Impact of Helicobacter pylori resistance to clarithromycin on the efficacy of the omeprazole-amoxicillin-clarithromycin therapy

Antibiotic Resistance of Helicobacter pylori in Children with Gastritis and Peptic Ulcers in Mekong Delta, Vietnam

Background: Helicobacter pylori (H. pylori) infection causes gastritis, duodenal and gastric ulcers, and gastric cancer. H. pylori eradication efficacy is low worldwide, and antibiotic resistance is the leading cause of therapy failure; therefore, this study was performed to determine the characteristics of antibiotic resistance of H. pylori in children with gastritis, duodenal and gastric ulcer. Methods: A cross-sectional study was conducted on 237 pediatric patients diagnosed with gastroduodenal inflammation and ulcer at two hospitals in Vietnam from March 2019 to April 2022. Pediatric patients with positive H. pylori tests continued to do E-tests to measure the minimum inhibitory concentration of the antibiotic so that we could prescribe effective antibiotics based on the sensitivity. Results: In 237 pediatric patients (51.1% males) with a median age of 10.3 years (range 5–16 years), endoscopic images showed that inflammatory lesions and peptic ulcers accounted for 69.2% and 30.8%, respectively. Resistance rates of H. pylori were 80.6% to clarithromycin (CLR), 71.7% to amoxicillin (AMX), 49.4% to metronidazole (MTZ), 45.1% to levofloxacin (LEV), and 11.4% to tetracycline (TET); dual resistance to AMX + CLR was 64.2%, AMX + LEV 35%, AMX + MTZ 33.3%, CLR + MTZ 32.5%, and TET + MTZ 7.2%. The frequency of clarithromycin resistance was significantly increased, particularly in pediatric patients who had received prior H. pylori treatment. The percentage of amoxicillin resistance increased with age; amoxicillin resistance of H. pylori was more prevalent among pediatric patients with peptic ulcers than those with gastroduodenal inflammation and higher in males than females. Conclusions: The proportions of resistance to CLR, AMX, MTZ, and LEV were extremely high, in contrast to TET, which was lower in pediatric patients. Our study suggests that the standard triple therapy with CLR should be limited as the empiric therapy for pediatric patients, and we should consider using eradication regimens with TET for children over 8 years of age if the medical facility is not qualified to perform antibiotic susceptibility tests of H. pylori in the Mekong Delta.

Tailored Helicobacter pylori eradication based on prior intake of macrolide antibiotics allows the use of triple therapy with optimal results in an area with high clarithromycin resistance

BACKGROUND

the previous intake of macrolide antibiotics is associated with a failure to eradicate Helicobacter pylori (H. pylori) with clarithromycin-containing regimens. However, the standard triple therapy achieves eradication rates of over 90% in patients without a previous use of macrolides in our health area. The aim of this study was to evaluate the efficacy of an H. pylori eradication strategy based on the intake of macrolides by the patient during the previous years.

METHODS

one hundred and sixty-nine patients with H. pylori infection were prospectively included in the study. The electronic medical record of each patient was reviewed at the time of inclusion. Depending on their previous intake of macrolides, patients were assigned to one of two eradication regimens: group A) patients without a previous intake of macrolides received an optimized triple therapy for 14 days; and group B) patients with a previous intake of macrolides received bismuth quadruple therapy for ten days.

RESULTS

ninety-one patients (53.84%) without a previous intake of macrolides received an optimized triple therapy (group A) and 78 patients (46.15%) with a previous intake of macrolides received bismuth quadruple therapy (group B). In group A, the H. pylori eradication rates were 90.11% in the intention-to-treat and 95.35% in the per-protocol analysis. In group B, the H. pylori eradication rates were 85.89% in the intention-to-treat and 98.5% in the per-protocol analysis. The overall eradication rates obtained using this strategy were 88.16% (95% CI: 82.32-92.02%) in the intention-to-treat and 96.75% (95% CI: 92.59-98.94%) in the per-protocol analysis.

CONCLUSIONS

an H. pylori eradication strategy based on the intake of macrolides during the previous years achieves overall eradication rates close to 90% and allows the use of standard triple therapy in more than half of the patients from a health area with a high level of clarithromycin resistance.

Antimicrobial susceptibility testing for Helicobacter pylori isolates from Brazilian children and adolescents: comparing agar dilution, E-test, and disk diffusion

