverse event rates showed no significant difference between the 2 groups.In patients without point mutation based on DPO-PCR results, 7-day TT is as effective as 14-day TT. Therefore, 7 days may be considered as a cost-effective treatment duration in Korea.

Evidence-Based Guidelines for the Treatment of Helicobacter pylori Infection in Korea 2020

Helicobacter pylori infection is one of the most common infectious diseases worldwide. Although the prevalence of H. pylori is gradually decreasing, approximately half of the world&#039;s population still becomes infected with this disease. H. pylori is responsible for substantial gastrointestinal morbidity worldwide, with a high disease burden. It is the most common cause of gastric and duodenal ulcers and gastric cancer. Since the revision of the H. pylori clinical practice guidelines in 2013 in Korea, the eradication rate of H. pylori has gradually decreased with the use of a clarithromycin-based triple therapy for 7 days. According to a nationwide randomized controlled study conducted by the Korean College of Helicobacter and Upper Gastrointestinal Research released in 2018, the intention-to-treat eradication rate was only 63.9%, which was mostly due to increased antimicrobial resistance, especially from clarithromycin. The clinical practice guidelines for the treatment of H. pylori were updated according to evidence-based medicine from a meta-analysis conducted on a target group receiving the latest level of eradication therapy. The draft recommendations developed based on the meta-analysis were finalized after an expert consensus on three recommendations regarding the indication for treatment and eight recommendations for the treatment itself. These guidelines were designed to provide clinical evidence for the treatment (including primary care treatment) of H. pylori infection to patients, nurses, medical school students, policymakers, and clinicians. These may differ from current medical insurance standards and will be revised if more evidence emerges in the future.

Dual Clarithromycin and Metronidazole Resistance Is the Main Cause of Failure in Ultimate Helicobacter pylori Eradication

BACKGROUND/AIM

Antimicrobial resistance significantly affects the cure rate of Helicobacter pylori (H. pylori) eradication. We evaluated the risk factor of failure in ultimate H. pylori eradication and assessed the efficacy of current regimens to overcome antibiotic resistance.

METHODS

Patients with H. pylori infection were prospectively enrolled in a single center. They were classified into 3 groups according to the previous history of H. pylori eradication, and antibiotic susceptibility was evaluated by culture and minimum inhibitory concentrations (MICs).

RESULTS

Ninety-seven patients were successfully cultured for H. pylori and 81 (83.5%), 7 (7.2%), and 9 (9.3%) were classified into primary resistance, 1st eradication failure, and 2nd or more eradication failure groups; the resistance to clarithromycin (CLA), metronidazole (MET), and levofloxacin increased in the 1st eradication failure (85.7, 57.1, and 42.9%) and 2nd or more eradication failure (88.9, 88.9, and 55.6%) groups. The prevalence of MDR was 21.0% (17/81), 57.1% (4/7), and 88.9% (8/9) in the primary, 1st eradication failure, and 2nd or more eradication failure groups, respectively. In multivariate analysis, dual CLA/MET resistance (CLA/MET-R) (OR = 31.432, 95% CI: 3.094-319.266, p = 0.004) was an independent risk factor for ultimate H. pylori eradication failure. In patients with dual CLA/MET-R, the eradication ratio of concomitant therapy was 57.1% (4/7), whereas that of bismuth-containing quadruple therapy was 27.3% (3/11) (p = 0.350).

CONCLUSIONS

Dual CLA/MET-R was the main cause of failure in ultimate H. pylori eradication, and 7-day bismuth quadruple or concomitant regimen would not be suitable for H. pylori eradication in the dual CLA/MET-R group.

