New site of modification of 23S rRNA associated with clarithromycin resistance of Helicobacter pylori clinical isolates

Molecular Surveillance of Antimicrobial Resistance of Mycobacterium leprae from Leprosy Patients in Zhejiang Province, China

Purpose

Reports on antimicrobial resistance (AMR) of Mycobacterium leprae (M. leprae) in Zhejiang Province are limited. Thus, this study aimed to investigate the drug resistance of new leprosy cases within several years and analyse the emergence of AMR mutations from Zhejiang Province.

Methods

This study enrolled 34 leprosy cases in Zhejiang Province, China, from 2018 to 2021. Gene mutation of WHO-recommended DRDRs (folP1, rpoB and gyrA) and genes of compensatory AMR-associated DRDRs, including nth, rpoA, rpoC, gyrB and 23S rRNA, were detected by amplification. Clinical data analysis was performed to investigate the epidemiological association of leprosy.

Results

Of the 34 samples, 2 (5.9%) strains showed drug resistance, which were mutated to dapsone and ofloxacin, separately. Two single mutations in gyrB were detected in different strains (5.9%), whereas one of the rpoC mutation was also detected in one strain each (2.9%), which were proved to be polymorphs. No correlation of drug resistance proportion was identified in male vs female, nerve vs no nerve involvement, deformity vs no deformity and reaction vs non-reaction cases.

Conclusion

Results showed well control of leprosy patients in Zhejiang Province. Gene mutations of WHO-recommended DRDRs folP1 and gyrA confirmed the resistance to dapsone and ofloxacin. Compensatory AMR-associated mutations confirmed to be polymorphs still require further study to determine their phenotypic outcomes in M. leprae. The results demonstrated that drug-resistant strains are not epidemic in this area. Given the few cases of leprosy, analysing the AMR of M. leprae in Zhejiang Province more comprehensively is difficult. However, regular MDT treatment and population management in the early stage may contribute to the low prevalence of leprosy.

Trends in Helicobacter pylori resistance to clarithromycin: from phenotypic to genomic approaches

For a long time Helicobacter pylori infections have been treated using the macrolide antibiotic, clarithromycin. Clarithromycin resistance is increasing worldwide and is the most common cause of H. pylori treatment failure. Here we review the mechanisms of antibiotic resistance to clarithromycin, detailing the individual and combinations of point mutations found in the 23S rRNA gene associated with resistance. Additionally, we consider the methods used to detect clarithromycin resistance, emphasizing the use of high-throughput next-generation sequencing methods, which were applied to 17 newly sequenced pairs of H. pylori strains isolated from the antrum and corpus of a recent colonized paediatric population. This set of isolates was composed of six pairs of resistant strains whose phenotype was associated with two point mutations found in the 23S rRNA gene: A2142C and A2143G. Other point mutations were found simultaneously in the same gene, but, according to our results, it is unlikely that they contribute to resistance. Further, among susceptible isolates, genomic variations compatible with mutations previously associated with clarithromycin resistance were detected. Exposure to clarithromycin may select low-frequency variants, resulting in a progressive increase in the resistance rate due to selection pressure.

Evaluation of Antibiotic Resistance of Helicobacter pylori Strains Isolated in Bari, Southern Italy, in 2017-2018 by Phenotypic and Genotyping Methods

Objective: Helicobacter pylori antibiotic resistance is a constantly evolving process and local surveillance is warranted to guide clinicians in the choice of therapy. Materials and Methods: Antibiotic susceptibility testing was performed by E-test on 92 H. pylori strains, and resistance to clarithromycin and levofloxacin was also evaluated using a commercially available genotyping method. Results: In naïve patients the resistance to clarithromycin, levofloxacin, and metronidazole was 37.7%, 26.2%, and 16.4%, respectively, significantly lower than the percentage found in treated patients. Concomitant resistance to ≥2 antibiotics was also observed in naïve patients. The A2143G mutation of the 23S-rRNA gene was the most frequently detected, also in naïve patients. The highest minimum inhibitory concentration (MIC)₅₀ value (256 mg/L) was associated with A2142 mutations in all the patients carrying them. For levofloxacin resistance a mutation in codon 87 was detected in 63.9% and in codon 91 in 36.1% of the H. pylori strains, without significant differences in the patients groups. A mutation in codon 87 was associated with the highest MIC₅₀ value (32 mg/L). Conclusions: In our area, a high prevalence of H. pylori primary resistance was detected; these rates were higher in patients who had experienced failure of several courses of therapy. A better knowledge of the local epidemiology of resistance, and the genotypes responsible, will improve the H. pylori eradication rates.

Molecular surveillance of antimicrobial resistance and transmission pattern of Mycobacterium leprae in Chinese leprosy patients

Reports on antimicrobial resistance (AMR) of Mycobacterium leprae, relationship with bacteriological index (BI), and transmission in China are limited. We investigated the emergence of AMR mutations, the relationship between BI and AMR in complete, moderate and lack of BI decline cases, and molecular epidemiological features of AMR cases by enrolling 290 leprosy cases from four endemic provinces. Seven (2.41%), one (0.34%), five (1.72%), one (0.34%), and one (0.34%) strains had single mutations in folP1, rpoC, gyrA, gyrB, and 23S rRNA, respectively. Double mutations in folP1 and gyrA, rpoB and gyrA, and gyrA and 23S rRNA were observed in one (0.34%) strain each. Mutated strains occurred in three out of 81 (95% CI-0.005-0.079, p = 0.083) cases with complete BI decline, in seven out of 103 (95% CI 0.018-0.117, p = 0.008) cases with moderate BI decline, and in four out of 34 (95% CI 0.003-0.231, p = 0.044) cases with lack of BI decline. Most of these mutated strains were geographically separated and diverged genotypically. AMR mutations may not be the main cause of the lack of BI decline. The low transmission of AMR strains at the county level indicates an ongoing transmission at close contact levels.

Detection of Helicobacter pylori with clarithromycin resistance-associated mutations using peptide nucleic acid probe-based melting point analysis

BACKGROUND

Detection of Helicobacter pylori in gastric biopsy is important for appropriate treatment and prevention of gastric carcinoma and lymphoma. A novel peptide nucleic acid probe (PNA)-based real-time polymerase chain reaction (PCR) method was developed for detection of H pylori and A2142G/A2143G mutation of the 23S rRNA gene, which is associated with clarithromycin resistance.

METHODS

To evaluate the performance of the PNA probe-based PCR method, a total of 409 gastric biopsy samples were analyzed by PNA probe-based PCR and compared with other H pylori detection methods, including hematoxylin and eosin (HE) and Warthin-Starry (WS) staining, immunohistochemistry (IHC). A2142G/A2143G mutation of the 23S rRNA gene was tested by dual priming oligonucleotide (DPO)-based PCR and Sanger sequencing to evaluate PNA probe-based PCR.

RESULTS

Among 271 cases that were positive for H pylori on IHC which was considered as a standard method, 264 cases (97.4%) and 259 cases (95.6%) were positively detected by HE/WS and PNA probe-based qPCR, respectively. Of 100 H pylori-positive patients tested by IHC, H pylori was detected in 93 cases (93.0%) by PNA probe-based PCR, 86 cases (86.0%) by DPO-based PCR, and 93 cases (93.0%) by conventional PCR. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of PNA probe-based qPCR were 93.0%, 94.9%, 93.9%, 94.9%, and 93.0%, respectively, which were all higher than those of DPO-based PCR. When Sanger sequencing was determined as a standard method to detect A2142G/A2143G mutations, the sensitivity of the PNA- and DPO-based methods was 100% and 94.4%, respectively, and the specificity was 100% for both methods.

CONCLUSION

PNA probe-based qPCR is an appropriate method for detecting H pylori and the clarithromycin resistance-associated mutation type.