Antimicrobial susceptibility testing for Helicobacter pylori is increasingly important due to resistance to the most used antimicrobials agents. Only agar dilution method is approved by CLSI, but it is difficult to perform routinely. We evaluated the reliability of E-test and disk diffusion comparing to agar dilution method on Helicobacter pylori antimicrobial susceptibility testing. Susceptibility testing was performed for amoxicillin, clarithromycin, furazolidone, metronidazole and tetracycline using E-test, disk-diffusion and agar dilution method in 77 consecutive Helicobacter pylori strains from dyspeptic children and adolescents. Resistance rates were: amoxicillin - 10.4%, 9% and 68.8%; clarithromycin - 19.5%, 20.8%, 36.3%; metronidazole - 40.2%33.7%, 38.9%, respectively by agar dilution, E-test and disk diffusion method. Furazolidone and tetracycline showed no resistance rates. Metronidazole presented strong correlation to E-test (r = 0.7992, p < 0.0001) and disk diffusion method (r=-0.6962, p < 0.0001). Clarithromycin presented moderate correlation to E-test (r = 0.6369, p < 0.0001) and disk diffusion method (r=−0.5656, p < 0.0001). Amoxicillin presented weak correlation to E-test (r = 0.3565, p = 0.0015) and disk diffusion (r=−0.3565, p = 0.0015). Tetracycline presented weak correlation with E-test (r = 0.2346, p = 0.04) and furazolidone to disk diffusion (r=−0.0288, p = 0.8038). E-test presented better agreement with gold standard. It is an easy and reliable method for Helicobacter pylori susceptibility testing. Disk diffusion method presented high disagreement and high rates of major errors.

Managing peptic ulcer and gastroesophageal reflux disease in elderly Chinese patients--focus on esomeprazole

Peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD) are not uncommon in elderly patients. Clinical presentations of these acid-related disorders may be atypical in the geriatric population. Older individuals are at increased risk for poor outcomes in complicated PUD and for development of GERD complications. Multiple risk factors (eg, Helicobacter pylori [HP], use of nonsteroidal anti-inflammatory drugs [NSAIDs], aspirin) contribute to the development of PUD. Recent data has shown that HP-negative, NSAID-negative idiopathic peptic ulcers are on the rise and carry a higher risk of recurrent ulcer bleeding and mortality. Effective management of PUD in the geriatric population relies on identification and modification of treatable risk factors. Elderly patients with GERD often require long-term acid suppressive therapy. Proton pump inhibitors (PPI) including esomeprazole are effective in the treatment of reflux esophagitis, maintenance of GERD symptomatic control, and management of PUD as well as its complications. Potential safety concerns of long-term PPI use have been reported in the literature. Clinicians should balance the risks and benefits before committing elderly patients to long-term PPI therapy.

Incidence of Helicobacter pylori infection and their clarithromycin-resistant strains in otitis media with effusion regarding phenotypic and genotypic studies

Helicobacter pylori (H. pylori) are pathogenic bacteria that infect a half of the human population, colonize gastric mucosa and can be found in gastric juice. Reflux of gastric juice has been suggested to be associated with glue ear in children. It has been suggested that tonsil and adenoid tissues are potential reservoirs of H. pylori infection. These observations raise the question as to whether H. pylori infection might have a role in otitis media with effusion (OME) in children. The objectives of this research were to evaluate the incidence and possible role of H. pylori in the pathogenesis of OME in children and to evaluate the clarithromycin-resistant strains. Molecular assessment was done to evaluate the culture results vs. molecular study. A total of 60 children, who were prone to ventilation tube insertion, adenoidectomy and/or tonsillectomy were included in the study. The control group consisted of 40 children who underwent adenoidectomy and/or tonsillectomy without the history of OME. Samples of the middle ear fluid and mucosa, adenoid tissue, tonsillar tissue and gastric lavage were cultured and underwent polymerase chain reaction (PCR) analysis then were assembled by using QIAxcel System as capillary electrophoresis for H. pylori detection. There was significant difference between the results of cultures and PCR (P < 0.05). Middle ear fluid culture was positive for H. pylori in 40% of the patients vs. 56.7% PCR results while middle ear mucosa culture was positive in 20% vs. 26.7% PCR results. Gastric lavage culture was positive in 46.6% of the patients and PCR was positive in 63.3% of the patients. Adenoid culture and PCR were positive in 56.3% for each, while tonsil culture was positive in 70% and PCR was positive in 90%. H. pylori presence in the gastric lavage, the tonsillar and adenoid tissues by culture and PCR was significantly more frequent in the study group compared to the control group. The minimum inhibitory concentration (MIC) values of clarithromycin-resistant isolates ranged from 1.5 to 8 μg/ml. This study showed the presence of H. pylori in around 50% of the patients with OME. PCR revealed its sensitivity than culture techniques. The incidence of clarithromycin resistance was found to be high among the isolates (39.6%).

Clarithromycin resistance and efficacy of clarithromycin-containing triple eradication therapy for Helicobacter pylori infection in type 2 diabetes mellitus patients

BACKGROUND

Antimicrobial resistance in Helicobacter pylori infection is an important factor leading to failure of therapy. The aim of this study was to determine the eradication rate of H pylori in type 2 diabetes mellitus and to assess the effect of clarithromycin resistance on H pylori eradication.

METHOD

Fifty-six consecutive patients with type 2 diabetes mellitus and 58 age- and sex-matched control patients were included in the study. H pylori infection was assessed by a rapid urease test and histopathological examination of biopsy specimens. Biopsies were also taken for antibiotic susceptibility testing. All enrolled patients were treated with triple therapy consisting of clarithromycin, amoxicillin, and pantoprazole for 14 days. C-13 urea breath test was performed 6 weeks after completing the triple therapy to assess eradication and associated point mutations using real-time polymerase chain reaction (PCR).