Efficiency of Diagnostic Testing for Helicobacter pylori Infections-A Systematic Review

Background: The most recommended treatment for a Helicobacter pylori infection is high doses of combined antibiotics. The objective of this article is to perform a systematic review of the economic evaluation studies applied to assess the efficiency of diagnostic testing for H. pylori infections, so that their main characteristics can be identified and to learn from the literature how the antimicrobial resistance (AMR) issue is incorporated into these economic evaluations. Methods: We conducted a systematic review to compare the costs and clinical effectiveness of diagnostic strategies for H. pylori infections. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and extracted the items from the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist. Results: We found thirteen articles that were of good quality according to CHEERS: six studies focused on diagnostics of Helicobacter pylori infections associated with dyspepsia and four on duodenal ulcers. Testing was found to be the most cost-effective strategy in eight articles. Four studies considered AMR. Conclusions: Testing was more cost-effective than empirical treatment, except in cases of high prevalence (as with developing countries) or when patients could be stratified according to their comorbidities. The introduction of AMR into the model may change the efficiency of the testing strategy.

Evidence-based Guidelines for the Treatment of Helicobacter pylori Infection in Korea: 2020 Revised Edition

Helicobacter pylori (H. pylori) infection is one of the most common infectious diseases worldwide. Although its incidence is gradually decreasing, about half of the world's population still get infected. H. pylori infection is responsible for substantial gastrointestinal morbidity worldwide. It is the most common cause of gastric and duodenal ulcers as well as gastric cancer. Since the revision of the H. pylori Clinical Practice Guidelines in 2013, the eradication rate of H. pylori has gradually decreased with the use of classical triple therapy, wherein amoxicillin, clarithromycin, and proton pump inhibitors are administered, for 7 days. According to a nationwide randomized controlled study conducted by the Korean College of Helicobacter and Upper Gastrointestinal Research released in 2018, the intention-to-treat eradication rate was only 63.9%, which was due to increased antimicrobial resistance induced by the use of antibiotics, especially clarithromycin. The update of clinical practice guideline for treatment of H. pylori was developed based on evidence-based medicine by conducting a meta-analysis. The draft recommendations were finalized after expert consensus on three recommendations regarding the indication for treatment and eight recommendations on the treatment itself. These guidelines are designed to provide patients, nurses, medical school students, policymakers, and clinicians with clinical evidence to guide primary care and treatment of H. pylori infection. These may differ from current medical insurance standards and will be revised further, if necessary, based on research-based evidence.

Empirical or susceptibility-guided treatment for Helicobacter pylori infection? A comprehensive review

Although susceptibility-guided therapy is frequently recommended for Helicobacter pylori infection, the evidence available to date supporting this strategy is limited. The aim of the present article is to review the advantages and limitations of the susceptibility-guided and the empirical strategies to treat this infection. We performed a bibliographic search to identify studies investigating H. pylori susceptibility-guided therapy. Culture is not the only way to assess antibiotic resistance, as different polymerase chain reaction-based approaches have been developed as alternative methods. For detecting H. pylori antimicrobial resistance, a molecular approach based on a stool sample might enable more convenient, time-saving methods. Unfortunately, the antimicrobial susceptibility cannot be obtained in all cases. Furthermore, antibiotic susceptibility testing in clinical practice yields useful information only for a few antibiotics: clarithromycin, metronidazole, and quinolones. In addition, susceptibility towards clarithromycin and metronidazole in vitro does not necessarily lead to eradication in vivo. In the case of H. pylori therapy failure, we should not re-administer any of the antibiotics against which H. pylori has probably become resistant. Our updated meta-analysis showed that susceptibility-guided treatment is not better than empirical treatment of H. pylori infection in first-line therapy if the most updated quadruple regimens are empirically prescribed, and similar efficacy results were also demonstrated with the two strategies for second-line therapy. Cumulative H. pylori eradication rate with several successive rescue therapies empirically prescribed reaches almost 100%. Finally, the studies that have evaluated the cost-effectiveness of the susceptibility-guided treatment have achieved contradictory results. In summary, we can conclude that the evidence is too limited to support the generalized use of susceptibility-guided therapy for H. pylori treatment in routine clinical practice, either as first-line or as rescue treatment. Nevertheless, it would be recommended that susceptibility tests are performed routinely, even before prescribing first-line treatment, in specialized centers with an interest in H. pylori management.