Comparison of new and classical point mutations associated with clarithromycin resistance in Helicobacter pylori strains isolated from dyspeptic patients and their effects on phenotypic clarithromycin resistance

PURPOSE

We aimed to investigate the presence of three recently identified point mutations (A2115G, G2141A and A2144T) of the 23 S rRNA gene and compare them with the three most frequently encountered point mutations (A2142G, A2142C and A2143G) in Helicobacter pylori strains in Turkey.

METHODOLOGY

A total of 63 patients (mean 47.08±12.27) were included. The E-test method (for clarithromycin) was used for the clarithromycin antimicrobial susceptibility test of isolated H. pylori strains. Real-time PCR was used to detect the point mutations.

RESULTS

A total of 24 out of 63 H. pylori strains (38.1%) were detected as clarithromycin resistant (>0.5 mg l^-1 ). The new A2115G (n:6, 25%), A2144T (n:7, 29.1%) and G2141A, 8 (n:8, 33.3%) mutations and the classical A2142G (n:8, 33.3%) and A2143G (n:11, 45.8%) point mutations were detected in the 24 clarithromycin-resistant strains. The A2144T point mutation had the highest median MIC value (3 mg l^-1 ) amongst the new mutations, but the classical mutations (A2142G and A2143G) had the highest median MIC values (256 mg l^-1 ) overall. The presence of the A2115G (OR:31.66), A2144T (OR:36.92) or G2141A (OR:28.16) mutations increased the likelihood of clarithromycin resistance in H. pylori strains by 31.66-, 36.92- and 28.16-fold (ORs), respectively, according to the binary logistic regression analysis.

CONCLUSION

We concluded that classical mutations of the 23 S rRNA gene resulted in higher clarithromycin MIC values than new mutations. These new point mutations caused moderate elevations in the MIC values of clarithromycin-resistant H. pylori strains.

Droplet Digital PCR-Based Detection of Clarithromycin Resistance in Helicobacter pylori Isolates Reveals Frequent Heteroresistance

Chronic infection with Helicobacter pylori causes peptic ulcers and stomach cancer in a subset of infected individuals. While standard eradication therapy includes multiple antibiotics, treatment failure due to resistance is an increasing clinical problem. Accurate assessment of H. pylori antimicrobial resistance has been limited by slow growth and sampling of few isolates per subject. We established a method to simultaneously quantify H. pylori clarithromycin-resistant (mutant) and -susceptible (wild-type) 23S rRNA gene alleles in both stomach and stool samples using droplet digital PCR (ddPCR). In 49 subjects, we assessed the performance of these assays alongside clarithromycin MIC testing of up to 16 H. pylori isolates per subject and included both cancer (25 subjects) and noncancer (24 subjects) cases. Gastric ddPCR and H. pylori culture showed agreement with urea breath test (UBT) detection of infection in 94% and 88% of subjects, respectively, while stool ddPCR showed agreement with UBT in 92% of subjects. Based on MIC testing of 43 culture-positive cases, 20 subjects had only susceptible isolates, 14 had a mix of susceptible and resistant isolates, and 9 had only resistant isolates. ddPCR of gastric samples indicated that 21 subjects had only wild-type alleles, 13 had a mixed genotype, and 9 had only mutant alleles. Stool ddPCR detected mutant alleles in four subjects for which mutant alleles were not detected by stomach ddPCR, and no resistant isolates were cultured. Our results indicate that ddPCR detects H. pylori clarithromycin resistance-associated genotypes, especially in the context of heteroresistance.

Application of next-generation sequencing to characterize novel mutations in clarithromycin-susceptible Helicobacter pylori strains with A2143G of 23S rRNA gene

Background

Clarithromycin (CLR) resistance has become a predominant factor for treatment failure of Helicobacter pylori eradication. Although the molecular mechanism of CLR resistance has been clearly understood in H. pylori, it is lack of evidence of other genes involved in drug resistance. Furthermore, the molecular mechanism of phenotype susceptible to CLR while genotype of 23S rRNA is mutant with A2143G is unclear. Here, we characterized the mutations of CLR-resistant and -susceptible H. pylori strains to explore bacterial resistance.

Methods

In the present study, the whole genomes of twelve clinical isolated H. pylori strains were sequenced, including two CLR-susceptible strains with mutation of A2143G. Single nucleotide variants (SNVs) were extracted and analyzed from multidrug efflux transporter genes.

Results

We did not find mutations associated with known CLR-resistant sites except for controversial T2182C outside of A2143G in the 23S rRNA gene. Although total SNVs of multidrug efflux transporter gene and the SNVs of HP0605 were significant differences (P ≤ 0.05) between phenotype resistant and susceptible strains. There is no significant difference in SNVs of RND or MFS (HP1181) family. However, the number of mutations in the RND family was significantly higher in the mutant strain (A2143G) than in the wild type. In addition, three special variations from two membrane proteins of mtrC and hefD were identified in both CLR-susceptible strains with A2143G.

Conclusions

Next-generation sequencing is a practical strategy for analyzing genomic variation associated with antibiotic resistance in H. pylori. The variations of membrane proteins of the RND family may be able to participate in the regulation of clinical isolated H. pylori susceptibility profiles.

Prevalence of Primary Resistance of Helicobacter pylori to Clarithromycin and Levofloxacin in Southern Spain

BACKGROUND

The eradication of Helicobacter pylori (HP) using clarithromycin (CLA)-based triple therapy depends on the resistance of HP to antibiotics. The Maastricht III conference recommends the implementation of locoregional surveillance programmes for primary resistance of HP to CLA. In Andalusia, there are no previous data in this respect. The aim of this study was to determine the prevalence of the primary resistance of HP to CLA and levofloxacin (LF) in southern Spain.

METHODS

Multicentre cross sectional study was carried out in 6 hospitals in Andalusia. Patients of both sexes numbering 401 were included (male 48%), aged 18-80 years and naïve to HP eradication. Resistance of HP to CLA (CLAr) and LF (LFr) was assessed by determining mutations by PCR: mutations of the 23S rRNA gene define CLAr and mutations of the gene gyrA define LFr. Four hundred one gastric samples were collected. CLAr was detected in 72 patients (17.9%) and LFr was detected in 56 patients (13.9%). Heteroresistance was detected for both antibiotics: CLA 37/72 (51.3%) and LF 28/56 (50%). Variability for CLAr was detected among the centres, ranging from 11.5% to 24.7% without statistical significance (p = 0.12). Female sex was related to CLAr.

CONCLUSIONS

In Andalusia, there is a high rate of primary CLAr and LFr. CLA-based triple therapy should be avoided as the primary eradication regimen in this region. There is a wide variability in the rate of CLAr among centres.

Rapid identification of Helicobacter pylori and assessment of clarithromycin susceptibility from clinical specimens using FISH

Helicobacter pylori remains one of the most common bacterial infections worldwide. Clarithromycin resistance is the most important cause of H. pylori eradication failures. Effective antibiotic therapies in H. pylori infection must be rapidly adapted to local resistance patterns. We investigated the prevalence of clarithromycin resistance due to mutations in positions 2142 and 2143 of 23SrRNA gene of H. pylori by fluorescence in situ hybridisation (FISH), and compared with culture and antimicrobial susceptibility testing in 234 adult patients with dyspepsia who were enrolled. Antrum and corpus biopsy specimens were obtained for rapid urease test, histopathology and culture. Epsilometer test was used to assess clarithromycin susceptibility. H. pylori presence and clarithromycin susceptibility were determined by FISH in paraffin‐embedded biopsy specimens. We found that 164 (70.1%) patients were positive for H. pylori based on clinical criteria, 114 (69.5% CI 62.5–76.6%) were culture positive, and 137 (83.5% CI 77.8–89.2%) were FISH positive. Thus the sensitivity of FISH was significantly superior to that of culture. However specificity was not significantly different (91.4 versus 100.0%, respectively). The resistance rate to clarithromycin for both antrum and corpus was detected in H. pylori‐positive patients; 20.2% by FISH and 28.0% by E‐test.The concordance between E‐test and FISH was only 89.5% due to the presence of point mutations different from A2143G, A2142G or A2142C. We conclude that FISH is significantly more sensitive than culture and the E‐test for the detection of H. pylori and for rapid determinination of claritromycin susceptibility. The superior hybridisation efficiency of FISH is becoming an emerging molecular tool as a reliable, rapid and sensitive method for the detection and visualisation of H. pylori, especially when the management of H. pylori eradication therapy is necessary. This is particularly important for the treatment of patients with H. pylori eradication failure.