RESULTS

H pylori was eradicated in 42.9% of diabetic patients and 79.3% of control patients, (P < 0.05). In type 2 diabetes mellitus patients, clarithromycin resistance was 64.3% (36/56), while in the control group, clarithromycin resistance was 35.7% (20/58) (P < 0.05). H pylori was eradicated in 14 (70%) of the 20 clarithromycin-susceptible diabetic patients and in only 10 (27.8%) of the 36 clarithromycin-resistant diabetic patients.

CONCLUSION

The H pylori eradication rate was significantly lower and clarithromycin resistance was significantly higher in type 2 diabetics. Alternative and new treatment protocols and antibiotic susceptibility testing are needed to achieve successful eradication rates.

Efficacy and safety of faropenem in eradication therapy of Helicobacter pylori

AIMS

While triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin is the standard therapy for Helicobacter pylori eradication, it is ineffective against clarithromycin-resistant strains. To seek a better regimen for eradication therapy, we assessed the sensitivity of clinical strains seen in Japan to faropenem and then evaluated the efficacy and safety of eradication therapy containing this antibiotic.

METHODS

Minimum inhibitory concentrations (MICs) of faropenem were determined in 78 Japanese clinical H. pylori isolates using the agar dilution method. H. pylori-positive patients were consecutively assigned to a 7-day eradication therapy protocol with LAF (lansoprazole 60 mg/day, amoxicillin 2000 mg/day, and faropenem 600 mg/day), and then to a 14-day protocol. The outcomes of the therapies were assessed by (13)C-urea breath tests.

RESULTS

All 78 strains showed MICs of faropenem that were equal to or less than 0.2 microg/mL. The eradication rates according to intention-to-treat analyses were 46.5% with the 7-day therapy (n = 43) and 62.5% with the 14-day therapy (n = 32). No special measures were required to treat the adverse events observed in approximately one-third of the patients.

CONCLUSIONS

Faropenem was found to have good antimicrobial action against H. pylori in vitro. The 14-day LAF therapy successfully eradicated H. pylori in about two-thirds of the patients although the incidence of adverse events was high.

Novel genotypes in Helicobacter pylori involving domain V of the 23S rRNA gene

BACKGROUND

Helicobacter pylori is a pathogenic bacterium that infects a half of the human population. In Chile, between 55% and 79% of people are colonized by H. pylori. At present, therapeutic strategies to eradicate the bacterium depend on the knowledge of its resistance to antibiotics. The clarithromycin resistance in H. pylori is associated with point mutations in the 23S rRNA. This study analyzes 23S rRNA gene mutations and minimum inhibitory concentration (MIC) for clarithromycin in H. pylori isolates from patients of the metropolitan region of Chile.

MATERIALS AND METHODS

H. pylori isolates from 50 dyspeptic patients with no history of clarithromycin exposure were tested for clarithromycin resistance by agar dilution method. Resistant strains were analyzed for mutations in the 23S rRNA gene by polymerase chain reaction-based restriction fragment length polymorphism and sequencing.

RESULTS

Primary resistance was observed in 10 isolates (20%). A single mutation was detected in four of the 10 isolates and two or more mutations in the other six cases. The C2147G transversion and G1939A, T1942C, and A2142G transitions in the peptidyltransferase region of domain V were novel.

CONCLUSIONS

The study shows: 1, novel variants of the H. pylori 23S rRNA gene; and 2, a high prevalence of H. pylori displaying primary clarithromycin resistance with low level of MIC in an urban area of the Metropolitan Region of Chile.

American College of Gastroenterology guideline on the management of Helicobacter pylori infection

Helicobacter pylori (H. pylori) remains a prevalent, worldwide, chronic infection. Though the prevalence of this infection appears to be decreasing in many parts of the world, H. pylori remains an important factor linked to the development of peptic ulcer disease, gastric malignanc and dyspeptic symptoms. Whether to test for H. pylori in patients with functional dyspepsia, gastroesophageal reflux disease (GERD), patients taking nonsteroidal antiinflammatory drugs, with iron deficiency anemia, or who are at greater risk of developing gastric cancer remains controversial. H. pylori can be diagnosed by endoscopic or nonendoscopic methods. A variety of factors including the need for endoscopy, pretest probability of infection, local availability, and an understanding of the performance characteristics and cost of the individual tests influences choice of evaluation in a given patient. Testing to prove eradication should be performed in patients who receive treatment of H. pylori for peptic ulcer disease, individuals with persistent dyspeptic symptoms despite the test-and-treat strategy, those with H. pylori-associated MALT lymphoma, and individuals who have undergone resection of early gastric cancer. Recent studies suggest that eradication rates achieved by first-line treatment with a proton pump inhibitor (PPI), clarithromycin, and amoxicillin have decreased to 70-85%, in part due to increasing clarithromycin resistance. Eradication rates may also be lower with 7 versus 14-day regimens. Bismuth-containing quadruple regimens for 7-14 days are another first-line treatment option. Sequential therapy for 10 days has shown promise in Europe but requires validation in North America. The most commonly used salvage regimen in patients with persistent H. pylori is bismuth quadruple therapy. Recent data suggest that a PPI, levofloxacin, and amoxicillin for 10 days is more effective and better tolerated than bismuth quadruple therapy for persistent H. pylori infection, though this needs to be validated in the United States.

