Susceptibilities to different antibiotics of Helicobacter pylori strains isolated from patients at the pediatric medical center of Tehran, Iran

Sensitive dual-signal detection and effective removal of tetracycline antibiotics in honey based on a hollow triple-metal organic framework nanozymes

In this work, a colorimetric/fluorescent dual-signal mode sensor is proposed for the sensitive, selective and accurate detection and removal of tetracycline antibiotics (TCs). A triple-metal MOF of NiCoFe is successfully synthesized and controllable adjusted the shape of the hollow structure for the first time, and then modified with TCs aptamer. The as-prepared triple-atom MOF (apt-NiCoFe-MOF-74) exhibits well-defined hollow morphology, high crystallinity, and high surface areas endow their alluring adsorption and removal performances for TCs. More attractively, this triple-metal MOF show a good peroxidase-like activity and strong fluorescence property at 540 nm of apt-NiCoFe-MOF-74 when excitation wavelength was 370 nm. Inspire by this, a dual-signal output biosensor is constructed and the linear absorbance response is well correlated with wide range and low LOD for TCs. The biosensor provided an universal method with satisfactory sensitivity and accuracy for TCs analysis in real food samples.

Current Worldwide Trends in Pediatric Helicobacter pylori Antimicrobial Resistance

Helicobacter pylori (H. pylori) has acquired several resistance mechanisms in order to escape the currently used eradication regimens such as mutations that impair the replication, recombination, and transcription of DNA; the antibiotics capability to interact with protein synthesis and ribosomal activity; the adequate redox state of bacterial cells; or the penicillin-binding proteins. The aim of this review was to identify the differences in pediatric H. pylori antimicrobial-resistance trends between continents and countries of the same continent. In Asian pediatric patients, the greatest antimicrobial resistance was found to metronidazole (>50%), probably due to its wide use for parasitic infections. Aside from the increased resistance to metronidazole, the reports from different Asian countries indicated also high resistance rates to clarithromycin, suggesting that ciprofloxacin-based eradication therapy and bismuth-based quadruple therapy might be optimal choices for the eradication of H. pylori in Asian pediatric population. The scarce evidence for America revealed that H. pylori strains display an increased resistance to clarithromycin (up to 79.6%), but not all studies agreed on this statement. Pediatric patients from Africa also presented the greatest resistance rate to metronidazole (91%), but the results in terms of amoxicillin remain contradictory. Nevertheless, the lowest resistance rates in most of the African studies were found for quinolones. Among European children, the most frequent antimicrobial resistance was also noticed for metronidazole and clarithromycin (up to 59% and 45%) but with a predominance for clarithromycin as compared to other continents. The differences in antibiotic use among continents and countries worldwide is clearly responsible for the discrepancies regarding H. pylori antimicrobial-resistance patterns, emphasizing the crucial role of global judicious antibiotic use in order to control the increasing resistance rates worldwide.

The Challenges of Eradicating Pediatric Helicobacter pylori Infection in the Era of Probiotics

Helicobacter pylori (H. pylori), the most common infection of childhood, results in life-threatening complications during adulthood if left untreated. Most of these complications are related to H. pylori-induced chronic inflammation. The dysbiosis caused by H. pylori is not limited to the gastric microenvironment, but it affects the entire gastrointestinal tract. Eradication of H. pylori has recently become a real challenge for clinicians due to both the persistent increase in antibiotic resistance worldwide and the wide spectrum of side effects associated with the eradication regimens resulting; therefore, there is an urgent need for more effective and less noxious treatment options. Thus, probiotics might be a promising choice in both adults and children with H. pylori infection since their role in improving the eradication rate of this infection has been proved in multiple studies. The positive effects of probiotics might be explained by their abilities to produce antimicrobial compounds and antioxidants, alter local gastric pH, and subsequently decrease H. pylori colonization and adherence to gastric epithelial cells. Nevertheless, if used alone probiotics do not considerably increase the eradication rate.

Probiotics as the live microscopic fighters against Helicobacter pylori gastric infections

Background

Helicobacter pylori (H. pylori) is the causative agent of stomach diseases such as duodenal ulcer and gastric cancer, in this regard incomplete eradication of this bacterium has become to a serious concern. Probiotics are a group of the beneficial bacteria which increase the cure rate of H. pylori infections through various mechanisms such as competitive inhibition, co-aggregation ability, enhancing mucus production, production of bacteriocins, and modulating immune response.

Result

In this study, according to the received articles, the anti-H. pylori activities of probiotics were reviewed. Based on studies, administration of standard antibiotic therapy combined with probiotics plays an important role in the effective treatment of H. pylori infection. According to the literature, Lactobacillus casei, Lactobacillus reuteri, Lactobacillus rhamnosus GG, and Saccharomyces boulardii can effectively eradicate H. pylori infection. Our results showed that in addition to decrease gastrointestinal symptoms, probiotics can reduce the side effects of antibiotics (especially diarrhea) by altering the intestinal microbiome.

Conclusion

Nevertheless, antagonist activities of probiotics are H. pylori strain-specific. In general, these bacteria can be used for therapeutic purposes such as adjuvant therapy, drug-delivery system, as well as enhancing immune system against H. pylori infection.

Evaluation of Mutations in 23S rRNA, rdxA and frxA Genes of Helicobacter pylori in Paraffin-Embedded Gastric Biopsy Specimens from Iranian Gastric Cancer and Gastritis Patients

PURPOSE

Helicobacter pylori (H. pylori) infection is considered as one of the main cause of gastric cancer. Treatment failure of the infection often occurs due to antibiotic resistance. Herein, we aimed to evaluate the mutations in 23S rRNA gene of H. pylori which are associated with clarithromycin resistance and in rdxA and frxA genes of the bacterium which may be associated with metronidazole resistance, in paraffin-embedded gastric biopsies from patients with gastric adenocarcinoma and gastritis in Tabriz, the northwest of Iran.

METHODS

In the study, 80 paraffin-embedded tissue sections from 40 gastric cancer and 40 gastritis patients in the Imam Reza hospital, Tabriz, Iran were collected. The existence of ureC gene was verified by PCR method. Genotypical clarithromycin resistance was investigated by real-time PCR method and determination of the melting temperature. PCR reaction and sequencing were used for the evaluation of mutations in rdxA and frxA genes.

RESULTS

The results of ureC amplification showed that DNA of H. pylori was present in the 82.66% of the obtained DNA samples. About 45.16% of samples were resistant to the clarithromycin and 53.22% of them were resistant to the metronidazole. Based on the results from real-time PCR, the frequency of mutations was as follow A2143G 64.28%, A2142G 44.44% and A2142C 1.11%. The mutations of rdxA gene were 66.66% missense, 30.30% frameshift and 3.03% non-sense. The mutations of frxA gene were 36.36% missense, 54.54% frameshift and non-sense 9.09%.

