Search for novel candidate mutations for metronidazole resistance in Helicobacter pylori using next-generation sequencing. Antimicrob Agents Chemother. 2015;59:2343-2348. [PMID: 25645832 DOI: 10.1128/aac.04852-14]

Functional determination of site-mutations in rdxA involved in metronidazole resistance of Helicobacter pylori

Background

Metronidazole (MTZ) is among the first-line drugs against the human gastric pathogen Helicobacter pylori (H. pylori). MTZ is used as a prodrug that is activated by an oxygen-insensitive enzyme NADPH nitroreductase (RdxA). Loss-of-function mutations in rdxA make H. pylori MTZ resistant; however, experimental proof is lacking.

Methods

We collected 139 gastric biopsy samples from patients suspected of H. pylori infection in Shanghai, and amplified Hp-specific rdxA gene from 134 samples. All these rdxA genes were sequenced and phylogenetically compared. The effect of mutations on RdxA function was measured by expressing them in Escherichia coli DH5α by using the MTZ sensitivity test.

Results

In total, 134 gastric biopsy samples were identified as H. pylori positive. Of the 134 samples, 74 and 6 had point mutations at the various sites or promoter region of rdxA, generating truncated and extended fused proteins, respectively. The remaining 54 were full-length with single nucleotide variation (SNV) compared with the wild-type RdxA from H. pylori, with 49 clustering with hpEastAsia, 3 with hpEurope, and 2 with hpNEAfrica. All 134 rdxA were expressed in E. coli DH5α; 22 and 112 resultant strains showed MTZ-sensitive and MTZ-resistant phenotypes, respectively. Comparative analysis of single nucleotide polymorphisms (SNPs) in the functional and inactivated RdxA revealed 14 novel mutations in RdxA, 5 of which conferred MTZ resistance: S18F, D59S, L62I, S79N, and A187V.

Conclusion

The occurrence of MTZ resistance induced by site-mutation of RdxA in patients with H. pylori infection was 83.6% (112/134) in the Shanghai region. The major form of loss-of-function mutation was truncation of RdxA translation at a rate of 58/112 (51.8%). Molecular detection reliably determined the resistance of H. pylori to MTZ. Thus, the functional mutants involved in MTZ resistance facilitate clinical diagnosis and medication based on sequence analysis.

Antibiotic Resistance of Helicobacter pylori: Mechanisms and Clinical Implications

Helicobacter pylori is a pathogenic bacterium associated with various gastrointestinal diseases, including chronic gastritis, peptic ulcers, mucosa-associated lymphoid tissue lymphoma, and gastric cancer. The increasing rates of H. pylori antibiotic resistance and the emergence of multidrug-resistant strains pose significant challenges to its treatment. This comprehensive review explores the mechanisms underlying the resistance of H. pylori to commonly used antibiotics and the clinical implications of antibiotic resistance. Additionally, potential strategies for overcoming antibiotic resistance are discussed. These approaches aim to improve the treatment outcomes of H. pylori infections while minimizing the development of antibiotic resistance. The continuous evolution of treatment perspectives and ongoing research in this field are crucial for effectively combating this challenging infection.

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

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

Whole Genome Sequencing for Studying Helicobacter pylori Antimicrobial Resistance

Antibiotic resistance (AMR) is an alarming concern worldwide and Helicobacter pylori, one of the most prevalent bacteria, is not an exception. With antibiotics being its primary therapy, increasing resistance leads to a higher rate of treatment failure. Understanding the genomic mechanisms of resistance to clarithromycin, levofloxacin, metronidazole, amoxicillin, tetracycline, and rifampicin through next-generation sequencing-based molecular tools, such as whole genome sequencing (WGS), can be of great value, not only to direct a patient's treatment, but also to establish and optimize treatment guidelines according to the local epidemiology and to avoid the use of inappropriate antibiotics. WGS approaches allow us to gain insight into the genomic determinants involved in AMR. To this end, different pipelines and platforms are continuously being developed. In this study, we take a more detailed view of the use and progression of WGS for in-depth study of H. pylori's AMR.

Prevalence of antibiotic resistance of Helicobacter pylori isolates in Shanghai, China

OBJECTIVE

This study aimed to evaluate the resistance of Helicobacter pylori (H. pylori) to common antibiotics in Shanghai.

METHODS

A total of 1171 eligible subjects participated in the study. Antibiotic susceptibility to six common antibiotics was examined with the disk diffusion method. Mutations in resistant-related genes were identified via Sanger sequencing analysis.