Susceptibility-guided quadruple therapy is not superior to medication history-guided therapy for the rescue treatment of Helicobacter pylori infection: A randomized controlled trial

OBJECTIVE

In this study we aimed to compare the efficacy and safety of two personalized rescue therapies for Helicobacter pylori infection.

METHODS

An open-label, single-center, randomized controlled trial was conducted. Patients who had failed one or two regimens for H. pylori infection were randomized to receive a 14-day bismuth-containing quadruple therapy guided by antimicrobial susceptibility testing (AST) or personal medication history (PMH). In the AST group, either two of amoxicillin, clarithromycin, metronidazole or levofloxacin were prescribed according to the AST. In the PMH group, amoxicillin plus either levofloxacin or furazolidone were prescribed based on the patient's history of quinolone use. The primary outcomes were eradication rates confirmed by an urea breath test 6 weeks after treatment. The secondary outcomes were adherence, incidence of adverse events (AE) and cost-effectiveness.

RESULTS

Altogether 164 with a positive culture received AST-guided therapy and 192 received PMH-guided therapy, respectively. Both AST- and PMH-guided therapies achieved comparable eradication rate (intention-to-treat analysis: 78.10% vs 74.29%, P = 0.42; per-protocol analysis: 87.10% vs 88.64%, P = 0.80). The AST clarithromycin regimen had a lower per-protocol eradication rate than the levofloxacin (75.47% vs 96.30%, P = 0.03) or furazolidone-containing regimen (75.47% vs 92.75%, P = 0.02). Both groups had high compliance with low incidences of AE, and PMH-guided therapy had a lower medical cost.

CONCLUSIONS

AST-guided therapy was not superior to PMH-guided therapy as a second- or third-line treatment for H. pylori infection. Considering the cost-effectiveness, PMH therapy is clinically more favorable.

Helicobacter pylori "Test-and-Treat" strategy with urea breath test: A cost-effective strategy for the management of dyspepsia and the prevention of ulcer and gastric cancer in Spain-Results of the Hp-Breath initiative

BACKGROUND

Data from clinical trials comparing Helicobacter pylori (H. pylori) management strategies in patients with dyspepsia are limited. Cost-effectiveness simulation models might help to identify the optimal strategy.

OBJECTIVE

To assess the cost-effectiveness of the H. pylori "Test and Treat" (T&T) strategy including the use of urea breath test (UBT) vs symptomatic treatment (ST) and vs upper gastrointestinal endoscopy (UGE) as a first procedure in patients with dyspepsia.

METHODS

Three main strategies: "T&T" strategy including the use of UBT, "UGE" and "ST" have been compared using cost-effectiveness models developed in accordance with the Spanish medical practice. For the model simulations, a time horizon of 4 weeks was considered for the endpoint "Dyspepsia symptoms relief" and 10 years when using "Peptic ulcer avoided" and "Gastric cancer avoided" endpoints.

RESULTS

For the endpoint "Dyspepsia symptoms relief", T&T strategy appears to be the most cost-effective (883€/success) compared to UGE strategy and to ST strategy (respectively 1628€ and 990€/success). For the endpoint "Probability of peptic ulcer", the T&T strategy appears to be the most cost-effective (421€/peptic ulcer avoided/y) compared to UGE strategy and ST strategy (respectively 728€ and 632€/peptic ulcer avoided/y). For the endpoint "Gastric cancer avoided", the T&T strategy appears to be the most cost-effective (524€/gastric cancer avoided/y) compared to UGE strategy and "ST" strategy (respectively 716€ and 696€/gastric cancer avoided/y).

CONCLUSIONS

T&T strategy including the use of UBT is the most cost-effective medical approach for management of dyspepsia and for the prevention of ulcer and gastric cancer.