CONCLUSION

A2143G mutation is the most frequent mutation among clarithromycin resistant genes in Iran. Also, missense and frameshift mutations are frequent in rdxA and frxA genes. Screening for these mutations could help researchers to investigate the most effective anti-H. pylori antibiotics and to prevent antibiotic resistance.

The increasing antimicrobial resistance of Helicobacter pylori in Iran: A systematic review and meta-analysis

BACKGROUND

Antimicrobial resistance of Helicobacter pylori can result in eradication failure. Metadata on the antimicrobial resistance of H pylori in Iran could help to formulate H pylori eradication strategies in Iran.

METHODS

A systematic review was performed after searching in MEDLINE, Scopus, Embase, Web of Science, and the Cochrane Library. A meta-analysis was performed, and a comparison of the rates between children and adults; time periods (1999-2010, 2011-2016, 2017-2019); and the methods used was carried out.

RESULTS

A total of 66 studies investigating 5936 H pylori isolates were analyzed. The weighted pooled resistance (WPR) rates were as follows: clarithromycin 21% (95% CI 16-26), metronidazole 62% (95% 57-67), clarithromycin in combination with metronidazole 16% (95% CI 10-23), ciprofloxacin 24% (95% CI 15-33), levofloxacin 18% (95% CI 9-30), erythromycin 29% (95% CI 12-50), furazolidone 13% (95% CI 4-27), tetracycline 8% (95% CI 5-13), and amoxicillin 15% (95% CI 9-22). During the three time periods, there was an increased resistance to amoxicillin, clarithromycin, ciprofloxacin, furazolidone, and tetracycline (P ˂ .05). Furazolidone and a clarithromycin/metronidazole combination had the higher resistance rates in children (P ˂ .05).

CONCLUSION

An increasing rate of resistance to amoxicillin, clarithromycin, ciprofloxacin, furazolidone, and tetracycline in Iranian H pylori isolates was identified. In children, the resistance to furazolidone and a combination of clarithromycin and metronidazole is higher compared to adults. As a stable, high resistance to metronidazole was found in children and adults in all Iranian provinces, we suggest that metronidazole should not be included in the Iranian H pylori eradication scheme.

Broad spectrum resistance in Helicobacter pylori isolated from gastric biopsies of patients with dyspepsia in Cameroon and efflux-mediated multiresistance detection in MDR isolates

Background

Antibiotic resistance is a leading cause of treatment failure in Helicobacter pylori infection. In Africa, there are very little data concerning the susceptibility of Helicobacter pylori isolates to antibiotics. The purpose of this study was to evaluate the resistance prevalence of Helicobacter pylori strains circulating in Cameroon, and to assess overexpression of efflux pump as a possible multi-drug resistance mechanisms.

Methods

A total of 140 H. pylori isolates were recovered from gastric biopsies of dyspeptic patients in two reference hospitals in Cameroon and analyzed for their antimicrobial susceptibility to amoxicillin, co-amoxiclav, ampicillin, penicillin, imipenem, metronidazole, rifabutin, erythromycin, clarithromycin, azithromycin, levofloxacin, ciprofloxacin, norfloxacin, tetracycline, doxycycline and minocycline. Antibiotic sensitivity was tested by disk diffusion method. Phe-Arg-naphthylamide (PAßN) was used as efflux pump inhibitor. INT broth microdilution method in supplemented Brain Heart Infusion broth was used to determine the MIC of ampicillin, amoxicillin, metronidazole, erythromycin, clarithromycin and doxycycline in the absence and the presence of PAßN against 32 selected MDR isolates.

Results

Overall H. pylori resistance rate was 100% to ampicillin, penicillin and co-amoxiclav; 97.14% to amoxicillin, 97.85% to metronidazole, 47.85% to erythromycin, 13.57% to clarithromycin; 5, 2.86 and 0.71% to doxycycline, tetracycline and minocycline respectively. No resistance to azithromycin, rifabutin, imipenem, ciprofloxacin, norfloxacin and levofloxacin was detected among H. pylori isolates. Seventy percent (70%) of the tested isolates elicited a multiple drugs resistance pattern; 42.57% double, 15.71% triple and 5.71% quadruple drugs resistance. Metronidazole and amoxicillin were more concerned with double resistance pattern (86.76%). The spectrum of activity recorded with metronidazole, doxycycline, clarithromycin and erythromycin ranged from 0 to 100% in the absence to the presence of PAßN against the tested MDR isolates. An 8 to 128-fold increase in potency was also noticed with these antibiotics in the presence of PAßN.

Conclusion

With regard to the high resistance rate to both amoxicillin and metronidazole, these drugs should be avoided as components of triple therapy in our milieu. In contrast, ciprofloxacin, norfloxacin, levofloxacin and tetracyclines could be used to achieve a better eradication rate and to reduce the risk of selection of H. pylori resistant strains.

Antibiotic Resistance of Helicobacter pylori in Iranian Children: A Systematic Review and Meta-Analysis

Antibiotic therapy for children infected with Helicobacter pylori is important. However, resistance to antibiotics is one of the main causes of treatment failure. This study was designed to evaluate the prevalence pattern of antibiotic resistance of H. pylori in Iranian children using a systematic review and meta-analysis of literature. A computerized search (until June 10, 2017) using related keywords in the national and international databases was performed. A total of 261 original articles on antibiotic resistance of H. pylori in Iranian children were collected. After screening for inclusion and exclusion criteria, six eligible articles were included in the meta-analysis. Resistance rates of H. pylori to different antibiotics were as follows: metronidazole: 71%, clarithromycin: 12.2%, amoxicillin: 20.4%, tetracycline: 8.4%, ampicillin: 21.4%, rifampin: 28.6%, furazolidone: 8.4%, ciprofloxacin: 16.2%, azithromycin: 19%, erythromycin: 15.3%, and nitrofurantoin: 0%. The prevalence of H. pylori resistance to metronidazole, amoxicillin, ampicillin, and rifampin among Iranian children was high. Therefore, a careful monitoring of antibiotic resistance to select the best treatment options and prevent treatment failure is required. Although resistance to some antibiotics such as clarithromycin, tetracycline, furazolidone, and ciprofloxacin was less prevalent, frequent consumption of these drugs in children should be controlled owing to their known adverse events.

Helicobacter pylori treatment: antibiotics or probiotics

Treatment of Helicobacter pylori infection is important for the management of gastrointestinal disorders such as peptic ulcer and gastric cancer. Due to the increase in the prevalence of H. pylori resistance to antibiotics, triple therapy with clarithromycin is no longer the best treatment for H. pylori, especially in some areas where the local resistance to this antibiotic is higher than 20%. Alternative treatments have been proposed for the eradication of H. pylori. Some of them including novel antibiotics or classical ones in different combinations; these treatments are being used in the regular clinical practice as novel and more effective treatments. Others therapies are using probiotics associated to antibiotics to treat this infection.The present article is a revision of H. pylori eradication treatment, focusing on emerging approaches to avoid the treatment failure, using new therapies with antimicrobials or with probiotics.