Helicobacter pylori and Antibiotic Resistance, A Continuing and Intractable Problem

Helicobacter pylori, a human pathogen with a high global prevalence, is the causative pathogen for multiple gastrointestinal diseases, especially chronic gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue lymphoma, and gastric malignancies. Antibiotic therapies remain the mainstay for H. pylori eradication; however, this strategy is hampered by the emergence and spread of H. pylori antibiotic resistance. Exploring the mechanistic basis of this resistance is becoming one of the major research questions in contemporary biomedical research, as such knowledge could be exploited to devise novel rational avenues for counteracting the existing resistance and devising strategies to avoid the development of a novel anti-H. pylori medication. Encouragingly, important progress in this field has been made recently. Here, we attempt to review the current state and progress with respect to the molecular mechanism of antibiotic resistance for H. pylori. A picture is emerging in which mutations of various genes in H. pylori, resulting in decreased membrane permeability, altered oxidation-reduction potential, and a more efficient efflux pump system. The increased knowledge on these mechanisms produces hope that antibiotic resistance in H. pylori can ultimately be countered.

Occurrence of Mutations in the Antimicrobial Target Genes Related to Levofloxacin, Clarithromycin, and Amoxicillin Resistance in Helicobacter pylori Isolates from Buenos Aires City

Domain V of 23S rRNA, gyrA and gyrB Quinolones Resistance-Determining Region (QRDR), and pbp-1A gene point mutations were investigated in Helicobacter pylori-resistant isolates from three centres of Buenos Aires. Minimal inhibitory concentrations (MICs) were performed in 197 isolates from 52 H. pylori-positive naive patients by agar dilution method. Point mutations were achieved by amplification and sequencing of the target genes, and their association with resistance was determined by natural transformation assays. Resistance rates were as follows: metronidazole 28.8%, clarithromycin (CLA) 26.9%, levofloxacin (LEV) 32.7%, and amoxicillin (AMX) 7.6%. Nearly one-third of patients carried multidrug-resistant isolates. A2143G or A2142G in domain V of 23S-rRNA was found in all isolates showing high level of resistance to CLA (MIC >2 mg/L), accounting for 76.0% (38/50) of those with the resistant phenotype. The mutations A2267G or T1861C carried by 8/12 isolates with MIC 1-2 mg/L (low level) did not confer resistance by transformation. Substitutions at GyrA position 87 or 91, mainly N87K and D91G, were found in 92.8% (52/56) of the LEV-resistant isolates: 48 isolates with MIC 4-64 mg/L and 4/8 isolates with MIC 2 mg/L. The remaining four harboured K133N, also present in susceptible isolates. None of the substitutions in GyrB demonstrated to confer resistance. Transformation proved that PBP-1A N562Y and/or T556S substitutions confer the AMX resistance in our isolates, showing an additive effect. In conclusion, the usually reported mutations related to CLA, LEV, and AMX resistance were found in our isolates. However, low-level CLA resistance seems not to be due to mutations in Domain V of 23S rRNA gene.

Mutations affecting domain V of the 23S rRNA gene in Helicobacter pylori from Cairo, Egypt

BACKGROUND

Clarithromycin is a main component of the recommended first-line triple therapy for Helicobacter pylori in Egypt. We aimed in our study to investigate the prevalence of clarithromycin-resistant H. pylori strains due to the point mutations at domain V of the H. pylori 23S rRNA among the Egyptian population using the polymerase chain reaction/restricted fragment length polymorphism (PCR/RFLP) assay.

METHODS

Gastric biopsies obtained from 100 dyspeptic patients who consecutively attended at Cairo University Hospital during the period from January to November 2013 were subjected to PCR/RFLP in order to detect the point mutations at domain V of the H. pylori 23S rRNA associated with clarithromycin resistance. The PCR amplicon of the 23S H. pylori rRNA is restricted with MboII for detection of A2142G mutation and with BsaI for A2143G mutation.

RESULTS

The prevalence of H. pylori infection among 100 patients was 70%; clarithromycin resistance was detected in 39/70 (57.7%) of positive H. pylori isolates. Occurrence of 23S rRNA A2142G mutations resulted in two DNA fragments (418 and 350 bp) by PCR-RFLP; on the other hand, no A2143G mutations were detected.

CONCLUSIONS

The high prevalence of clarithromycin resistance (57.7%) caused by A2142G mutations at domain V of the H. pylori 23S rRNA may mandate changing of the standard clarithromycin-containing triple therapy. The PCR/RFLP assay was a rapid and accurate method for molecular detection of H. pylori infection in addition to determination of different nucleotide mutations causing clarithromycin resistance.

Low prevalence of clarithromycin-resistant Helicobacter pylori isolates with A2143G point mutation in the 23S rRNA gene in North India

Resistance of Helicobacter pylori to clarithromycin is associated with a single base substitution in the 23S rRNA gene. In this study, clarithromycin-resistant H. pylori isolates were analysed for the presence of 23S rRNA gene mutations. H. pylori were isolated from 68 patients suffering from various gastroduodenal diseases in North India. Minimum inhibitory concentrations (MICs) were determined by the agar dilution method, and point mutations in clarithromycin-resistant strains were identified by PCR-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing. Clarithromycin resistance was observed in 11.8% (8/68) of the H. pylori isolates in North India. The A2143G point mutation in the 23S rRNA gene was found in 87.5% (7/8) of the clarithromycin-resistant strains, and the A2142G mutation in association with the T2182C mutation was found in 12.5% (1/8). In conclusion, the continued high prevalence of clarithromycin-sensitive H. pylori strains (88.2%) observed in this study allows the use of the triple-therapy regimen for the treatment of H. pylori infection in this region. Surveillance studies need to be conducted at regular intervals for clarithromycin resistance in the population. To our knowledge, this is the first study in India to report that point mutations at position A2143G and at A2142G in association with T2182C are associated with clarithromycin resistance, confirming reports from other parts of the world.

Detection of 23SrRNA Mutations Strongly Related to Clarithromycin Resistance in Helicobacter pylori Strains Isolated From Patients in the North of Iran

Background:

Helicobacter pylori is curved Gram negative and microaerophilic bacilli that have infected half of the world’s population. It is recognized as the causative agent of duodenal ulcer, gastritis peptic ulcer, mucosa-associated lymphoid tissue (MALT) lymphoma and is associated with gastric adenocarcinoma. Resistance to clarithromycin is related to point mutations in 23SrRNA gene on nt 2143 and 2144, when A turns to G, and A2143G is the most important type. These mutations lead to reduced affinity of antibiotics to their ribosomal target and are considered as the main cause of treatment failure.

Objectives:

The aim of this study was to determine the frequency of A2143G point mutation in 23SrRNA of H.pylori strains isolated from gastric biopsies of patients in Rasht, north of Iran, by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Patients and Methods:

A descriptive study was performed on 89 H.pylori strains, which were isolated from gastric biopsies of patients with gastric disorders such as gastritis, peptic ulcer, duodenal ulcer, non-ulcer dyspepsia and gastric adenocarcinoma. Isolated strains were tested for clarithromycin resistance using as breakpoint a minimum inhibitory concentration (MIC) of ≥ 1 mg/L by the E-test. The presence of H.pylori DNA was confirmed by amplifying the ureC (glmM) gene by PCR. Also, point mutation on 23SrRNA gene (A2142G and A2143G) was detected by PCR-RFLP using MboII and BsaI restriction endonucleases in all extracted DNA.

Results:

Of the 89 H.pylori isolates, eighty-four were susceptible to clarithromycin, while five (5.6%) were resistant. All DNA samples of resistant strains, which were treated with BsaI had A2143G mutation. There was no point mutation in the sensitive strains of H. pylori. Also, we detected no mutation on nt A2142G of resistant strains.