Best Helicobacter pylori Eradication Strategy in the Era of Antibiotic Resistance

Antibiotic resistance is the major reason for Helicobacter pylori treatment failure, and the increasing frequency of antibiotic resistance is a challenge for clinicians. Resistance to clarithromycin and metronidazole is a particular problem. The standard triple therapy (proton pump inhibitor, amoxicillin, and clarithromycin) is no longer appropriate as the first-line treatment in most areas. Recent guidelines for the treatment of H. pylori infection recommend a quadruple regimen (bismuth or non-bismuth) as the first-line therapy. This treatment strategy is effective for areas with high resistance to clarithromycin or metronidazole, but the resistance rate inevitably increases as a result of prolonged therapy with multiple antibiotics. Novel potassium-competitive acid blocker-based therapy may be effective, but the data are limited. Tailored therapy based on antimicrobial susceptibility test results is ideal. This review discussed the current important regimens for H. pylori treatment and the optimum H. pylori eradication strategy.

Optimized diagnosis of Helicobacter pylori and tailored eradication therapy for preventing gastric cancer: a proposal for SHAKE strategy

INTRODUCTION

To decrease gastric cancer-related mortality, the Korean National Cancer Screening Program provides biennial screening gastroscopy to all individuals aged >40 years. However, a test-and-treat strategy of Helicobacter pylori for preventing gastric cancer has not been established.

AREAS COVERED

In this review, we present up-to-date results of endoscopic findings of H. pylori gastritis, optimal sites for H. pylori detection, gastric cancer risk assessment using serum pepsinogen, tailored eradication based on the antimicrobial resistance against H. pylori, and post-eradication surveillance.

EXPERT OPINION

Here we propose approaches to H. pylori diagnosis and treatment for preventing gastric cancer, termed 'Screening for H. pylori in Korea and Eradication (SHAKE)' strategy. This strategy consists of the following: (1) optimized H. pylori diagnosis, (2) individualized management based on the H. pylori infection status, and (3) tailored eradication therapy. H. pylori gastritis can be diagnosed by endoscopic observation of the gastric mucosal pattern at the greater curvature of the corpus. Measurement of the serum pepsinogen I/II ratio is useful for assessing the risk of gastric cancer. As a first-line treatment, tailored eradication based on the results of molecular testing is effective in a country with a high rate of clarithromycin-resistant H. pylori.

Recent progress in Helicobacter pylori treatment

The main challenge in the field of Helicobacter pylori (H. pylori) infection is antibiotic resistance, which influences the efficacy of eradication regimens. Bismuth-containing quadruple therapy has been confirmed as an effective regimen for eradicating H. pylori, especially in strains with antibiotic resistance. High-dose proton-pump inhibitor-amoxicillin dual therapy could decrease the use of unnecessary antibiotics, which is a promising alternative approach. Adjuvant therapy (specific probiotic or vitamin) also showed good results, although more evidence is needed. Novel anti-H. pylori drugs are needed, and the establishment of the H. pylori database is an effective way to acknowledge the real-time information of H. pylori management. This review provides the recent progress of H. pylori treatment, and further studies are needed to address the role of different regimens in improving H. pylori eradication rate, especially in strains with antibiotics resistance.

Helicobacter pylori Eradication According to Sequencing-Based 23S Ribosomal RNA Point Mutation Associated with Clarithromycin Resistance

BACKGROUND/AIMS

Clarithromycin resistance in Helicobacter pylori is associated with point mutations in the 23S ribosomal RNA (rRNA) gene. We investigated the point mutations in the 23S rRNA genes of patients with clarithromycin-resistant H. pylori and compared the H. pylori eradication rates based on the point mutations.

METHODS

A total of 431 adult patients with H. pylori infection were recruited in Kangdong Sacred Heart Hospital in 2017 and 2018. Patients who did not have point mutations related to clarithromycin resistance and/or had clinically insignificant point mutations were treated with PAC (proton pump inhibitor, amoxicillin, clarithromycin) for seven days, while patients with clinically significant point mutations were treated with PAM (proton pump inhibitor, amoxicillin, metronidazole) for seven days. H. pylori eradication rates were compared.