Primary Antibiotic Resistance to Helicobacter pylori Strains Isolated From Children in Northern Iran: A Single Center Study

Background:

Initial resistance to antibiotics is the main reason for the failure of Helicobacter pylori (H. pylori) eradication in children.

Objectives:

As we commonly face high antibiotic resistance rates in children, we aimed to determine the susceptibility of H. pylori to common antibiotics.

Patients and Methods:

In this cross-sectional in vitro study, 169 children younger than 14 years with clinical diagnosis of peptic ulcer underwent upper gastrointestinal endoscopy. Biopsy specimens from stomach and duodenum were cultured. In isolated colonies, tests of catalase, urease, and oxidase as well as gram staining were performed. After confirming the colonies as H. pylori, the antibiogram was obtained using disk diffusion method.

Results:

Culture for H. pylori was positive in 12.3% of the specimens, urease test in 21.3%, serological test in 18.9% and stool antigen test was positive in 21.9%. We could show high specificity but moderate sensitivity of both histological and H. pylori stool antigen tests to detect H. pylori. The overall susceptibility to metronidazole was 42.9%, amoxicillin 95.2%, clarithromycin 85.7%, furazolidone 61.9%, azithromycin 81.0%, and tetracycline 76.2% with the highest resistance to metronidazole and the lowest to clarithromycin.

Conclusions:

In our region, there is high resistance of H. pylori to some antibiotics including metronidazole and furazolidone among affected children. To reduce the prevalence of this antibiotic resistance, more controlled use of antibiotics should be considered in children.

Antimicrobial susceptibility of Canadian isolates of Helicobacter pylori in Northeastern Ontario

BACKGROUND

Helicobacter pylori plays a significant role in gastritis and ulcers. It is a carcinogen as defined by the WHO, and infection can result in adenocarcinomas and mucosa-associated lymphoid tissue lymphomas. In Canada, rates of antimicrobial resistance are relatively unknown, with very few studies conducted in the past 15 years.

OBJECTIVE

To examine rates of resistance in Sudbury, Ontario, compare antimicrobial susceptibility methods and attempt to determine the molecular basis of antibiotic resistance.

METHODS

Patients attending scheduled visits at Health Sciences North (Sudbury, Ontario) provided gastric biopsy samples on a volunteer basis. In total, 20 H pylori isolates were collected, and antimicrobial susceptibility testing (on amoxicillin, tetracycline, metronidazole, ciprofloxacin, levofloxacin and clarithromycin) was conducted using disk diffusion and E-test methods. Subsequently, genomic DNA from these isolates was sequenced to detect mutations associated with antimicrobial resistance.

RESULTS

Sixty-five percent of the isolates were found to be resistant to at least one of the listed antibiotics according to E-test. Three isolates were found to be resistant to ≥3 of the above-mentioned antibiotics. Notably, 25% of the isolates were found to be resistant to both metronidazole and clarithromycin, two antibiotics that are normally prescribed as part of first-line regimens in the treatment of H pylori infections in Canada and most of the world. Among the resistant strains, the sequences of 23S ribosomal RNA and gyrA, which are linked to clarithromycin and ciprofloxacin/levofloxacin resistance, respectively, revealed the presence of known point mutations associated with antimicrobial resistance.

CONCLUSIONS

In general, resistance to metronidazole, ciprofloxacin/levofloxacin and clarithromycin has increased since the studies in the early 2000s. These results suggest that surveillance programs of H pylori antibiotic resistance may need to be revisited or improved to prevent antimicrobial therapy failure.

Comparing the efficacy of four different protocols for eradicating of Helicobacter pylori infection in Ahvaz, southwest Iran

Introduction

Helicobacter pylori (H. pylori) is the common cause of many gastrointestinal diseases, especially peptic ulcer. Therefore, a successful treatment of this infection decreases the financial burden on health systems.

Aim

Different combinations of antibiotics are used for the eradication of this bacterium worldwide. The goal of this study is to compare the efficacy of four different protocols used for this purpose in Ahvaz.

Material and methods

A total number of 400 patients with H. pylori infection were randomly divided into four groups (100 in each): (1) OAC: omeprazole (20 mg/b.i.d.), amoxicillin (1000 mg/b.i.d.), clarithromycin (500 mg/b.i.d.) for 10 days. (2) OCF: omeprazole (20 mg/b.i.d.), ciprofloxacin (500 mg/b.i.d.), furazolidone (100 mg/b.i.d.) for 10 days. (3) OBAM: omeprazole (20 mg/b.i.d.), bismuth subcitrate (240 mg/b.i.d.), amoxicillin (1000 mg/b.i.d.), metronidazol (500 mg/b.i.d.) for 14 days. (4) OBTM: omeprazole (20 mg/b.i.d.), bismuth subcitrate (240 mg/b.i.d.), tetracycline (500 mg/b.i.d.), metronidazol (500 mg/b.i.d.) for 14 days. At the end the viability of the bacterium was assessed by C¹⁴ urea breath test.

Results

The rate of H. pylori eradication was 92%, 59%, 73%, and 76% in OAC, OCF, OBAM, and OBTM groups, respectively (based on intention to treat analysis). The eradication rate was 93.9%, 62.1%, 77.7%, and 84.4% in OAC, OCF, OBAM, and OBTM groups, respectively (based on per protocol analysis). There was a statistically significant increase in eradication rate in the OAC group in comparison with the others (p < 0.001).

Conclusions

Standard triple therapy (omeprazole, amoxicillin, clarithromycin) remains the most effective regimen for H. pylori eradication in Ahvaz.

Helicobacter pylori in Iran: A systematic review on the antibiotic resistance

OBJECTIVES

Helicobacter pylori (H. pylori) is a pathogenic bacterium that colonizes the stomachs of approximately 50% of the world's population. Resistance of H. pylori to antibiotics is considered as the main reason for the failure to eradicate this bacterium. The aim of this study was to determine the rate of resistant H. pylori strains to various antimicrobial agents in different areas of Iran.

MATERIALS AND METHODS

A systematic review of literatures on H. pylori antibiotic resistance in Iran was performed within the time span of 1997 to 2013. Data obtained from various studies were tabulated as following, 1) year of research and number strains tested, 2) number of H. pylori positive patients, 3) study place, 4) resistance of H. pylori to various antibiotics as percentage, and 5) methods used for evaluation of antibiotic resistance.