Helicobacter pylori eradication: a randomized prospective study of triple therapy versus triple therapy plus lactoferrin and probiotics

OBJECTIVES

Helicobacter pylori is causally associated with gastritis and peptic ulcer diseases. Recent data (meta-analysis) have demonstrated that triple therapy with amoxicillin, clarithromycin, and a proton pump inhibitor has an eradication rate of only 74-76% and new therapeutic protocols may be necessary. The aim of this study was to examine whether adding bovine lactoferrin (bLf) and probiotics (Pbs) to the standard triple therapy for H. pylori infection could improve the eradication rate and reduce side effects.

METHODS

H. pylori infection was diagnosed in 206 patients: in 107 based on an upper endoscopy exam and a rapid urease test, and in 99 by means of the H. pylori stool antigen-test and the C(13) urea breath test (C(13) UBT). The patients were randomized into two groups: 101 patients (group A) underwent standard triple eradication therapy (esomeprazole, clarithromycin, amoxicillin), while 105 patients (group B) underwent a modified eradication therapy (standard triple eradication therapy plus bLf and Pb). Successful eradication therapy was defined as a negative C(13) UBT 8 wk after completion of the treatment. Results were evaluated by intention-to-treat (ITT) and per-protocol (PP) analysis. Data were evaluated and considered positive when P<0.05.

RESULTS

At the end of the study 175/206 patients showed negative C(13) UBT results. According to intention-to-treat analysis, the infection was eradicated in 73/101 patients from Group A and in 93/105 from Group B. PP analysis showed 73/96 patients from Group A and 93/101 from Group B to have been successfully treated. More patients from group A than from group B reported side effects from their treatment (P<0.05).

CONCLUSIONS

The results of our study suggest that the addition of bLf and Pbs could improve the standard eradication therapy for H. pylori infection--bLf serving to increase the eradication rate and Pbs to reduce the side effects of antibiotic therapy.

Comparison of primary and secondary antimicrobial minimum inhibitory concentrations for Helicobacter pylori isolated from Korean patients

In this study we assessed minimum inhibitory concentration (MIC) values and resistance rates of several antibiotics in 65 primary and 324 secondary Helicobacter pylori isolates from Korean patients. Primary resistance to amoxicillin, clarithromycin, metronidazole, tetracycline, azithromycin, ciprofloxacin, levofloxacin and moxifloxacin was 18.5%, 13.8%, 66.2%, 12.3%, 32.3%, 33.8%, 21.5% and 21.5%, respectively. Secondary resistance was 31.3%, 85.1%, 70.1%, 0%, 89.6%, 35.8%, 32.8% and 32.8%, respectively. Sequence analysis of pbp1A in H. pylori strains with an amoxicillin MIC >or=2 microg/mL revealed C206T (Asp69-->Val), C1667G (Thr556-->Ser), A1684T (Asn562-->Tyr), A1777G (Thr593-->Ala) and C1798A (Pro600-->Thr) substitutions. Eleven (16.4%) of 67 treatment failures showed mixed infections with antibiotic-susceptible and -resistant H. pylori. The most common multidrug resistance profile was to clarithromycin, metronidazole and azithromycin. These results indicate that MIC values of secondary isolates were higher than those of primary isolates and that resistance to amoxicillin is probably mediated through mutations in pbp1A.

Efficacy of metronidazole as second-line drug for the treatment of Helicobacter pylori Infection in the Japanese population: a multicenter study in the Tokyo Metropolitan Area

BACKGROUND

With the increase in the frequency of clarithromycin-resistant Helicobacter pylori (H. pylori), there is rising concern about the decline of the eradication rate of this infection following treatment. The Tokyo Hp Study Group examined the eradication rate in response to a second-line regimen consisting of proton pump inhibitor (PPI), amoxicillin, and metronidazole by conducting a multicenter study in the Tokyo Metropolitan Area.

MATERIALS AND METHODS

Two hundred and twenty-eight patients with H. pylori infection, in whom the first-line therapy with a PPI, amoxicillin, and clarithromycin administered for 1 week had failed to eradicate the infection, were enrolled in this study. These cases were randomly assigned to one of the two second-line regimens containing metronidazole (PPI/AM500 or PPI/AM750) administered for 1 week. 13C-urea breath test was performed as a diagnostic method test for H. pylori infection not earlier than 8 weeks after the second-line therapy.

RESULTS

Intention-to-treat (ITT) and per-protocol (PP) analyses revealed an eradication rate of 87.6 and 90.6%, respectively, following PPI/AM500 treatment, and 86.9 and 88.6%, respectively, following PPI/AM750 treatment. Neither analysis revealed any significant difference in the eradication rate between PPI/AM500 and PPI/AM750 (p = .876 and .621, respectively). According to ITT and PP analyses, the eradication rates following treatment with PPI/AM500 were 85.2 and 88.5% with the use of lansoprazole, 62.5 and 62.5% with the use of omeprazole, and 93.2 and 96.5% with the use of rabeprazole, respectively. There was a significant difference in the eradication rates between PPI (omeprazole)/AM500 and PPI (rabeprazole)/AM500. In the case of PPI/AM750, the corresponding eradication rates were 84.8 and 87.0% with the use of lansoprazole, 92.9 and 92.9% with the use of omeprazole, and 92.9 and 92.9% with the use of rabeprazole, respectively. There were no significant differences in the eradication rates obtained with the use of the three PPIs.