RESULTS

Sequencing-based detection of point mutations identified four mutations that were considered clinically significant (A2142G, A2142C, A2143G, A2143C). The clarithromycin resistance rate was 21.3% in the overall group of patients. A2143G was the most clinically significant point mutation (84/431, 19.5%), while T2182C was the most clinically insignificant point mutation (283/431, 65.7%). The overall H. pylori eradication rate was 83.7%, and the seven-day PAM-treated clarithromycin-resistance group showed a significantly lower eradication rate than the seven-day PAC-treated nonresistance group (ITT; 55.4% (51/92) vs. 74.3% (252/339), p = 0.001, PP; 66.2% (51/77) vs. 88.4% (252/285), p = 0.0001).

CONCLUSIONS

There were significantly lower eradication rates in the patients with clarithromycin-resistant H. pylori when treated with PAM for seven days. A future study comparing treatment regimens in clarithromycin-resistant H. pylori-infected patients may be necessary.

Tailored eradication vs empirical bismuth-containing quadruple therapy for first-line Helicobacter pylori eradication: A comparative, open trial

BACKGROUND

Few studies have compared the efficacy and safety profile of a tailored eradication (TR) strategy based on the presence of a 23S ribosomal RNA point mutation with those of empirical bismuth-based quadruple therapy (EBQT) for first-line eradication of Helicobacter pylori (H. pylori) in Korean patients.

AIM

To compare the efficacy and safety of a TR strategy and those of EBQT regimen as first-line eradication therapy for H. pylori.

METHODS

This is an open-label, comparative study in which we prospectively enrolled patients over 18 years of age with H. pylori infection and retrospectively reviewed their data. H. pylori-positive patients diagnosed by rapid urease test, Giemsa staining, or dual priming oligonucleotide polymerase chain reaction (DPO-PCR) were enrolled from May 2016 to September 2018 at Gil Medical Center. Patients with H. pylori infection received either a TR regimen or the EBQT regimen. In the tailored therapy group that underwent DPO-PCR testing, patients with A2142G and/or A2143G point mutations were treated with a bismuth-containing quadruple regimen. The eradication rate, patient-reported side effect rate, and H. pylori eradication success rate were evaluated and compared between the groups.

RESULTS

A total of 150 patients were assigned to the TR (n = 50) or EBQT group (n = 100). The first-line eradication rate of H. pylori did not differ between the groups (96.0% vs 95.7%, P = 0.9). The rate of eradication-related side effects for TR was 12.0%, which differed significantly from that of EBQT (43.0%) for first-line treatment (P < 0.001).

CONCLUSION

DPO-PCR-based TR for H. pylori eradication may be equally efficacious, with less treatment-related complications, compared to EBQT in Korea, where clarithromycin resistance is high.

Analysis of factors associated with recovery of the serum pepsinogen ratio after Helicobacter pylori eradication: a long-term follow-up study in Korea

Objective: Serum levels of pepsinogen (PG) are related to Helicobacter pylori-induced inflammation of the gastric mucosa. This study aimed to examine the influence of H. pylori eradication on serum PG, analyze its associated factors, and evaluate the long-term outcomes.Methods: H. pylori-positive patients who underwent gastroscopy and serum PG measurement were enrolled in a single academic hospital. After H. pylori eradication, the measurement of serum PG level was performed. Recovery of serum PG I/II ratio was defined as a PG I/II ratio after eradication of >3.0 in patients with a PG I/II ratio ≤ 3.0 before eradication. Follow-up involved serum PG measurement and gastroscopy with a rapid urease test annually.Results: In all, 327 patients were eligible for study inclusion. Compared to those before H. pylori eradication, serum PG I (74.9 vs. 44.3 ng/mL, p < .001) and PG II (25.4 vs. 9.1 ng/mL, p < .001) levels significantly decreased after successful eradication. In addition, there was a significant increase in serum PG I/II ratio after eradication (3.07 vs. 4.98, p < .001). In multivariate analyses, the following were independently associated with failed recovery of serum PG I/II ratio despite successful eradication: age ≥ 60 years (odds ratio [OR] = 0.231, 95% confidence interval [CI] = 0.084-0.629, p = .004) and severe gastric atrophy (OR = 0.156, 95% CI = 0.055-0.440, p < .001).Conclusions: Recovery of serum PG I/II ratio after H. pylori eradication may be achieved in H. pylori-infected patients aged <60 years without severe gastric atrophy.