Conclusions:

In the present study, the frequency of clarithromycin resistance was lower than the other studies conducted in Iran. Resistance frequency in samples isolated from gastric ulcer was higher than other gastric disorders. Women and patients aged more than 60 years old showed the most resistance frequency in this study. All resistant strains had the A2143G genotype.

Detection of clarithromycin-resistant Helicobacter pylori in clinical specimens by molecular methods: A review

Various molecular methods have been developed to rapidly detect clarithromycin (CLR) resistance in Helicobacter pylori isolates in clinical specimens. All of these assays for detecting CLR resistance in H. pylori are based on detection of mutations in the 23S rRNA gene. In this article, we summarise current knowledge regarding the detection of H. pylori CLR resistance in clinical specimens by molecular tests. The available data showed that restriction fragment length polymorphism (RFLP), 3'-mismatch PCR, DNA sequencing, the PCR line probe assay (PCR-LiPA) and fluorescence in situ hybridisation assay (FISH) are able to detect CLR-resistant H. pylori in clinical specimens with excellent specificity and sensitivity. However, several factors limit their clinical application, including fastidious, time-consuming preparation and low-throughput as well as carrying a risk of contamination. Furthermore, as an invasive method, FISH is not suitable for children or the elderly. Among the molecular methods, one that is most promising for the future is real-time PCR probe hybridisation technology using fluorescence resonance energy transfer (FRET) probes, which can rapidly detect CLR resistance with high sensitivity and specificity in biopsies and stool specimens, even though mixed infections are present in clinical specimens. Moreover, due to the advantages that this method is simple, rapid and economical, real-time PCR is technically feasible for clinical application in small- and medium-sized hospitals in developing countries. Second, with high sensitivity, specificity and throughput, DNA chips will also be a valuable tool for detecting resistant H. pylori isolates from cultures and clinical specimens.

Low efficacy of levofloxacin-doxycycline-based third-line triple therapy for Helicobacter pylori eradication in Italy

AIM: To evaluate a levofloxacin-doxycycline-based triple therapy with or without a susceptibility culture test in non-responders to Helicobacter pylori (H. pylori) eradication.

METHODS: A total of 142 (99 women, 43 men; mean 53.0 ± 12.7 years) non-responders to more than two H. pylori eradication therapies underwent susceptibility culture tests or were treated with a seven-day triple therapy consisting of esomeprazole, 20 mg b.i.d., levofloxacin, 500 mg b.i.d., and doxycycline, 100 mg b.i.d., randomly associated with (n = 71) or without (n = 71) Lactobacillus casei DG. H. pylori status was checked in all patients at enrollment and at least 8 wk after the end of therapy. Compliance and tolerability of regimens were also assessed.

RESULTS: H. pylori eradication was achieved in < 50% of patients [per prototol (PP) = 49%; intention to treat (ITT) = 46%]. Eradication rate was higher in patients administered probiotics than in those without (PP = 55% vs 43%; ITT = 54% vs 40%). Estimated primary resistance to levofloxacin was 18% and multiple resistance was 31%. Therapy was well tolerated, and side effects were generally mild, with only one patient experiencing severe effects.

CONCLUSION: Third-line levofloxacin-doxycycline triple therapy had a low H. pylori eradication efficacy, though the success and tolerability of this treatment may be enhanced with probiotics.

Improved allele-specific PCR assays for detection of clarithromycin and fluoroquinolone resistant of Helicobacter pylori in gastric biopsies: identification of N87I mutation in GyrA

Molecular testing can rapidly detect Helicobacter pylori susceptibility using gastric biopsies. Allele-specific polymerase chain reaction (ASP-PCR) was used to identify H. pylori 23S rRNA and gyrA mutation using gastric biopsies from Colombian patients and confirmed by PCR and sequencing of the 23S rRNA and gyrA genes. The sensitivity and specificity of ASP-PCR were compared with susceptibilities measured by agar dilution. Samples included gastric biopsies from 107 biopsies with H. pylori infections and 20 H. pylori negative. The sensitivity and specificity of ASP-PCR for the 23S rRNA gene were both 100%. The sensitivity and specificity of ASP-PCR for the gyrA gene, published in 2007 by Nishizawa et al., were 52% and 92.7%, respectively; the lower sensitivity was due to the presence of mutation N87I in our samples, which were not detected by the test. In this study, we designed new primers to detect the mutation N87I in GyrA. The ASP-PCR was performed with the original primers plus the new primers. The molecular test with the new primers improved the sensitivity to 100%. In conclusion, ASP-PCR provides a specific and rapid means of predicting resistance to clarithromycin and levofloxacin in gastric biopsies.

Clarithromycin-based standard triple therapy can still be effective for Helicobacter pylori eradication in some parts of the Korea

We evaluated the antibiotic resistance rates and eradication rates of clarithromycin based triple therapy from 2005 to 2010 retrospectively. In addition, we investigated the mechanism of clarithromycin resistance in Helicobacter pylori strains isolated from Korean patients. Two hundred and twelve strains of H. pylori were isolated from 204 patients. H. pylori ATCC 43504 was used as the standard strain. The eradication rates of H. pylori from 2005 to 2010 were 89.3%, 82.6%, 86.3%, 87.7%, 81.8%, and 84.2%, respectively. Total eradication rate was 84.9%. DNA sequences of the 23S RNA gene in clarithromycin-resistant strains were determined. The resistance rates of H. pylori to amoxicillin, clarithromycin, metronidazole, tetracycline, ciprofloxacin, moxifloxacin, and levofloxacin were 9.0%, 8.5%, 36.3%, 0%, 14.2%, 14.2%, and 14.2%, respectively. The multidrug resistance rate of H. pylori was 16.5%. Sequence analysis of clarithromycin-resistant strains showed an A2144G mutation in 8 of 14 strains (57.1%), a T2183C mutation in 5 of 14 strains (35.7%), and double mutations of both A2144G and T2183C in 1 of 14 strains (7.1%). In the present study, triple therapy may still be an effective eradication therapy for H. pylori infections in Korea. The A2144G and T2183C mutations are mainly present in clarithromycin-resistant isolates.

The study of mutation in 23S rRNA resistance gene of Helicobacter pylori to clarithromycin in patients with gastrointestinal disorders in Isfahan - Iran

Background:

Helicobacter pylori antimicrobial resistance is an important factor responsible for treatment failure. The purpose of this study was evaluating the prevalence of point mutations in clarithromycin-resistant clinical isolates of H. pylori in Isfahan city of Iran.

Materials and Methods:

Thirty isolates of H. pylori from 130 biopsy specimens were isolated by culture and confirmed by biochemical and PCR tests. The MIC of clarithromycin antibiotic for 30 clinical isolates of H. pylori was determined by E-test method. The point mutations in the 288 bp of 23S rRNA gene of H. pylori were investigated in four clarithromycin-resistant clinical isolates by PCR followed by sequencing.

Results:

Among 30 isolates of H. pylori, 4 cases were resistant to clarithromycin. One point mutation was found at position T2243C in the 23S rRNA gene in all resistance isolates.

Conclusions:

In our study, H. pylori resistance to clarithromycin associated with point mutation at position 2243 (T2243C).

Low Helicobacter pylori primary resistance to clarithromycin in gastric biopsy specimens from dyspeptic patients of a city in the interior of São Paulo, Brazil

BACKGROUND

Clarithromycin, amoxicillin, and a pump proton inhibitor are the most common drugs recommended as first-line triple therapy for H.pylori treatment, which results in eradication rates close to 80%, varying regionally, principally due to emergency cases and increases of clarithromycin resistant strains. Nucleotide substitutions at the H. pylori domain V of the 23S rRNA fraction are involved in the macrolide resistance and the A2142G and A2143G mutations are predominant in clinical isolates worldwide including in Brazil. As H. pylori culture is fastidious, we investigated the primary occurrence of H. pylori A2142G and A2143G rDNA 23S mutations using a molecular approach directly on gastric biopsies of dyspeptic patients consecutively attended at Hospital das Clinicas of Marilia, São Paulo, Brazil.