CONCLUSIONS

Both PPI/AM500 and PPI/AM750 administered for 1 week appeared to be highly effective second-line regimens for the treatment of H. pylori infection in Japanese patients. From the viewpoint of adverse events, PPI/AM500 appeared to be safe compared with PPI/AM750.

Susceptibilities to clarithromycin, amoxycillin and metronidazole of Helicobacter pylori isolates from the antrum and corpus in Tokyo, Japan, 1995-2001

The aim of this study was to determine the susceptibilities to clarithromycin, amoxycillin and metronidazole of Helicobacter pylori isolates from the antrum and corpus of Japanese patients examined during the period 1995-2001. There was an increase, from 6.2% in 1995 to 22.1% in 2000-2001, in the proportion of patients infected with clarithromycin-resistant H. pylori. Of patients infected with clarithromycin-resistant H. pylori, 39.1% were infected with both clarithromycin-susceptible and -resistant H. pylori. Furthermore, the MIC90 of clarithromycin for H. pylori rose from < 1 mg/L in 1995-1998 to 8 mg/L in 1999. In contrast, the MIC90s of amoxycillin and metronidazole were < or = 0.125 and 4 mg/L, respectively, throughout the study period. The results showed that, while most H. pylori isolates were susceptible to amoxycillin and metronidazole, resistance to clarithromycin among H. pylori isolates increased markedly in Japan during 1995-2001. The results also indicated a need to test the susceptibility of H. pylori isolates from more than two samples obtained from two different sites in the stomach of a single patient in order to diagnose the presence of clarithromycin-resistant H. pylori correctly.

High levels of dual resistance to clarithromycin and metronidazole and in vitro activity of levofloxacin against Helicobacter pylori isolates from patients after failure of therapy

Current treatment for Helicobacter pylori infections generally includes two or more antimicrobials (amoxicillin, clarithromycin, nitroimidazoles, tetracycline, etc.), but treatment fails in 10-20% of all cases, often because of drug resistance. Levofloxacin has been proposed as an alternative for these refractory infections. We examined 67 H. pylori isolates from patients unsuccessfully treated with amoxicillin, clarithromycin, metronidazole and levofloxacin. Minimum inhibitory concentrations determined with the epsilometer test revealed clarithromycin and metronidazole resistance in 91 and 82.1% of the isolates, respectively; 52 (77.6%) were resistant to both drugs. All 67 isolates were susceptible to amoxicillin and tetracycline. Fifty-two isolates had levofloxacin MICs of 0.01-2 mg/l; the remaining 15 (22.4%), all clarithromycin- and metronidazole-resistant, had MICs >/= 8 mg/l. Levofloxacin may be an option for refractory H. pylori infections, but the choice should be based on in vitro susceptibility data, and physicians should consider local resistance patterns when treating these infections empirically.

Identification of a novel mutation affecting domain V of the 23S rRNA gene in Helicobacter pylori

BACKGROUND

This study analyzes clarithromycin resistance status and 23S rRNA gene mutations in Helicobacter pylori strains from Central Italian patients.

MATERIALS AND METHODS

H. pylori strains from 235 dyspeptic patients (205 with no history of clarithromycin exposure and 30 referred for failure of eradication therapy) were tested for clarithromycin resistance by screening agar method and E-test. Resistant strains were analyzed for mutations of the 23S rRNA gene by PCR-RFLP and sequencing.

RESULTS

Primary resistance was observed in strains from 43/205 (21%) patients with no history of clarithromycin exposure and secondary resistance in 30/30 (100%) strains from previously treated patients. A single mutant strain was detected in 54/73 (74%) cases, a mixture of one or more mutant(s) plus the wild type in the remaining 19/73 (26%) cases. One 23S rRNA gene mutation (A-->T transversion at nucleotide 2144) in the peptidyltransferase region of domain V was novel.

CONCLUSIONS

This study shows: (a) a high prevalence of H. pylori strains with primary or secondary clarithromycin resistance in an urban area of Central Italy; (b) colonization by both mutant and wild-type H. pylori in the same patient; (c) a novel variant of the H. pylori 23S rRNA gene.

Efficacy of two rabeprazole/gatifloxacin-based triple therapies for Helicobacter pylori infection

OBJECTIVES

To evaluate the efficacy of two novel treatment regimens consisting of gatifloxacin (400 mg daily), amoxicillin (1 g twice daily), and rabeprazole 20 mg once (RAG20) or twice daily (RAG40) given for 7 days in the eradication of Helicobacter pylori.