Treatment of Helicobacter pylori

PURPOSE OF REVIEW

Helicobacter pylori eradication has become more challenging over the past decade due to increasing antimicrobial resistance, especially to clarithromycin and levofloxacin. We identified 508 recent publications on H. pylori treatment (published between January 2018 and June 2019), focusing on the most highly clinically relevant for this review.

RECENT FINDINGS

Declining H. pylori eradication rates with clarithromycin triple therapy have led to most guidelines recommending 14 days bismuth-based quadruple therapy or concomitant therapy as the best initial empiric regimen. Substituting amoxicillin for tetracycline or metronidazole in quadruple therapy, and a three-in-one pill version of the regimen, also appear effective. Vonoprazan, a potent acid inhibitor, can overcome much clarithromycin resistance in triple therapy. High-dose dual therapy (proton pump inhibitor with amoxicillin) is a promising alternative approach. Reviewing resistance patterns to select suitable first-line empiric therapies is important in high resistance regions. Molecular methods to evaluate H. pylori antimicrobial susceptibility promise to be simpler than standard microbiological culture. The cost-effectiveness of antimicrobial susceptibility testing in refractory cases remains unproven.

SUMMARY

Updating clinicians treating H. pylori is important to combat the emerging problems of multidrug antimicrobial resistance in H. pylori strains. Truly novel approaches to H. pylori eradication are needed.

Eradication rate of Helicobacter pylori reinfection in Korea: A retrospective study

BACKGROUND AND AIM

Guidelines for selecting the eradication regimen for Helicobacter pylori reinfection remain unclear. This study aimed to evaluate the eradication rate of H. pylori reinfection in patients with a previous infection successfully eradicated with index triple therapy.

METHODS

This was a single-center, retrospective case-control study. A total of 10 468 H. pylori-infected patients treated with proton-pump inhibitor-based triple eradication therapy at a tertiary medical institution between 2005 and 2016 were enrolled. We reviewed the medical records of the enrolled patients and compared the treatment outcomes in those with H. pylori reinfection after a successful eradication.

RESULTS

Helicobacter pylori infection was successfully eradicated with the index triple therapy in 7770 patients (74.2%). Among 3567 patients followed up for > 1 year, H. pylori reinfection occurred in 420 (11.8%; 3.06% per person-year) during a median follow-up of 39.1 months (interquartile range, 23.5-58.7 months). Of these patients, 164 received eradication therapy for reinfection (triple therapy in 102 and quadruple therapy in 62) and had follow-up data. Triple therapy showed an eradication rate of 78.4% for H. pylori reinfection, which was not significantly different from that of the index triple therapy (P = 0.394). Quadruple therapy for reinfection exhibited a better eradication rate (87.1%) than triple therapy but without statistical significance (P = 0.237).

CONCLUSIONS

Retreatment with triple therapy for H. pylori reinfection after successful eradication of prior infection showed comparable outcomes to the index triple therapy. Bismuth-containing quadruple therapy for reinfection tended to have a better eradication rate than did triple therapy.

Review: Diagnosis of Helicobacter pylori infection

Endoscopic imaging of the stomach is improving. In addition to narrow band imaging, other methods, for example, blue light imaging and linked color imaging, are now available and can be combined with artificial intelligence systems to obtain information on the gastric mucosa and detect early gastric cancer. Immunohistochemistry is only recommended as an ancillary stain in case of chronic active gastritis without Helicobacter pylori detection by standard staining, and recommendations to exclude false negative H. pylori results have been made. Molecular methods using real-time PCR, droplet digital PCR, or amplification refractory mutation system PCR have shown a high accuracy, both for detecting H. pylori and for clarithromycin susceptibility testing, and can now be used in clinical practice for targeted therapy. The most reliable non-invasive test remains the ¹³ C-urea breath test. Large data sets show that DOB values are higher in women and that the cut-off for positivity could be decreased to 2.74 DOB. Stool antigen tests using monoclonal antibodies are widely used and may be a good alternative to UBT, particularly in countries with a high prevalence of H. pylori infection. Attempts to improve serology by looking at specific immunodominant antigens to distinguish current and past infection have been made. The interest of Gastropanel^® which also tests pepsinogen levels was confirmed.