METHODS

Biopsy specimens obtained from 1137 dyspeptic patients, were subjected to histopathology and H. pylori diagnosis by histology and PCR. PCR/RFLP assay was used to detect A2142G and A2143G point mutations at domain V of the H. pylori 23S rDNA associated with clarithromycin resistance. Through the developed assay, a 768 bp PCR amplicon corresponding to1728 to 2495 bp of the 23S H. pylori rDNA is restricted with MboII for A2142G mutation detection and with BsaI for A2143G mutation detection. Occurrence of 23S rDNA A2142G results in two DNA fragments (418 and 350 bp) and of 23S rDNA A2143G results in three DNA fragments (108, 310 and 350pb), due to a conserved BsaI restriction site.

RESULTS

The PCR method used to diagnose H. pylori presented sensitivity, specificity and accuracy of 77,6%, 79,3% and 78,6%, respectively, compared to histology, the gold standard method for H. pylori diagnosis used in our routine. Prevalence of H.pylori with clarithromycin resistant genotypes was 2,46%, with predominance of A2143G 23S rDNA point mutation.

CONCLUSIONS

The PCR/RFLP assay was a rapid and accurate H.pylori diagnostic and clarithromycin resistance determination method useful for routine practice. As prevalence of primary resistance of H.pylori to clarithromycin due to A2142G and A2143G mutations remains low in Marilia, the standard clarithromycin containing triple therapy is still valid.

Application of real-time PCR stool assay for Helicobacter pylori detection and clarithromycin susceptibility testing in Brazilian children

BACKGROUND

Helicobacter pylori ClariRes assay is a novel commercially available real-time PCR assay allowing H. pylori detection and clarithromycin susceptibility testing in either gastric biopsy or stool specimens.

OBJECTIVE

The aim of this study was to validate the novel biprobe real-time assay in stool specimens from 217 dyspeptic children.

METHODS

DNA from gastric biopsies and stool specimens were obtained and submitted to the biprobe real time assay for H. pylori detection and clarithromycin susceptibility testing.

RESULTS

The sensitivity, specificity, and test accuracy were 69, 100 and 93.9% for the detection of H. pylori infection and 83.3, 100 and 95.6%, for detection of clarithromycin resistance.

CONCLUSION

This assay proved to be appropriate for H. pylori clarithromycin susceptibility testing, particularly in children populations where a high prevalence of clarithromycin-resistant strains is suspected.

Mechanisms of Helicobacter pylori antibiotic resistance: An updated appraisal

Helicobacter pylori (H. pylori) antibiotic resistance is the main factor affecting the efficacy of the current eradicating therapies. The aim of this editorial is to report on the recent information about the mechanisms accounting for the resistance to the different antibiotics currently utilized in H. pylori eradicating treatments. Different mechanisms of resistance to clarithromycin, metronidazole, quinolones, amoxicillin and tetracycline are accurately detailed (point mutations, redox intracellular potential, pump efflux systems, membrane permeability) on the basis of the most recent data available from the literature. The next hope for the future is that by improving the knowledge of resistance mechanisms, the elaboration of rational and efficacious associations for the treatment of the infection will be possible. Another auspicious progress might be the possibility of a cheap, feasible and reliable laboratory test to predict the outcome of a therapeutic scheme.

Optimal therapy for Helicobacter pylori infections

Although Helicobacter pylori infection is both a common and a serious bacterial infection, antimicrobial therapies have rarely been optimized, are prescribed empirically, and provide inferior results compared with antimicrobial therapies for other common infectious diseases. The effectiveness of many of the frequently recommended H. pylori infection treatment regimens has been increasingly compromised by antimicrobial resistance. Regional data on the susceptibility of strains of H. pylori to available antimicrobials are sorely needed. Noninvasive molecular methods are possible to assess clarithromycin susceptibility in isolates obtained from stool specimens. As a general rule, clinicians should prescribe therapeutic regimens that have a ≥90% or, preferably, ≥95% eradication rate locally. If no available regimen can achieve a ≥90% eradication rate, clinicians should use the most effective regimen(s) available locally. Eradication of infection should always be confirmed after treatment in order to provide feedback regarding local effectiveness and an early warning of increasing resistance. In most regions of the world, four-drug treatment regimens, including a PPI plus three antimicrobials (clarithromycin, metronidazole/tinidazole and amoxicillin), or a PPI plus a bismuth plus tetracycline and metronidazole provide the best results. Standard triple therapy (a PPI, amoxicillin and clarithromycin) should now be avoided owing to increasing resistance to this treatment.

Characterization of clarithromycin resistance in isolates of Helicobacter pylori from the UAE

BACKGROUND

Clarithromycin therapy is effective in eradicating Helicobacter pylori. However, the resistance of H. pylori to clarithromycin is increasingly reported. The present study aimed to characterize the types of mutations present in the 23S rRNA genes of isolates of clarithromycin-resistant H. pylori from the UAE.

METHODS

Clarithromycin susceptibility of H. pylori isolates (n = 26) was determined by E tests. Analyses for point mutations in domain V of the 23S rRNA genes in clarithromycin-resistant and-sensitive strains were performed by sequence analysis of amplified PCR products.

RESULTS

Out of 100 gastric antral biopsy samples, 26 were positive for H. pylori by culture, and 29 were positive by PCR. Of the 26 culture isolates, five (19.2%) were resistant to clarithromycin and 24 were sensitive. The MIC of the resistant strains ranged from 3 to 24 microg/mL (median 24). All of the clarithromycin-resistant isolates had point mutations in the 23S rRNA gene. Two isolates had an A2142G 23S rRNA mutation, and three had A2143G mutations.

CONCLUSION

Clarithromycin resistance was common in this small collection of H. pylori isolates from the UAE. The A2142G and A2143G mutations were associated with clarithromycin resistance.

High level of antimicrobial resistance in French Helicobacter pylori isolates

BACKGROUND

Helicobacter pylori is a human pathogen responsible for serious diseases including peptic ulcer disease and gastric cancer. The recommended triple therapy included clarithromycin but increasing resistance has undermined its effectiveness. It is therefore important to be aware of the local prevalence of antimicrobial resistance to adjust treatment strategy.

MATERIALS AND METHODS

Overall, 530 biopsies were collected between 2004 and 2007. The antimicrobial susceptibility of H. pylori was determined by E-test and molecular methods.

RESULTS

Among these, 138/530 (26%) strains were resistant to clarithromycin, 324/530 (61%) to metronidazole and 70/530 (13.2%) to ciprofloxacin. Whereas no resistance against amoxicillin and tetracycline was observed, only one strain was resistant to rifampicin. Compared to the patients never treated for H. pylori infection, the prevalence of resistance was significantly higher in patients previously treated (19.1% vs 68% for clarithromycin; 13.2% vs 53.3% for both clarithromycin and metronidazole). The trend analysis revealed an increase of primary resistance to ciprofloxacin between 2004 and 2005 (7.3%) vs 2006-2007 (14.1%) (p = .04) and the secondary resistance reached 22.7% in 2007. Interestingly, 27 biopsies (19.6%) contained a double population of clarithromycin-susceptible and -resistant strains.

CONCLUSIONS

The reported high prevalence of clarithromycin and multiple resistances of H. pylori suggest that the empiric therapy with clarithromycin should be abandoned as no longer pretreatment susceptibility testing has assessed the susceptibility of the strain. As culture and antibiogram are not routinely performable in most clinical laboratories, the use of molecular test should be developed to allow a wide availability of pretreatment susceptibility testing.

Characterization of clarithromycin resistance in Malaysian isolates of Helicobacter pylori

AIM: To characterize the types of mutations present in the 23S rRNA genes of Malaysian isolates of clarithromycin-resistant Helicobacter pylori (H pylori).