METHODS

Eligible patients undergoing endoscopy and having a positive rapid urease assay for H. pylori were enrolled in this open-label trial. Gastric biopsies from a random cohort of patients were cultured for H. pylori and in vitro susceptibility to gatifloxacin and amoxicillin was performed using the E-test. Compliance and side-effects were evaluated by phone calls. (14)C-urea breath tests were performed a minimum of 4 weeks after therapy and 3 weeks after any acid suppressive therapy.

RESULTS

A total of 104 patients, 52 in each group (40 females and 64 males; mean age 45.7 years) were enrolled sequentially. Eradication occurred in 43 out of 52 patients in RAG20 group (both per-protocol and intention-to-treat analysis: 83%; 95% CI: 72-93%) and in 48 of 52 patients in the RAG40 group (both per-protocol and intention-to-treat analysis: 92%; 95% CI: 85-99%). Seven patients in the RAG40 group who had previously failed one or more treatment regimens for H. pylori were cured. No significant adverse effects were reported. All 50 recovered H. pylori strains were susceptible to amoxicillin and gatifloxacin in vitro.

CONCLUSIONS

A 7-day regimen of gatifloxacin-rabeprazole-amoxicillin is effective eradication therapy for H. pylori. The use of rabeprazole twice daily results in superior eradication rates including cases of failed primary therapy. This new regimen is simple, well-tolerated, and may lead to higher compliance and lower costs.

Maastricht II treatment scheme and efficacy of different proton pump inhibitors in eradicating Helicobacter pylori

AIM: The Maastricht II criteria suggest the use of amoxicillin and clarithromycin in addition to a proton pump inhibitor over 7-10 d as a first line therapy in the eradication of Helicobacter pylori (H pylori) . For each proton pump inhibitor, various rates of eradication have been reported. The present study was to compare the efficacy of different proton pump inhibitors like omeprazole, lansoprazole and pantoprazole in combination with amoxicillin and clarithromycin in the first line eradication of H pylori and to investigate the success of H pylori eradication in our district.

METHODS: A total of 139 patients were included having a Helicobacter pylori (+) gastroduodenal disorders diagnosed by means of histology and urease test. Besides amoxicillin (1000 mg twice a day) and clarithromycin (500 mg twice a day), they were randomized to take omeprazole (20 mg twice a day), or lansoprazole (30 mg twice a day), or pantoprozole (40 mg twice a day) for 14 d. Four weeks after the therapy, the eradication was assessed by means of histology and urease test. It was evaluated as eradicated if the H pylori was found negative in both. The complaints (pain in epigastrium, nocturnal pain, pyrosis and bloating) were graded in accordance with the Licert scale. The compliance of the patients was recorded.

RESULTS: The eradication was found to be 40.8% in the omeprazole group, 43.5% in the lansoprazole group and 47.4% in the pantoprazole group. Sixty-three out of 139 patients (45%) had eradication. No statistically significant difference was observed between the groups. Significant improvements were seen in terms of the impact on the symptom scores in each group.

CONCLUSION: There was no difference between omeprazole, lansoprazole and pantoprazole in H pylori eradication, and the rate of eradication was as low as 45%. Symptoms were improved independent of the eradication in each treatment group. The low eradication rates suggest that the antibiotic resistance or the genetic differences of the microorganism might be in effect. Further studies are required to verify these suggestions.

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

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

Infection à Helicobacter pylori et résistance aux antibiotiques

PURPOSE

Seven days triple therapies combining a proton pump inhibitor (PPI) and 2 antimicrobial agents (clarithromycin [C], amoxicillin [A], metronidazole [M]), are recommended for the treatment of Helicobacter pylori infection. The eradication failures have increased these last years, particularly in France (about 30%). They are essentially related to the development of antimicrobial agents resistance, mainly concerning macrolides and nitro-imidazoles.

CURRENT KNOWLEDGE AND KEY POINTS

Primary resistance to clarithromycin is variable, but reaching now about 10% throughout the world and about 20% in France. It reduces the eradication success rate at 25%. The secondary resistance is very high, contra-indicating the use of clarithromycin in second line regimens. Primary resistance to amoxicillin has recently appeared, but remains very low until now, less than 2%, as the tetracyclin (T) resistance. Primary resistance to metronidazole is 3 times higher than macrolides resistance, but its determination is less accurate. Metronidazole resistance reduces eradication rate of about 25%, leading to the use of metronidazole in second line therapy, in increasing the triple therapy duration at 14 days (PPI-A-M), or in combination with quadruple therapy (Bismuth-PPI-T-M). Other rescue-treatments are efficacious, based on ranitidine bismuth citrate combined regimens or on rifabutine (R) based regimens (PPI-A-R).

FUTURE PROSPECTS AND PROJECTS

The recent knowledge of the mutations mainly responsible for H. pylori resistance to antimicrobial agents now allows the development of detection methods based on the study of bacterial DNA. These methods have been validated for clarithromycin and should favour in the near future the determination of resistance by the use of biopsy culture or directly on the gastric biopsy.