RESULTS

Over the period, a total of 21 studies on H. pylori antibiotic resistance have been conducted in different parts of Iran. In these studies, H. pylori resistance to various antibiotics, including metronidazole, clarithromycin, amoxicillin, tetracycline, ciprofloxacin, levofloxacin and furazolidone were 61.6%, 22.4%, 16.0%, 12.2%, 21.0%, 5.3% and 21.6%, respectively. We found no study on H. pylori resistance to rifabutin in Iran.

CONCLUSION

Compared to the global average, we noted that the prevalence of H. pylori resistance to metronidazole, clarithromycin, amoxicillin, and tetracycline has been rapidly growing in Iran. This study showed that in order to determine an appropriate drug regimen against H. pylori, information on antibiotic susceptibility of the bacterium within different geographical areas of Iran is required.

Analysis of Genomic Diversity among Helicobacter pylori Strains Isolated from Iranian Children by Pulsed Field Gel Electrophoresis

OBJECTIVE

Presence of genomic diversity among Helicobacter pylori (H. pylori) strains have been suggested by numerous investigators. Little is known about diversity of H. pylori strains isolated from Iranian children and their association with virulence of the strains. Our purpose was to assess the degree of genomic diversity among H. pylori strains isolated from Iranian-children, on the basis of vacA genotype, cagA status of the strains, sex, age as well as the pathological status of the patients.

METHODS

Genomic DNA from 44 unrelated H. pylori strains isolated during 1997-2009, was examined by pulse-field gel electrophoresis (PFGE). Pathological status of the patients was performed according to the modified Sydney-system and genotype/status of vacA/cagA genes was determined by PCR. PFGE was performed using XbaI restriction-endonuclease and the field inversion-gel electrophoresis system.

FINDINGS

No significant relationship was observed between the patterns of PFGE and the cagA/vacA status/genotype. Also no relationship was observed between age, sex, and pathological status of the children and the PFGE patterns of their isolates. Similar conclusion was obtained by Total Lab software. However, more relationship was observed between the strains isolated in the close period (1997-2009, 2001-2003, 2005-2007, and 2007-2009) and more difference was observed among those obtained in the distant periods (1997 and 2009).

CONCLUSION

H. pylori strains isolated from children in Iran are extremely diverse and this diversity is not related to their virulence characteristics. Occurrence of this extreme diversity may be related to adaptation of H. pylori strains to variable living conditions during transmission between various host individuals.

Prevalence of multiple drug-resistant Helicobacter pylori strains among patients with different gastric disorders in Iran

Emergence of multidrug-resistant (MDR) strains of Helicobacter pylori is a global health concern. This study was aimed to determine the frequency of MDR H. pylori strains in Iran. H. pylori isolates were obtained from cultured gastric biopsy samples on selective culture media after their characterization by PCR and conventional biochemical methods. The minimal inhibitory concentrations of rifampicin, ciprofloxacin, levofloxacin, ampicillin, clarithromycin, erythromycin, metronidazole, and tetracycline were determined for 111 strains that were isolated from 197 dyspeptic patients by the agar dilution method. The primary resistance rates were 61.3% (68/111) for metronidazole, 15.3% (17/111) for ampicillin, and 14.4% (16/111) for rifampicin. Resistance rates for other antimicrobials were as follows: macrolides (erythromycin or clarithromycin) 32.4% (36/111) and quinolones (levofloxacin or ciprofloxacin) 30.6% (34/111). Among the resistant strains, the rates of double and multiple drug resistance phenotypes were 22.6% (19/84) and 34.5% (29/84), respectively. The quadruple drug resistance phenotype encompasses 37.9% of the MDR strains, of which 90% of them was resistant to metronidazole. In conclusion, these results showed a high frequency of MDR phenotypes among the studied H. pylori strains in Iran. The eradication of the H. pylori strains presenting high resistance rates to macrolides, fluoroquinolones, or metronidazole could be achieved by approved tetracycline- or amoxicillin-containing regimens as alternative regimens to standard triple therapy.

Resistance pattern of Helicobacter pylori strains to clarithromycin, metronidazole, and amoxicillin in Isfahan, Iran

BACKGROUND

Helicobacter pylori (H. pylori) resistance to antibiotics has become a global problem and is an important factor in determining the outcome of treatment of infected patients. The purpose of this study was to determine the H. pylori resistance to clarithromycin, metronidazole, and amoxicillin in gastrointestinal disorders patients.

MATERIALS AND METHODS

In this study, a total of 260 gastric antrum biopsy specimens were collected from patients with gastrointestinal disorders who referred to Endoscopy Section of the Isfahan Hospitals. The E-test and Modified Disk Diffusion Method (MDDM) were used to verify the prevalence of antibiotic resistance in 78 H. pylori isolates to the clarithromycin, metronidazole, and amoxicillin.

RESULTS

H. pylori resistance to clarithromycin, metronidazole, and amoxicillin were 15.3, 55.1, and 6.4%, respectively. In this study, we had one multidrug resistance (MDR) isolates from patient with gastritis and peptic ulcer disease.

CONCLUSION

Information on antibiotic susceptibility profile plays an important role in empiric antibiotic treatment and management of refractive cases. According to the results obtained in this study, H. pylori resistance to clarithromycin and metronidazole was relatively high. MDR strains are emerging and will have an effect on the combination therapy.

High Helicobacter pylori resistance to metronidazole and clarithromycin in Brazilian children and adolescents

OBJECTIVE

The aim of the present study was to assess the primary and secondary resistance of Helicobacter pylori strains to clarithromycin, amoxicillin, furazolidone, tetracycline, and metronidazole, the conventional antibiotics presently used in Brazilian children and adolescents.

METHODS

Seventy-seven consecutive H pylori strains, 71 of 77 strains obtained from patients without previous eradication treatment for H pylori infection, and 6 strains from patients in whom previous eradication treatment had failed.

RESULTS

Global rate of resistance was 49.3% (38/77): 40% of strains were resistant to metronidazole, 19.5% to clarithromycin, and 10.4% to amoxicillin. All of the tested H pylori strains were susceptible to furazolidone and tetracycline. Multiple resistance were detected in 18.2% (14/77 patients) of the strains: 6 of 14 (43%) simultaneously resistant to clarithromycin and metronidazole; 5 of 14 (36%) to amoxicillin and metronidazole; 2 of 14 (14%) to amoxicillin, clarithromycin, and metronidazole; and 1 of 14 (7%) to clarithromycin and amoxicillin.

CONCLUSIONS

The high resistance rate to metronidazole and clarithromycin observed in clinical H pylori isolates can exclude these antimicrobials in empirical eradication treatment in Brazil. Otherwise, furazolidone and tetracycline presented no resistance. Properly assessing the risks and benefits, these 2 antimicrobials and their derivatives could be used in empirical eradication schedules, both associated with amoxicillin, which showed a low resistance rate despite its wide use in pediatric patients.