METHODS: Clarithromycin susceptibility of H pylori isolates was determined by E test. Analyses for point mutations in the domain V of 23S rRNA genes in clarithromycin-resistant and -sensitive strains were performed by sequence analysis of amplified polymerase chain reaction products. Restriction fragment length polymorphism was performed using BsaI and MboII enzymes to detect restriction sites that correspond to the mutations in the clarithromycin-resistant strains.

RESULTS: Of 187 isolates from 120 patients, four were resistant to clarithromycin, while 183 were sensitive. The MIC of the resistant strains ranged from 1.5 to 24 &mgr;g/mL. Two isolates had an A2142G mutation and another two had A2143G mutations. A T2182C mutation was detected in two out of four clarithromycin-resistant isolates and in 13 of 14 clarithromycin-sensitive isolates. Restriction enzyme analyses with BsaI and MboII were able to detect the mutations.

CONCLUSION: Clarithromycin resistance is an uncommon occurrence among Malaysian isolates of H pylori strains and the mutations A2142G and A2143G detected were associated with low-level resistance.

Who's Winning the War? Molecular Mechanisms of Antibiotic Resistance in Helicobacter pylori

The ability of clinicians to wage an effective war against many bacterial infections is increasingly being hampered by skyrocketing rates of antibiotic resistance. Indeed, antibiotic resistance is a significant problem for treatment of diseases caused by virtually all known infectious bacteria. The gastric pathogen Helicobacter pylori is no exception to this rule. With more than 50% of the world's population infected, H. pylori exacts a tremendous medical burden and represents an interesting paradigm for cancer development; it is the only bacterium that is currently recognized as a carcinogen. It is now firmly established that H. pylori infection is associated with diseases such as gastritis, peptic and duodenal ulceration and two forms of gastric cancer, gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. With such a large percentage of the population infected, increasing rates of antibiotic resistance are particularly vexing for a treatment regime that is already fairly complicated; treatment consists of two antibiotics and a proton pump inhibitor. To date, resistance has been found to all primary and secondary lines of antibiotic treatment as well as to drugs used for rescue therapy.

Quadruplex real-time PCR assay using allele-specific scorpion primers for detection of mutations conferring clarithromycin resistance to Helicobacter pylori

We developed a single-vessel multiplex real-time PCR assay that detects Helicobacter pylori infection and identified the four existing alleles of the 23S rRNA genes of H. pylori--the wild-type sequence and the three mutations conferring clarithromycin resistance--using allele-specific Scorpion primers directly on biopsy specimens. The Scorpion primers combine a primer and a probe in a single molecule and are able to distinguish single-nucleotide polymorphism. Fluorescent signals, produced when the probes are annealed, are read in four channels by a SmartCycler thermocycler. The assay was first applied successfully on 4 reference and 61 clinical strains. MICs of clarithromycin were determined by the Etest method. A perfect concordance was obtained between Etest and Scorpion PCR. Mixed populations were better detected by Scorpion PCR. We examined 259 biopsies from 229 patients by culture, PCR-restriction fragment length polymorphism (RFLP), and Scorpion PCR. One biopsy, positive for culture, exhibited inhibitors for both PCR-RFLP and Scorpion PCR. Twelve biopsies were positive for PCR-RFLP and Scorpion PCR but negative for culture with concordant determination of mutations in the 23S rRNA genes by the two PCR assays. Three biopsies were positive for Scorpion PCR only. Compared to culture, the sensitivity of Scorpion PCR was 98.3% and the specificity was 92.5%. The Scorpion PCR assay provides a highly accurate, rapid, and precise method for the detection and determination of mutations conferring clarithromycin resistance to H. pylori.

Detection of the drug-resistant gene of Helicobacter pylori

Antibiotic-resistant Helicobacter pylori (H. pylori) and the resistance rate are increased due to the wide use of antibiotics. At present, the detection of antibiotic-resistant H. pylori is focused on the clarithromycin and metronidazole resistance testing using PCR-based molecular biology techniques. However, PCR-restriction fragment length polymorphism and real-time PCR in combination with melting curve analysis techniques have a broad prospect in detecting drug-resistant clarithromycin. They can detect it from tissue biopsy and stool samples, and thus can be used in detecting the resistance of a wide range of antibiotics. Western blot and PCR- restriction fragment length polymorphism can also detect the resistance of metronidazole, and can therefore develop into the routine procedures for detecting drug-resistant H. pylori.

Application of polymerase chain reaction-based assays for rapid identification and antibiotic resistance screening of Helicobacter pylori in gastric biopsies

The benefits of using a multiplex detection polymerase chain reaction (PCR) assay for Helicobacter pylori speciation and 2 real-time probe hybridization assays determining clarithromycin and tetracycline susceptibilities in gastric biopsies from 171 dyspeptic patients were investigated. Overall, 70 of 71 H. pylori culture-positive biopsies were PCR positive. For the 100 culture-negative biopsies, PCR identified a further 29 H. pylori positives (17% overall) and presence of resistance markers for clarithromycin (20/28) and tetracycline (2/28). The results demonstrated that PCR testing was valuable in providing improved detection rates and antibiotic susceptibility information when H. pylori culture was unsuccessful.

Modified allele-specific primer-polymerase chain reaction method for analysis of susceptibility of Helicobacter pylori strains to clarithromycin

BACKGROUND AND AIM

Most clarithromycin-resistant strains of Helicobacter pylori have a mutation from adenine (A) to guanine (G) at position 2142 or 2143 of the 23S rRNA gene. Our aim in this study was to develop a polymerase chain reaction (PCR)-based assay that could determine these mutations in a single reaction tube.

METHODS

We designed the forward primer FP2143G and the reverse primer RP2142G, which specifically anneal with the 2143G- and 2142G-mutated sequences, respectively, of the 23S rRNA gene of H. pylori. We also designed the forward primer FP-1 and reverse primer RP-1 upstream and downstream from the positions 2142 and 2143, respectively, to distinguish the wild-type A2142G and A2143G mutations from each other by amplicon sizes. DNA was extracted from 292 gastric tissue samples positive for rapid urease test, and the DNA underwent the PCR reaction. The results were compared with minimum inhibitory concentrations (MIC) for clarithromycin.

RESULTS

Helicobacter pylori strains with A2142G, A2143G and wild type could be distinguished by amplicon sizes by a single PCR reaction. The genotyping results were correlated well with the MIC values for clarithromycin. The median MIC for clarithromycin of the wild-type strains was <0.015 microg/mL. Those of strains with 2142G or 2143G were > or =1.0 microg/mL.

CONCLUSION

Our new PCR-based assay for 23S rRNA mutations of H. pylori is a useful method for detecting clarithromycin-resistant strains of H. pylori easily.

Detection of mixed clarithromycin-resistant and -susceptible Helicobacter pylori using nested PCR and direct sequencing of DNA extracted from faeces

The major cause of chemotherapy failure in patients with chronic gastritis and peptic ulcers caused by Helicobacter pylori is clarithromycin (CAM) resistance due to a mutation in the 23S rRNA gene. This study describes a non-invasive and accurate method for the detection of mixed CAM-resistant and -susceptible H. pylori by sequencing of the H. pylori 23S rRNA gene. Faeces were crushed with beads and the 23S rRNA gene was amplified using a nested PCR on the extracted DNA. Mutation analysis of this gene using this method showed that 20.4 % of patients carried mixed CAM-susceptible (wild type) and -resistant (A2142G or A2143G mutant) H. pylori. Furthermore, it was found that 66.6 % of patients who had been treated unsuccessfully carried one of these mutations in the 23S rRNA gene (including the mixed type), whilst standard culture detected CAM-resistant isolates in only 22.2 % of patients with unsuccessful treatment. These data suggest that, for successful therapy, the diagnosis method described here would more accurately detect CAM-resistant H. pylori, including mixed infections.