Nationwide antibiotic resistance mapping of Helicobacter pylori in Korea: A prospective multicenter study

INTRODUCTION

The eradication rates for Helicobacter pylori have decreased in Korea although the prevalence of this bacterium has also decreased. Antibiotic resistance is likely to be a crucial factor in H. pylori eradication success, and we therefore mapped these resistance patterns nationwide in Korea.

MATERIALS AND METHODS

Five hundred and ninety adult subjects were prospectively enrolled from 2017 to 2018 from 15 centers across six geographic areas of Korea. A total of 580 biopsy tissues had been sampled from these patients during an upper endoscopy and were frozen at -80°C and delivered to a central laboratory. The agar dilution method was used to determine the minimum inhibitory concentration of amoxicillin, clarithromycin, metronidazole, tetracycline, ciprofloxacin, and levofloxacin for each H. pylori isolate.

RESULTS

The culture success rate was 60.2% (349/580). Resistance rates against clarithromycin, metronidazole, amoxicillin, tetracycline, levofloxacin, and ciprofloxacin were 17.8%, 29.5%, 9.5%, 0%, 37.0%, and 37.0%, respectively. The geographic distribution of metronidazole and quinolone resistance was highly variable. Some subjects had multiple H. pylori strains in the antrum and body of the stomach and showed a heterogeneous resistance profile between these anatomic areas. The H. pylori multidrug resistance (MDR) rate was 25.2% (88/349) among amoxicillin, clarithromycin, metronidazole, tetracycline, and quinolone and 11.2% (39/349) among four of these major antibiotics except for quinolone. The Seoul and Chungcheong areas showed a relatively lower MDR rate.

CONCLUSION

The antibiotic resistance of H. pylori differs by drug and geographic area in Korea. Detailed nationwide antibiotic resistance mapping is needed to develop an effective H. pylori eradication strategy.

Efficacy of tailored therapy for Helicobacter pylori eradication based on clarithromycin resistance and survey of previous antibiotic exposure: A single-center prospective pilot study

BACKGROUND

As the prevalence of antibiotic resistance is increasing, the effectiveness of traditional Helicobacter pylori (H pylori) therapies is gradually declining. We aimed to evaluate the efficacy of tailored therapy (dual priming oligonucleotide [DPO]-based multiplex PCR) and previous antibiotic exposure survey predicting for antibiotic resistance.

MATERIALS AND METHODS

Patients with H pylori infection who did not receive previous treatment were enrolled. The patients were divided into four groups (no resistance [NR] group, clarithromycin resistance [CLA-R] group, metronidazole-resistant [MET-R] group, and CLA- and MET-resistant [Dual-R] group) based on the results of dual priming oligonucleotide (DPO) polymerase chain reaction (PCR) and previous antibiotic exposure survey, and they were treated with tailored therapy based on antibiotic susceptibility.

RESULTS

Consecutive patients were distributed in the NR (n = 36, 70.6%), CLA-R (n = 9, 17.6%), and suspected MET-R (n = 6, 11.8%) group. The overall intention-to-treat/per-protocol eradication rate (ITT/PP) was 92.2%/94.0%. In the subgroup analysis, the ITT and PP of the NR, CLA-R, and MET-R groups were 94.4%/94.4%, 77.8%/87.5%, and 100.0%/100.0%, respectively. Total of 31 patients in all subgroups were evaluated for antibiotic resistance; five (16.1%), two (6.5%), and three (9.7%) participants showed CLA, MET, and dual resistance in culture-based susceptibility test. Compared with culture-based MIC test, the accuracy of DPO-based multiplex PCR in determining CLA resistance was 90.3%, while the accuracy of survey in determining MET resistance was only 77.4%.

CONCLUSION

A tailored therapy based on DPO-PCR and history of previous antibiotic use is useful in clinical practice and well correlated with culture-based susceptibility test.