Primary resistance of Helicobacter pylori to levofloxacin and moxifloxacine in Iran

The increase in the prevalence of antibiotic resistance in Helicobacter pylori had a drastic effect on successful treatment. Up-to-date information on H. pylori antibiotic therapy in Iran is still limited. In this study, we aim to determine the prevalence of antibiotic resistance among the H. pylori strains. Furthermore, the possibility of using fluoroquinolones for antibiotic treatment was investigated. Antral biopsy specimens obtained from dyspeptic patients were investigated for H. pylori. Bacterial culture and susceptibility tests were done based on standard methods. H. pylori ATCC 43504 was used as a quality control. In the current study, 30 H. pylori strains were selected randomly and retested to confirm our susceptibility tests. Of 170 patients, 150 were identified as positive for H. pylori (88.2%). In this study, 150 single colonies of H. pylori strains [81 women (54%), 69 men (46%); mean age 38.6; aged 21-70 years] were collected. Primary resistance of H. pylori isolates were clarithromycin (34%), metronidazole (78.6%), tetracycline (9.3%), amoxicillin (10%), levofloxacin (5.3%) and moxifloxacine (4.6%). In conclusion, our results show that we are confronting a new generation of resistant strains of H. pylori in Iran. This alarming finding indicates an urgent need for introduction of new effective antibiotics in our country. Since the majority of clinicians prefer to continue with the ineffective antibiotics as therapeutic regimens, they must also be prepared to deal with treatment failures.

The status of antimicrobial resistance of Helicobacter pylori in Eastern Azerbaijan, Iran: comparative study according to demographics

Helicobacter pylori-associated infections are extremely common in Iran, but few data about antibiotic sensitivity of H. pylori are available for this region. The purpose of this study was to investigate the prevalence of resistance in isolates against commonly used antibiotics in Eastern Azerbaijan, Iran, and the dependence of prevalence on the sex and age of patients. H. pylori isolates were collected by culture from gastric biopsies. Antibiotic susceptibility of isolates was determined by use of the disk agar diffusion test, and the minimum inhibitory concentration of clarithromycin was established by use of the Etest. A total 395 of biopsy specimens were studied; 112 samples of H. pylori were isolated (28.3 %), 55 (49 %) from males and 57 (51 %) from females. The prevalence of resistance to clarithromycin, metronidazole, erythromycin, amoxicillin, ciprofloxacin, rifampin, nitrofurantoin, and tetracycline were 16 (14.3 %), 86 (76.8 %), 29 (26.0 %), 32 (28.6 %), 37 (33.0 %), 32 (28.6 %), 13 (11.6 %), and 21 (18.7 %), respectively. Antimicrobial resistance was not statistically significantly associated with sex or age. Furthermore, the prevalence of resistance to metronidazole was high and that to clarithromycin was reasonable, consistent with reported low success in H. pylori treatment in this area. Therefore, continuous surveillance of antibiotic resistance of H. pylori is essential.

Primary antibiotic resistance of Helicobacter pylori isolated from Beijing children

BACKGROUND

The antimicrobials resistance of Helicobacter pylori (H. pylori) was able to sharply decline the eradication rate of H. pylori both in adults and children, but there are limited studies about the primary antibiotic resistance and the related gene mutations, specifically in China.

MATERIALS AND METHODS

The primary resistance to 9 antibiotics of 73 H. pylori strains isolated from gastric biopsies of children recruited at Beijing Children's Hospital was assessed, and the mutations in 23S rRNA gene of 65 macrolide-resistant strains and in gyrA and gyrB of 12 quinolone-resistant strains were investigated.

RESULTS

The resistance rate to clarithromycin, azithromycin, metronidazole, levofloxacin, moxifloxacin, and rifampicin was 84.9%, 87.7%, 61.6%, 13.7%, 15.1%, and 6.8%, respectively. No resistance to amoxicillin, gentamicin, and tetracycline was observed. Dual, triple, and quadruple antibacterial resistant percentage was 46.6% (34/73), 15.1% (11/73), and 2.7% (2/73), respectively. The gene mutation rate of A2142C, A2142G, and A2143G in 23S rRNA gene was 1.5% (1/65), 6.2% (4/65), and 84.6% (55/65), respectively. The detection rate of mutations of Asn87, Asp91, and Met191 in GyrA was 41.7% (5/12), 25% (3/12), and 25% (3/12), respectively.

CONCLUSION

The high prevalence of primary antibiotic resistance was out of expectation in H. pylori strains isolated from the children in Beijing. Antibiotic susceptibility should be made clear before the antibiotic was used in the anti-H. pylori therapy in this population. The A2143G was the most populated mutation in macrolide-resistant strains, and Asn87 and Asp91 of GyrA were the most common mutation points in quinolone resistance strains.

Antibiotic susceptibility profile of Helicobacter pylori isolated from the dyspepsia patients in Tehran, Iran

BACKGROUND/AIM

Helicobacter pylori is an important pathogen for gastroduodenal diseases. Infection with H. pylori can be limited by regimens of multiple antimicrobial agents. However, antibiotic resistance is a leading cause of treatment failure. The aim of this study has been to determine the resistance patterns of H. pylori strains isolated from gastric biopsies of patients with dyspepsia by agar dilution method, in Tehran, Iran.

PATIENTS AND METHODS

H. pylori isolates from patients with gastrointestinal diseases were evaluated for susceptibility testing by agar dilution method. Susceptibility testing was performed to commonly used antibiotics including clarithromycin, tetracycline, amoxicillin, metronidazole and ciprofloxacin.

RESULTS

Among 92 patients with dyspepsia, H. pylori strains were isolated from 42 patients. Seventeen (40.5%) of the isolates were resistant to metronidazole (MICs ≥ 8 μg/l), whereas one isolate (2.4%) was resistant to amoxicillin (MICs ≤ 0. 5 μg/ml) and ciprofloxacin (MICs ≤ 1μg/ml). The resistance rates to other antibiotics in H. pylori isolates are recorded as follows: clarithromycin 6 (14.3 %), tetracycline 2 (4.8%). In 5 of 42 resistant cases, combined resistance was found.

CONCLUSIONS

These data suggest that metronidazole should be used among Iranian patients in first-line therapy with caution, and ciprofloxacin in association with amoxicillin and a proton pump inhibitor is more recommended.

The efficacy of a 1-week triple therapy for eradication of Helicobacter pylori infection in children

BACKGROUND AND STUDY AIMS

Poor compliance to therapy and antibiotic resistance are the main causes for failure of anti-Helicobacter pylori (H. pylori) therapy. The purpose of this study was to assess the effectiveness of omeprazole-based triple therapy in Iranian children.