Rapid screening of clarithromycin resistance in Helicobacter pylori by pyrosequencing

Helicobacter pylori infections can be effectively treated with clarithromycin, a macrolide, in combination with other antibiotics, such as amoxicillin, tetracycline or metronidazole. The failure of H. pylori eradication is mainly associated with macrolide-resistant strains. Three point mutations (A2142G/C, A2143G, T2182C) in the peptidyltransferase region of domain V of the 23S rRNA have been described as being associated with clarithromycin resistance. Therefore, the determination of clarithromycin resistance by pyrosequencing was evaluated. H. pylori from 81 gastric biopsies was cultured and clarithromycin resistance was determined by Etest, as well as by pyrosequencing technology (PSQ 96 system; Biotage). The respective mutations were set in relation to the MIC measured in μg ml−1 by Etest. In this study, point mutations in positions 2142 and 2143 were associated with clarithromycin resistance. Mutations in position 2182 did not contribute to clarithromycin resistance. In addition, from 22 out of the 81 biopsies, clarithromycin resistance was determined directly without culturing H. pylori to save additional time. Identical results were obtained as compared to resistance testing with pure H. pylori strains. All results obtained by pyrosequencing were evaluated by Sanger sequencing. The data show that pyrosequencing to detect point mutation is a fast and reliable method for determining clarithromycin resistance in H. pylori, and provides the same results as the Etest.

Progress in research into the molecular mechanism of drug resistance of Helicobacter pylori

Helicobacter pylori is a pathogen of chronic and active gastritis. It is the main cause of chronic gastritis and peptic ulcer disease, and is directly related to diseases of the stomach and duodenum. This pathogen can also induce gastric carcinoma. With the extensive use of antibiotics, the number of drug resistant strains of H. pylori has rapidly increased. As a result, there are some difficulties in applying clinical therapy for diseases related to H. pylori. This paper aimed to first analyze the status and prevalence of antibiotic resistance, and then to review various drugs such as macrolides, imidazoles, tetracyclines, β-lactams and quinolones for systematically treating H. pylori infection. The mechanisms of various drug resistances, as well as detection and identification assays for typing drug resistance, are discussed. This paper presents accumulated clinical data and evidence for the clinical diagnosis and treatment of diseases related to H. pylori.

One-week versus two-week furazolidone-based quadruple therapy as the first-line treatment for Helicobacter pylori infection in Iran

BACKGROUND AND AIM

Furazolidone-based regimens for the eradication of Helicobacter pylori are low cost and effective although less tolerable. Our aim was to compare the efficacy and compliance of 1-week furazolidone-based quadruple therapy (furazolidone, amoxicillin, bismuth subcitrate, omeprazole; FABO) with 2-week quadruple therapy using the same drugs.

METHODS

One hundred and fifty-six consecutive patients with H. pylori related diseases were enrolled in our study. The patients were randomized into two groups of FABO1 and FABO2 groups receiving, 1 or 2 weeks' quadruple H. pylori eradication therapies, respectively, as follows: furazolidone (200 mg twice daily), amoxicillin (1 g twice daily), bismuth (240 mg twice daily) and omeprazole (20 mg twice daily). The chi(2) test was used to compare the efficacy of the therapies.

RESULTS

The per-protocol eradication rate in FABO1 and FABO2 groups were 56/66 (84.8%) and 57/69 (82.6%), respectively. The intention-to-treat eradication rate was 56/78 (71.8%) in FABO1 group and 57/78 (73.1%) in FABO2 group. There was not any significant statistical difference between two groups. A significant decrease in compliance in FABO2 group was seen.

CONCLUSION

This is an encouraging report showing a therapy with possible success in decreasing the duration of H. pylori infection as well as reaching the eradication rate of 80%.

Determination of mutations of the 23S rRNA gene of Helicobacter pylori by allele specific primer-polymerase chain reaction method

BACKGROUND AND AIMS

Susceptibility to clarithromycin of Helicobacter pylori (H. pylori) is caused by single nucleotide polymorphisms (SNPs) of the 23SrRNA gene. Allele specific primer-polymerase chain reaction (ASP-PCR) is one of the methods for determining SNPs, which can measure SNPs easily within a short period by PCR amplification alone without digestion with restriction enzymes. The aim of the present study was to develop the ASP-PCR assay for determining SNPs at positions 2,142 and 2,143 of the 23S rRNA gene of H. pylori.

METHODS

In total, 112 patients with H. pylori infection based on positive results of a rapid urease test (RUT) were enrolled in the study. Thirty-five had failed to eradicate H. pylori by a clarithromycin-based regimen. DNA was extracted from the RUT-positive gastric tissue samples. SNPs from adenine to guanine at positions 2,142 and 2,143 of the 23S rRNA of H. pylori (A2,142G and A2,143G) were determined by the ASP-PCR method. Minimum inhibitory concentrations (MICs) of clarithromycin for H. pylori were also measured.

RESULTS

Forty-nine of 112 patients were infected with wild-type strains of H. pylori. Thirty-nine patients were infected with strains with A2,143G mutations. Twenty-three patients were infected with both wild-type strains and those with A2,143G mutations. Only one patient was infected with the strain with A2,142G mutation. H. pylori strains with A2,143G or A2,142G mutation had significantly higher MICs for clarithromycin.

CONCLUSION

The ASP-PCR assay for 23S rRNA mutation of H. pylori is a useful method to detect clarithromycin-resistant strains of H. pylori easily.

Mutations in the 23S rRNA gene of clarithromycin-resistant Helicobacter pylori from Japan

The 23S rRNA gene in clinical isolates of Helicobacter pylori isolated between 1995 and 2004 from Japan was investigated and the relationship between mutations in this gene and clarithromycin susceptibility was studied. Among nine mutations that have previously been reported to confer clarithromycin resistance, an adenine-->guanine transition at position 2142 (A2142G) or 2143 (A2143G) was detected in all clarithromycin-resistant strains (n=67) but not in any clarithromycin-susceptible strains (n=17). Mutations at positions 2182, 2223, 2244 and 2288 have previously been reported to confer clarithromycin resistance in H. pylori isolates from Bangladesh, China and Brazil. However, these mutations were not associated with clarithromycin resistance in H. pylori isolates from Japan in this study. Other mutations at positions 2115, 2144 and 2711, which have also been reported to confer clarithromycin resistance in H. pylori from Sweden and Italy, were not detected in the strains in this study. Our results suggest that susceptibility to clarithromycin is predicted by detection of mutations at positions 2142 and 2143 of the 23S rRNA gene in H. pylori isolates in Japan.

Diagnosis of Helicobacter pylori: invasive and non-invasive tests

Helicobacter pylori infection can be diagnosed by invasive techniques requiring endoscopy and biopsy (e.g. histological examination, culture and rapid urease test) and by non-invasive techniques, such as serology, the urea breath test, urine/blood or detection of H. pylori antigen in stool specimen. Some non-invasive tests, such as the urea breath test and the stool antigen test, detect active infection: these are called 'active tests'. Non-invasive tests (e.g. serology, urine, near-patient tests) are markers of exposure to H. pylori but do not indicate if active infection is ongoing; these are 'passive tests'. Non-invasive test-and-treat strategies are widely recommended in the primary care setting. The choice of appropriate test depends on the pre-test probability of infection, the characteristics of the test being used and its cost-effectiveness.

Clarithromycin resistance in Helicobacter pylori strains isolated from French children: prevalence of the different mutations and coexistence of clones harboring two different mutations in the same biopsy

BACKGROUND

The aim of our study was to assess the different mutations involved in clarithromycin-resistant Helicobacter pylori strains isolated from French children and their temporal trends.

METHODS

The point mutations of H. pylori were detected by PCR followed by RFLP technique in 50 clarithromycin-resistant strains collected between 1993 and 2004 in France.

RESULTS

Clarithromycin resistance was observed in 23% (50/217) of H. pylori isolates. Two mutations A2143G and A2142G in the 23S rRNA genes of H. pylori were detected. The former was found in 45/50 (90%) of isolates. The rate of resistance increased with time from 18.6% in the period 1993-1996 to 41.6% in 2001-2004. No significant difference was observed in the distribution of mutations during the same periods. No correlation was found between any mutation and age, sex, and ethnic origin of children. Furthermore, no significant differences in minimal inhibitory concentrations level were observed according to the different point mutations. In all cases, only one point mutation was present, except in two cases where two different mutations were found in two different clones from the same biopsy.