Beta-lactamase inhibitor enhances Helicobacter pylori eradication rate

OBJECTIVES

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

SETTING

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

SUBJECTS

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

RESULTS

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

CONCLUSIONS

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

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of primary metronidazole and clarithromycin resistance to Helicobacter pylori on omeprazole, metronidazole, and clarithromycin triple-therapy regimen in a region with high rates of metronidazole resistance

The aim of this study was to investigate the effect of metronidazole resistance (MtzR) and clarithromycin resistance (ClaR) on the eradication rate for omeprazole, clarithromycin, and metronidazole triple-therapy regimen and on the development of posttherapy drug resistance in a region of high rates of MtzR. One hundred ninety-six Helicobacter pylori isolates were recovered from patients with duodenal ulcer, gastric ulcer, or nonulcer dyspepsia during upper endoscopy. The prevalences of MtzR, ClaR, and dual resistance were 37.8%, 13.8%, and 8.7%, respectively. The intention-to-treat eradication rates for metronidazole-susceptible (87.2% vs. 67.6%; P=.001) and clarithromycin-susceptible (86.4% vs. 40.7%; P<.001) strains were significantly higher than the rates for resistant strains. Multiple logistic regression analysis implicated younger age (<40 years old), MtzR, ClaR, and the diagnosis of nonulcer dyspepsia as independent factors that predicted treatment failure. The rates of posttreatment MtzR, ClaR, and dual resistance were 88%, 88%, and 75%, respectively. MtxR and ClaR significantly affected the success of eradication therapy. Posttreatment rates of resistance were high and were related to the presence of pretreatment antibiotic resistance.

Helicobacter pylori: a microbiologist's view

Helicobacter pylori infection is known to cause a number of gastrointestinal diseases. From the standpoint of a microbiologist there are several important facets to this organism, which include the nature of the organism, it's diagnosis and the effectiveness of eradication therapy.

Primary and secondary antibiotic resistance of Helicobacter pylori strains isolated in central Italy during the years 1998-2002

BACKGROUND

Antibiotic resistance of Helicobacter pylori is the most common reason for failure in its eradication.

AIM

To determine the incidence of primary and secondary resistance to tinidazole, clarithromycin and amoxycillin in Helicobacter pylori isolates from dyspeptic patients in central Italy and to evaluate the modifications of resistance over the period from 1998 to 2002.

METHODS

H. pylori strains were isolated from antral biopsies taken during upper endoscopy in 406 dyspeptic patients with no previous therapy against H. pylori, and in 96 patients who had already undergone one or more triple therapies. Antibiotic susceptibility test was performed using the screening agar method and agar dilution method.

RESULTS

Overall primary resistance to tinidazole, clarithromycin and amoxycillin was 36.7, 23.4 and 0.2%, respectively. Secondary resistance rates were: tinidazole 69.8%, clarithromycin 82.3% and amoxycillin 1%. Resistance to clarithromycin was often associated with tinidazole resistance and was significantly higher in female patients (p<0.05). Primary and secondary antibiotic resistance did not change during the 4 years of observation.

CONCLUSIONS

The dyspeptic population with H. pylori infection in central Italy shows high levels of antibiotic resistance. Primary resistance to clarithromycin is most frequent in female patients. In patients with secondary resistance, dual resistance to clarithromycin and tinidazole is found in the majority of cases.

Helicobacter pylori: the challenge in therapy

For the therapeutic management of Helicobacter pylori infection, the Maastricht 2-2000 Consensus Report have introduced the concept of the 'treatment package' that considers first- and second-line eradication therapies together. According to this consensus statement, the first-line therapy for H. pylori eradication is a combination of the proton pump inhibitors (PPI) or ranitidine bismuth citrate (RBC) and claritromycin plus either amoxicillin or metronidazole. The second-line treatment is suggested to be PPI-quadruple therapy for a minimum of 7 days. If bismuth compounds are not available, PPI-based triple therapy will have to be used as a second-line treatment only after susceptibility testing. Since no considerable progress has been made during the past year in treatment regimens, there is still a need for new compounds that are specific for H. pylori, which could constitute future therapies.

[Microbiological factors that influence the eradication of Helicobacter pylori in adults and children]

AIM

To study microbiological factors of Helicobacter pylori, such as antimicrobial susceptibility and virulence, which affect the eradication of the microorganism in gastric mucosa of adult and pediatric patients.

METHODS

Fifty-five H. Pylori strains were isolated from culture of biopsy specimens from 39 adult and 16 pediatric patients. Antibiotic susceptibility was determined by agar dilution and study of virulence factors (cagA gene and alleles s1 and s2 of the vacA gene) by PCR. Outcome of treatment with amoxicillin (AMX), clarithromycin (CLR) and omeprazole was assessed by the urea breath test. We studied the relation of minimum inhibitory concentration (MIC) of AMX and CLR and presence of virulence factors with eradication of the microorganism.Results. The eradication rate was 69% (38/55), 71.7% in adults and 62.5% in children. Resistance to CLR and AMX was 14.5% and 0%, respectively. Overall eradication rates with respect to the variables studied were: 75% and 53% in strains with AMX MICs of < or = 0.01 6mg/L and > or = 0.032 mg/L (range < or = 0.008-0.5) (p > 0.05), 79% and 12% in strains with clarithromicina MICs of < 1 mg/L and > or = 1mg/L (range # 0.008-64) (p < 0.05), 79% and 54% in cagA+ and cagA strains (p > 0.05) and 82% and 62% in s1 and s2 strains (p > 0.05), respectively.