PATIENTS AND METHODS

Fifty-seven children with H. pylori-related gastroduodenal disease received 1-week triple therapy with a combination of omeprazole, amoxicillin and clarithromycin (according to the susceptibility test). Success of eradication was assessed by (13)C-urea breath test and endoscopy.

RESULTS

Sixty-four patients (mean age 11.3years; range 2.7-16years) were included. Eradication was successful in 84.2% (95% confidence interval, 72.8% intention to treat).

CONCLUSION

One-week triple therapy was effective for the eradication of H. pylori infection in children.

High frequency of A2143G mutation in clarithromycin-resistant Helicobacter pylori isolates recovered from dyspeptic patients in Iran

BACKGROUND/AIM

Resistance to clarithromycin in H. pylori isolates is accepted as a main cause of treatment failure in developing countries. We aimed to determine the prevalence of clarithromycin-resistant strains isolated from dyspeptic patients in northern Iran, furthermore we aimed to assess the relationship between clinical outcomes of infection with point mutations.

MATERIALS AND METHODS

A total of 147 consecutive patients infected with H. pylori were included for determining the status of resistant H. pylori strains. With upper gastroscopy, three antral biopsies were taken from each patient, first section for rapid urea test, second for pathology and third section was used for bacterial culture in microbiologic lab. The antimicrobial susceptibility tests in this examination were agar dilution, in accordance with clinical and laboratory standards institue guidelines. Restriction fragment length polymorphism-PCR (RFLP-PCR) method was applied to determine the frequency of point mutations in 23s rRNA gene. Statistical analysis was performed using SPSS software (15.0) (SPSS, Inc., Chicago, Ill). Chi-square and Fisher's exact tests were applied to our analysis. A P value less than 5% was considered as statistically significant.

RESULTS

Our results showed that there was no point mutation in clarithromycin-susceptible strains of H. pylori.

CONCLUSION

The important findings in our study indicate that A2143G is the most prevalent point mutation (30/32: 93.7%) attributed in clarithromycin resistance among the H. pylori strains. The current study concluded that clarithromycin could still be involved in the empirical treatment of H. pylori infection, although a high frequency of A2143G mutation may increase the concerns regarding treatment failure.

Antimicrobial susceptibility of Helicobacter pylori strains isolated from patients in Shiraz, Southern Iran

AIM: To improve our understanding of Iranian regional variation in Helicobacter pylori (H. pylori) antibiotic resistance rates to find the best antibiotic therapy for eradication of H. pylori infections.

METHODS: A total of 266 patients undergoing endoscopy in Shiraz, Southern Iran, were included in this study. H. pylori strains were isolated from antral biopsies by culture and confirmed by the rapid urease-test and gram staining. Antibiotic susceptibility of H. pylori isolates was determined by E-test.

RESULTS: A total of 121 H. pylori strains were isolated, 50 from male and 71 from female patients. Data showed that 44% (n = 53), 20% (n = 24), 5% (n = 6), and 3% (n = 4) of all strains were resistant to the antibiotics metronidazole, amoxicillin, clarithromycin, and tetracycline, respectively. When the antibiotics were considered together we found 11 sensitivity patterns for the strains. Resistance to metronidazole was significantly higher in female than in male patients (P < 0.05). In about 71% of the metronidazole-resistant isolates, the minimum inhibitory concentrations (MICs) exceeded 256 μg/mL.

CONCLUSION: We found a moderate rate of primary resistance to metronidazole. However, a high MIC (> 256 mg/L) which was found in 71% of the isolates is considerable. In the case of amoxicillin, an increased resistance rate of 20% is worrying. Resistance to clarithromycin and tetracycline is also emerging among the H. pylori strains in our region.

Antibiotic resistance of Helicobacter pylori in Israeli children

OBJECTIVES

To determine the antibiotic susceptibility of Helicobacter pylori isolates from Israeli children; assess the role of previous antibiotic use in the development of antibiotic resistance and examine the possibility of simultaneous colonization of strains with different resistance patterns in the same patients.

MATERIAL AND METHODS

A prospective case-series design was used. The study group included 174 patients aged 1-18 years referred to the Schneider Children's Medical Center of Israel for gastroscopy over a 2.5-year period. Antibiotic susceptibility to amoxicillin, clarithromycin, metronidazole, tetracycline, and levofloxacin was determined by E-test on gastric biopsies (2 per patient). Clinical and demographic data were obtained by questionnaire.

RESULTS

Cultures for H. pylori yielded 55 isolates from 53 children. In treatment-naïve children, the prevalence rate of primary resistance to clarithromycin was 25% and to metronidazole, 19%. Respective rates in children previously treated for H. pylori infection were 42% (p = 0.22) and 52% (p = 0.016). Simultaneous resistance to both drugs was found in 13% of isolates (n = 7), all from children with previous treatment failure. No resistance was found to amoxicillin, tetracycline or levofloxacin. Clarithromycin resistance was associated with macrolide use for any indication during the previous year (p = 0.033). In 2 patients (3.8%), a different H. pylori strain was cultured from each biopsy.

CONCLUSIONS

H. pylori resistance to clarithromycin and metronidazole is high in Israeli children, particularly in those previously treated for H. pylori infection, in whom culture-based treatment should be considered. The simultaneous colonization of multiple strains in a minority of patients needs to be further characterized.

Frequency and molecular characteristics of ciprofloxacin- and rifampicin-resistant Helicobacter pylori from gastric infections in the UK

Treatment failure with standard Helicobacter pylori eradication regimes may require the use of 'rescue' therapies containing fluoroquinolones or rifamycins. The susceptibilities of H. pylori in the UK to such antimicrobials are unknown; therefore, this study aimed to determine the frequencies and molecular markers of resistance. Ciprofloxacin and rifampicin susceptibilities were determined by Etest and/or disc diffusion for 255 isolates of H. pylori, including 171 isolates from adult dyspeptic patients with refractive infections. Mutations in known resistance-determining regions of gyrA and rpoB were determined. The ciprofloxacin resistance rate was 7.5 %, and gyrA mutations, predominantly at codon position 91, were identified in most resistant isolates. One isolate (<1 %) had an unequivocal rifampicin-resistant phenotype by Etest yet had no associated mutations in the rpoB gene. As resistance rates were low in H. pylori isolates, including those from patients with refractive infections, it was concluded that fluoroquinolones or rifamycins might be considered in the UK for inclusion in 'rescue' therapies.