CONCLUSION

The mutation A2143G is predominant in clarithromycin-resistant H. pylori strains isolated from children in France. We report for the first time the presence of two clarithromycin-resistant clones harboring two different mutations of the 23S rRNA genes present in the same biopsy specimen and genotypically identical as demonstrated by RAPD fingerprinting.

Helicobacter pylori and antimicrobial resistance: molecular mechanisms and clinical implications

Helicobacter pylori is an important human pathogen that colonises the stomach of about half of the world's population. The bacterium has now been accepted as the causative agent of several gastroduodenal disorders, ranging from chronic active gastritis and peptic ulcer disease to gastric cancer. The recognition of H pylori as a gastric pathogen has had a substantial effect on gastroenterological practice, since many untreatable gastroduodenal disorders with uncertain cause became curable infectious diseases. Treatment of H pylori infection results in ulcer healing and can reduce the risk of gastric cancer development. Although H pylori is susceptible to many antibiotics in vitro, only a few antibiotics can be used in vivo to cure the infection. The frequent indication for anti-H pylori therapy, together with the limited choice of antibiotics, has resulted in the development of antibiotic resistance in H pylori, which substantially impairs the treatment of H pylori-associated disorders. Antimicrobial resistance in H pylori is widespread, and although the prevalence of antimicrobial resistance shows regional variation per antibiotic, it can be as high as 95%. We focus on the treatment of H pylori infection and on the clinical relevance, mechanisms, and diagnosis of antimicrobial resistance.

Helicobacter pylori isolated from patients who later failed H. pylori eradication triple therapy readily develop resistance to clarithromycin

In this study, the ease of selection of clarithromycin resistance was investigated in clarithromycin-susceptible Helicobacter pylori strains isolated from patients with H. pylori infection prior to the administration of triple-combination eradication therapy (clarithromycin plus amoxicillin plus a proton pump inhibitor). Clarithromycin-susceptible strains isolated from ten patients in whom the eradication therapy was successful and from six patients in whom the eradication therapy was unsuccessful were exposed serially to subinhibitory concentrations of clarithromycin. The number of transfers required for the MICs of the strains to increase by 8- and 32-fold were 6.6 and 7.2, respectively, in the successful eradication group, and as few as 2.4 and 1.5, respectively, in the unsuccessful eradication group. The number of transfers required for the A2142G or A2143G point mutation of the 23S rRNA gene to be detected in the strains were 5 and 8, respectively, for the strains in the successful eradication group, and 1 and 2, respectively, for the strains in the unsuccessful eradication group. These results suggest that patients in the unsuccessful eradication group were infected with strains of H. pylori that readily became resistant to clarithromycin on exposure to the drug.

Rapid detection of clarithromycin resistance in Helicobacter pylori using a PCR-based denaturing HPLC assay

OBJECTIVES

We evaluated a new approach for the rapid detection of clarithromycin resistance in Helicobacter pylori, based on PCR and denaturing HPLC (DHPLC).

METHODS

A 180 bp fragment of the 23S rRNA gene was amplified using DNA from 81 clinical H. pylori isolates (51 isolates were shown to be resistant to clarithromycin by Etest), and, directly, from 101 gastric biopsies from patients with digestive diseases, who were infected with H. pylori as assessed by a 13C-urea breath test, histology and/or culture. DHPLC was used to detect mutations in all the PCR products.

RESULTS

DHPLC profiles for the 30 susceptible isolates all showed homoduplex peaks; the resistant isolates consistently generated heteroduplex peaks that were easily distinguishable from the wild-type H. pylori reference strain. Sequencing revealed point mutations in all the resistant isolates. Overall, five different mutations were detected. Four of these mutations (A2142G, A2142C, A2143G and T2182C) are known to be associated with clarithromycin resistance; the remaining mutation (C2195T) has not been previously described. This novel single-base substitution was found in combination with the common mutation A2143G. Of the biopsies tested, 25 specimens generated heteroduplexes due to sequence alterations (mutation A2142G, A2142C or A2143G). In one of these specimens, A2143G was found together with the novel mutation T2221C; in another, a mixture of wild-type and mutant (A2143G) sequences was detected. For 20 culture-positive out of the 25 biopsies DHPLC results confirmed the presence of clarithromycin resistance.

CONCLUSIONS

Our results suggest that the PCR-DHPLC assay is a valid tool for rapid assessment of clarithromycin resistance in H. pylori and that in the future it could be used directly on biopsy specimens, avoiding the need for culture-based methods.

Macrolide resistance in Campylobacter jejuni and Campylobacter coli: molecular mechanism and stability of the resistance phenotype

A collection of 23 macrolide-resistant Campylobacter isolates from different geographic areas was investigated to determine the mechanism and stability of macrolide resistance. The isolates were identified as Campylobacter jejuni or Campylobacter coli based on the results of the hippurate biochemical test in addition to five PCR-based genotypic methods. Three point mutations at two positions within the peptidyl transferase region in domain V of the 23S rRNA gene were identified. About 78% of the resistant isolates exhibited an A-->G transition at Escherichia coli equivalent base 2059 of the 23S rRNA gene. The isolates possessing this mutation showed a wide range of erythromycin and clarithromycin MICs. Thus, this mutation may incur a greater probability of treatment failure in populations infected by resistant Campylobacter isolates. Another macrolide-associated mutation (A-->C transversion), at E. coli equivalent base 2058, was detected in about 13% of the isolates. An A-->G transition at a position cognate with E. coli 23S rRNA base 2058, which is homologous to the A2142G mutation commonly described in Helicobacter pylori, was also identified in one of the C. jejuni isolates examined. In the majority of C. jejuni isolates, the mutations in the 23S rRNA gene were homozygous except in two cases where the mutation was found in two of the three copies of the target gene. Natural transformation demonstrated the transfer of the macrolide resistance phenotype from a resistant Campylobacter isolate to a susceptible Campylobacter isolate. Growth rates of the resulting transformants containing A-2058-->C or A-2059-->G mutations were similar to that of the parental isolate. The erythromycin resistance of six of seven representative isolates was found to be stable after successive subculturing in the absence of erythromycin selection pressure regardless of the resistance level, the position of the mutation, or the number of the mutated copies of the target gene. One C. jejuni isolate showing an A-2058-->G mutation, however, reverted to erythromycin and clarithromycin susceptibility after 55 subcultures on erythromycin-free medium. Investigation of ribosomal proteins L4 and L22 by sequence analysis in five representative isolates of C. jejuni and C. coli demonstrated no significant macrolide resistance-associated alterations in either the L4 or the L22 protein that might explain either macrolide resistance or enhancement of the resistance level.

Development of a highly sensitive method for detection of clarithromycin-resistant Helicobacter pylori from human feces

Gastric infection of clarithromycin (CAM)-resistant Helicobacter pylori is one of the major causes of failure to eradicate this organism. A noninvasive and useful method for the detection of CAM-resistant H. pylori from human feces by restriction fragment length polymorphism (RFLP)-nested polymerase chain reaction (PCR) targeting the mutation of the 23S rRNA gene that confers CAM-resistance in H. pylori was developed in this study. Our nested PCR method detected DNA of H. pylori in feces with high sensitivity and specificity compared with both an enzyme-linked immunoadsorbent assay (ELISA) of H. pylori in feces and the isolation of H. pylori from gastric biopsy. Furthermore, the results of mutation analysis of the H. pylori 23S rRNA gene amplified from feces completely correlated with both that of the H. pylori 23S rRNA gene amplified from the isolates of gastric biopsy and the susceptibility of H. pylori isolates to CAM. Therefore, our results show that this RFLP/nested PCR method is useful for the accurate diagnosis of CAM-resistant H. pylori infection from feces.