CONCLUSIONS

H. pylori strains with higher amoxicillin and clarithromycin MICs, and cagA and vacA s2 strains were related with lower rates of eradication in both adult and pediatric populations treated with amoxicillin, clarithromycin and omeprazole.

Validation of diffusion methods for macrolide susceptibility testing of Helicobacter pylori

Helicobacter pylori resistance to macrolides is increasing, and the need for susceptibility testing has become crucial. The only standardized method is agar dilution, which is not adapted to clinical practice. The present work aimed: (1) to optimize the technical conditions and to assess the reproducibility of the E-test and disk diffusion method for macrolides susceptibility testing of H. pylori, and (2) to assess the performances of these two phenotypic methods in detecting strains harboring a resistance mechanism to macrolides. We used 191 isolates collected in nine centers of France and Belgium. Phenotypic tests were performed on Mueller-Hinton agar supplemented with 10% horse blood, inoculated with a 2-day-old H. pylori suspension (10(8) CFU/ml), and incubated for 72 hr at 37 degrees C under microaerophilic conditions. The reproducibility studied on two randomly selected strains was better for disk diffusion than for the E-test for both clarithromycin and erythromycin. For a subset of 10 strains, the MICs of erythromycin and clarithromycin did not differ from more than one two-fold dilution when determined by E-test or agar dilution method. The breakpoints were for MICs: 1 mg/L for both clarithromycin and erythromycin and for inhibition diameters, 22 mm for clarithromycin and 17 mm for erythromycin. There was a 100% concordance between susceptibility to erythromycin and clarithromycin. However, the susceptible and resistant populations were better separated by testing erythromycin. Of 34 resistant strains, two lacked the A2142G and A2143G point mutations in 23S rRNA by PCR-RFLP. None of 15 tested sensitive strains were positive for one of these two point mutations. For clinical practice, we recommend to assess macrolide susceptibility of H. pylori by using one of these two phenotypic methods under the described technical conditions.

One-week omeprazole, furazolidone and amoxicillin rescue therapy after failure of Helicobacter pylori eradication with standard triple therapies

AIM

To test the efficacy of omeprazole, furazolidone and amoxicillin triple therapy for the treatment of Helicobacter pylori infection after failure of standard first-line therapy recommended by the Asia-Pacific Consensus on the management of H. pylori infection.

METHODS

Patients with failed H. pylori eradication received omeprazole, 20 mg, furazolidone, 100 mg, and amoxicillin, 1 g, all twice daily for 1 week. Endoscopy (CLO test, histology and culture) was performed before treatment. Post-treatment H. pylori status was determined by 13C-urea breath test 6 weeks later.

RESULTS

Fifty patients were recruited. Resistance to metronidazole, clarithromycin and both drugs was in the range of 50-64%, 60-75% and 40-50%, respectively, after failure of first-line therapy. Amoxicillin resistance was not found. The intention-to-treat and per protocol H. pylori eradication rates were 52% and 53%, respectively. Patients with double resistance to metronidazole and clarithromycin showed the lowest eradication rate (38%), which was significantly lower than that of patients with sensitive strains (88%). Side-effects were minimal and compliance was excellent (98%).

CONCLUSIONS

One-week omeprazole, furazolidone and amoxicillin rescue therapy achieved a high eradication rate in strains sensitive to metronidazole and clarithromycin. This is a cheap and safe rescue regimen when guided by pre-treatment sensitivity testing.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Rabeprazole-based 3-day and 7-day triple therapy vs. omeprazole-based 7-day triple therapy for the treatment of Helicobacter pylori infection

BACKGROUND

Rabeprazole is a new proton pump inhibitor with more potent acid suppressive and anti-Helicobacter effects.

AIM

To compare two different regimens of rabeprazole-based triple therapy vs. 7-day omeprazole-based triple therapy for the eradication of Helicobacter pylori infection.

METHOD

Patients with proven H. pylori infection were randomized to receive: (i) 7-day rabeprazole, 10 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg, all twice daily; (ii) 3-day rabeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg, all twice daily; or (iii) 7-day omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg, all twice daily. Endoscopy (CLO test, histology) was performed before randomization and 6 weeks after drug treatment.

RESULTS

One hundred and seventy-three patients were randomized. H. pylori eradication rates (intention-to-treat, n=173/per protocol, n=167) were 88%/91% for 7-day rabeprazole-based therapy, 72%/72% for 3-day rabeprazole-based therapy and 82%/89% for 7-day omeprazole-based therapy, respectively. The per protocol eradication rate was significantly better in the 7-day rabeprazole-based therapy and 7-day omeprazole-based therapy groups when compared to the 3-day rabeprazole-based therapy group (P=0.01 and P=0.04, respectively). Compliance was excellent and all three regimens were well tolerated.

CONCLUSIONS

The efficacy of seven-day rabeprazole-based triple therapy is similar to 7-day omeprazole-based triple therapy for the eradication of H. pylori infection.