Primary resistance in Helicobacter pylori isolated in children from Iran

Helicobacter pylori-associated infection is extremely common in Iran, as in other developing countries, but few data exist on the susceptibility of H. pylori to antimicrobials commonly used in the eradication schedules in this country. This study was performed to determine the resistance rate to six antimicrobial agents used in the treatment of H. pylori infection in dyspeptic Iranian children and to recommend an updated anti-H. pylori treatment regimen to use in children. All H. pylori isolated from children who were undergoing gastroscopy were prospectively collected and subcultured to yield their susceptibility to six antimicrobial agents, by E test and disk diffusion methods. Demographic data and presenting symptoms were also collected. A prospective study was carried out from January 2003 to January 2005 with 100 strains of H. pylori isolated from children (40 girls and 60 boys; age range, 1.5 to 16 years [mean, 9.22 +/- 3.25 years]); the strains had been successfully subcultured to yield antimicrobial sensitivity. Overall the H. pylori resistance rate was 95% to metronidazole, 59% to amoxicillin, 16% to clarithromycin, 9% to furazolidone, 7% to ciprofloxacin, and 5% to tetracycline. The most common presenting symptom was abdominal pain. There were no statistically significant differences in antimicrobial resistance rates related to age, sex, or clinical presentation. In the Iranian children, the prevalence of H. pylori resistance was very high to metronidazole and amoxicillin, moderate to clarithromycin, and low to ciprofloxacin and tetracycline.

Culture of Helicobacter pylori from stool samples in children

We evaluated two protocols for isolation of Helicobacter pylori in stool from biopsied and nonbiopsied children. Twenty-three child patients whose presumptive positivity or negativity was diagnosed by endoscopy and a rapid urease test at site were used to compare biopsy-based tests with stool-based tests (H. pylori stool antigen test and stool culture). Their gastric activity and bacterial density were graded by the updated Sydney system. Biopsy and stool specimens were cultured on Campy-blood and Belo horizonte agar plates after enrichment in selective Campy-Thio medium. To compare two stool culture protocols, stools from 20 nonbiopsied children were tested by the HpSA test and cultured either as above or after treatment with cholestyramine. Grown colonies were screened by Gram staining, slide agglutination using anti-H. pylori monoclonal IgG; positive isolates were tested by biochemical tests and polymerase chain reaction for H. pylori-specific ureA gene. Coccoid H. pylori was isolated in stool samples from the biopsied patients whose bacterial density was two to four in histology. Their oxidase was slightly positive but became positive after two subcultures, while additional biochemical tests confirmed the isolation of H. pylori. Similar coccoid but oxidase positive H. pylori was isolated from three nonbiopsied children with the protocol of cholestyramine treatment only. The density of bacteria in the stomach may influence the recovery of H. pylori from stool; inactivation of bile with cholestyramine improves the yield in culture and favors isolation of an enhanced metabolic form of bacteria.

Update on fluoroquinolone resistance in Helicobacter pylori: new mutations leading to resistance and first description of a gyrA polymorphism associated with hypersusceptibility

Helicobacter pylori eradication by standard therapy is decreasing due to clarithromycin and metronidazole resistance. Fluoroquinolones are valuable drugs for alternative therapy, but their activity needs to be updated. We determined minimum inhibitory concentrations (MICs) of the newly marketed fluoroquinolones (levofloxacin, moxifloxacin and gatifloxacin) and assessed the prevalence of resistance in 128 H. pylori strains isolated in 2004-2005. The quinolone resistance-determining region (QRDR) of gyrA was sequenced for all strains. Gatifloxacin MICs (MIC(50) = 0.25 mg/L) were two- to four-fold lower than those of the other fluoroquinolones. The prevalence of resistance (ciprofloxacin MIC > 1 mg/L) was 17.2% (22 strains). All resistant strains harboured one gyrA mutation at codons 86, 87 or 91, including three new mutations (Asp86Asn, Thr87Ile and Asn87Tyr). Ciprofloxacin-susceptible strains were devoid of such gyrA mutations, but harboured a polymorphism at codon 87 that distinguished 18 isolates (17%) with a Thr87 like the reference strain J99 from 88 strains with Asn87 like the reference strain 26695. Strains with Thr87 were four-fold more susceptible to nalidixic acid, pefloxacin, ciprofloxacin and levofloxacin and were equally susceptible to moxifloxacin and gatifloxacin. The high rate of quinolone resistance in H. pylori requires the use/implication of a 'test and treat' strategy that can confidently rely on QRDR gyrA sequencing.

Does delayed gastric emptying shorten the H pylori eradication period? A double blind clinical trial

AIM: To evaluate the gastric emptying inhibitory effects of sugar and levodopa on H pylori eradication period.

METHODS: A total of 139 consecutive patients were randomized into 6 groups. The participants with peptic ulcer disease or non-ulcer dyspepsia non-responding to other medications who were also H pylori-positive patients either with positive rapid urease test (RUT) or positive histology were included. All groups were pretreated with omeprazole for 2 d and then treated with quadruple therapy regimen (omeprazole, bismuth, tetracycline and metronidazole); all drugs were given twice daily. Groups 1 and 2 were treated for 3 d, groups 3, 4 and 5 for 7 d, and group 6 for 14 d. Groups 1 to 4 received sugar in the form of 10% sucrose syrup. Levodopa was prescribed for groups 1 and 3. Patients in groups 2 and 4 were given placebo for levodopa and groups 5 and 6 received placebos for both sugar and levodopa. Upper endoscopy and biopsies were carried out before treatment and two months after treatment. Eradication of H pylori was assessed by RUT and histology 8 wk later.

RESULTS: Thirty patients were excluded. Per-protocol analysis showed successful eradication in 53% in group 1, 56% in group 2, 58% in group 3, 33.3% in group 4, 28% in group 5, and 53% in group 6. Eradication rate, patient compliance and satisfaction were not significantly different between the groups.

CONCLUSION: It seems that adding sugar or levodopa or both to anti H pylori eradication regimens may lead to shorter duration of treatment.

Tinidazole: a nitroimidazole antiprotozoal agent

BACKGROUND

Tinidazole, a structural analogue of metrondazole, is an antiprotozoal agent that has been widely used in Europe and developing countries for >2 decades with established efficacy and acceptable tolerability. It was recently approved by the US Food and Drug Administration for the treatment of trichomoniasis, giardiasis, amebiasis, and amebic liver abscess.

OBJECTIVE

This article reviews the pharmacologic and pharmacokinetic properties and clinical usefulness of tinidazole.

METHODS

Relevant information was identified through a search of MEDLINE (1966-August 2005), Iowa Drug Information Service (1966-August 2005), and International Pharmaceutical Abstracts (1970-August 2005) using the terms tinidazole, Fasigyn, and nitroimidazole.

RESULTS

In vitro, tinidazole exhibits activity against pathogenic protozoa (eg, Tricbomonas vaginalis, Entamoeba bistolytica, Giardia duodenalis), a wide range of clinically significant anaerobic bacteria (eg, Bacteroides fragilis, Clostridium difficile), and the microaerophilic bacterium Helicobacter pylori. In susceptible protozoal and bacterial cells, tinidazole is reduced to cytotoxic intermediates that covalently bind to DNA, causing irreversible damage. In human adults, tinidazole had a bioavailability of 100% and a V(d) of 50.7 L, was minimally bound to plasma protein (12%), had a plasma elimination t((1/2)) of 12.3 hours, and was eliminated primarily by hepatic metabolism (approximately 63%). Dose adjustment does not appear to be necessary on the basis of race, sex, or renal function. No data were found on the disposition of tinidazole in patients with hepatic insufficiency; therefore, use of tinidazole in patients with severe hepatic impairment (Child-Pugh class C) is not recommended. Clinical cure rates in patients with trichomoniasis, giardiasis, amebiasis, and amebic liver abscess were generally >90%. In comparative trials, tinidazole was as effective as metronidazole in the treatment of trichomoniasis and was significantly more effective than metronidazole in the treatment of giardiasis (P < 0.05) and amebiasis (P < 0.05). The most commonly reported (>1%) adverse effects included bitter taste, nausea, abdominal discomfort, anorexia, vomiting, and fatigue. The recommended dosage of tinidazole is a single dose of 2 g for trichomoniasis and giardiasis, and 2 g/d for 3 to 5 days for amebiasis.

CONCLUSIONS

Tinidazole appears to be a promising agent for the treatment of trichomoniasis, giardiasis, amebiasis, and amebic liver abscess. Clinical studies are needed to evaluate the use of tinidazole against anaerobic bacteria and H pylori.

Antimicrobial peptides are among the antagonistic metabolites produced by Bifidobacterium against Helicobacter pylori

Sixty acid-resistant Bifidobacterium isolates were recovered from human faeces and identified by genus-specific PCR and RAPD-PCR. Helicobacter pylori strains were isolated from gastric biopsies and identified by species-specific PCR. Twenty-four of the 60 Bifidobacterium isolates were considered to be different strains by RAPD-PCR. Six of the twenty-four different strains were shown to inhibit H. pylori. These antagonistic effects were related to heat-stable proteinaceous compounds, resistant to heating at 100 degrees C for 10 min, but sensitive to proteases. H. pylori stains showed variable resistance to therapeutic antibiotics (metronidazole and clarithromycin), while all the selected bifidobacteria showed intrinsic resistance to metronidazole. These potentially probiotic bifidobacteria were able to inhibit the growth of both antibiotic sensitive and resistant H. pylori strains. Thus, the synthesis of antimicrobial peptides could be one of the mechanisms of bifidobacteria to combat H. pylori infections.

Application of a stool antigen test to evaluate the incidence of Helicobacter pylori infection in children and adolescents from Tehran, Iran

Helicobacter pylori infection is acquired mainly in childhood, especially in developing countries, where a low-cost, rapid diagnostic technique which is reliable for all age groups may be useful for the management of H. pylori infection. For this purpose, we used an HpSA test (Equipar) to detect H. pylori infection in children and adolescents from Tehran, Iran. Thirty-five children who were positive or negative for H. pylori infection by endoscopy-based tests were used as positive and negative controls for the HpSA test. Stools were collected from 430 randomly selected children and adolescents (4 to 18 years old) from southwest, near the center, and northwest of Tehran. A questionnaire that included presence of recurrent abdominal pain (RAP), family history of infection and/or peptic ulcer disease (PUD), and income of parents was completed. A good agreement was found between the results of endoscopy-based tests and those of the HpSA test; the sensitivity and specificity of the Equipar-HpSA test were 100% and 83.4%, respectively. Among 430 children and adolescents, 47% were positive by the HpSA test, of whom 82% had RAP. No difference in incidence was observed between the two sexes; the various categories of age showed an increasing incidence, ranging from 24% (ages 4 to 6) to 58% (ages 16 to 18). The rate of infection in children and adolescents from the southwest was significantly higher (70%) than the rate in those from the northwest (32%), and a family history of H. pylori infection or PUD was observed in 59% of the HpSA positive subjects. The HpSA test is a useful test to detect H. pylori infection in children and adolescents from developing countries.

Role of the rdxA and frxA genes in oxygen-dependent metronidazole resistance of Helicobacter pylori

Almost 50 % of all Helicobacter pylori isolates are resistant to metronidazole, which reduces the efficacy of metronidazole-containing regimens, but does not make them completely ineffective. This discrepancy between in vitro metronidazole resistance and treatment outcome may partially be explained by changes in oxygen pressure in the gastric environment, as metronidazole-resistant (MtzR) H. pylori isolates become metronidazole-susceptible (MtzS) under low oxygen conditions in vitro. In H. pylori the rdxA and frxA genes encode reductases which are required for the activation of metronidazole, and inactivation of these genes results in metronidazole resistance. Here the role of inactivating mutations in these genes on the reversibility of metronidazole resistance under low oxygen conditions is established. Clinical H. pylori isolates containing mutations resulting in a truncated RdxA and/or FrxA protein were selected and incubated under anaerobic conditions, and the effect of these conditions on the MICs of metronidazole, amoxycillin, clarithromycin and tetracycline, and cell viability were determined. While anaerobiosis had no effect on amoxycillin, clarithromycin and tetracycline resistance, all isolates lost their metronidazole resistance when cultured under anaerobic conditions. This loss of metronidazole resistance also occurred in the presence of the protein synthesis inhibitor chloramphenicol. Thus, factor(s) that activate metronidazole under low oxygen tension are not specifically induced by low oxygen conditions, but are already present under microaerophilic conditions. As there were no significant differences in cell viability between the clinical isolates, it is likely that neither the rdxA nor the frxA gene participates in the reversibility of metronidazole resistance.

In vitro activity of fluoroquinolone and the gyrA gene mutation in Helicobacter pylori strains isolated from children

Resistance to antibiotics, especially clarithromycin, is the major cause of the failure to eradicate Helicobacter pylori. There are few studies in children concerning fluoroquinolone activity against H. pylori. Primary resistance to antibiotics including fluoroquinolones was studied in 55 H. pylori strains isolated from Japanese children. DNA sequences of the gyrA gene in fluoroquinolone-resistant strains were determined. Twelve strains (21.8%) were resistant to clarithromycin and three (5.5%) were resistant to both levofloxacin and ciprofloxacin. Out of 12 clarithromycin-resistant strains, 11 (91.7%) were susceptible to levofloxacin and ciprofloxacin. Sequence analysis in three fluoroquinolone-resistant strains showed point mutations of the gyrA gene at G271A, G271T and A272G, indicating mutations of the codon Asp91 in the fluoroquinolone-resistance-determining region of the DNA gyrase. The results suggest that fluoroquinolones should be considered as an option for second- or third-line H. pylori eradication therapy in children.