RESULTS

Overall, the resistance rates of strains to amoxicillin, clarithromycin, levofloxacin, metronidazole, tetracycline, and furazolidone were 0.1%, 27.8%, 31.1%, 79.9%, 0.1%, and 0.5%, respectively. Compared with untreated patients, resistance rates of clarithromycin (P < 0.01), levofloxacin (P < 0.01), and metronidazole were significantly higher in re-treated patients (P < 0.05). The total multiple resistance rate was 40.5%. Age (levofloxacin), gender (clarithromycin, levofloxacin, and metronidazole) and endoscopic findings (clarithromycin and levofloxacin) were independent factors influencing antibiotic resistance. High correlation was observed between the drug susceptibility test and molecular test for the resistance to clarithromycin and levofloxacin.

CONCLUSIONS

The resistance rates of H. pylori to amoxicillin, tetracycline, and furazolidone were low, whereas the resistance rates of H. pylori to clarithromycin, levofloxacin, and metronidazole were high, especially in re-treated patients. Our results indicate that the clinical resistance patterns of clarithromycin and levofloxacin could be guided by relevant gene mutations.

Helicobacter pylori Infection, Its Laboratory Diagnosis, and Antimicrobial Resistance: a Perspective of Clinical Relevance

Despite the recent decrease in overall prevalence of Helicobacter pylori infection, morbidity and mortality rates associated with gastric cancer remain high. The antimicrobial resistance developments and treatment failure are fueling the global burden of H. pylori-associated gastric complications. Accurate diagnosis remains the opening move for treatment and eradication of infections caused by microorganisms. Although several reports have been published on diagnostic approaches for H. pylori infection, most lack the data regarding diagnosis from a clinical perspective. Therefore, we provide an intensive, comprehensive, and updated description of the currently available diagnostic methods that can help clinicians, infection diagnosis professionals, and H. pylori researchers working on infection epidemiology to broaden their understanding and to select appropriate diagnostic methods. We also emphasize appropriate diagnostic approaches based on clinical settings (either clinical diagnosis or mass screening), patient factors (either age or other predisposing factors), and clinical factors (either upper gastrointestinal bleeding or partial gastrectomy) and appropriate methods to be considered for evaluating eradication efficacy. Furthermore, to cope with the increasing trend of antimicrobial resistance, a better understanding of its emergence and current diagnostic approaches for resistance detection remain inevitable.

A Survey of Helicobacter pylori Antibiotic-Resistant Genotypes and Strain Lineages by Whole-Genome Sequencing in China

Antibiotic resistance is the most important factor leading to failed Helicobacter pylori eradication therapy, and personalized treatment based on antibiotic susceptibility is becoming increasingly important. To strengthen the understanding of antibiotic genotypic resistance of H. pylori and identify new antibiotic resistance loci, in this study, we identified phenotypic resistance information for 60 clinical isolates and compared the concordance of phenotypic and genotypic resistance using whole-genome sequencing (WGS). Clarithromycin and levofloxacin genotypic resistance was in almost perfect concordance with phenotypic resistance, with kappa coefficients of 0.867 and 0.833, respectively. All strains with the R16H/C mutation and truncation in rdxA were metronidazole resistant, with 100% specificity. For other genes of concern, at least one phenotypically sensitive strain had a previous mutation related to antibiotic resistance. Moreover, we found that the A1378G mutation of HP0399 and the A149G mutation of FabH might contribute to tetracycline resistance and multidrug resistance, respectively. Overall, the inference of resistance to clarithromycin and levofloxacin from genotypic resistance is reliable, and WGS has been very helpful in discovering novel H. pylori resistance loci. In addition, WGS has also enhanced our study of strain lineages, providing new ways to understand resistance information and mechanisms.

Biomarker Characterization and Prediction of Virulence and Antibiotic Resistance from Helicobacter pylori Next Generation Sequencing Data

The Gram-negative bacterium Helicobacter pylori colonizes c.a. 50% of human stomachs worldwide and is the major risk factor for gastric adenocarcinoma. Its high genetic variability makes it difficult to identify biomarkers of early stages of infection that can reliably predict its outcome. Moreover, the increasing antibiotic resistance found in H. pylori defies therapy, constituting a major human health problem. Here, we review H. pylori virulence factors and genes involved in antibiotic resistance, as well as the technologies currently used for their detection. Furthermore, we show that next generation sequencing may lead to faster characterization of virulence factors and prediction of the antibiotic resistance profile, thus contributing to personalized treatment and management of H. pylori-associated infections. With this new approach, more and permanent data will be generated at a lower cost, opening the future to new applications for H. pylori biomarker identification and antibiotic resistance prediction.

Correlation Analysis Among Genotype Resistance, Phenotype Resistance, and Eradication Effect After Resistance-Guided Quadruple Therapies in Refractory Helicobacter pylori Infections

Objectives

The antimicrobial resistance of Helicobacter pylori (H. pylori) in most countries and regions has increased significantly. It has not been fully confirmed whether the detection of H. pylori resistance gene mutation can replace antibiotic drug sensitivity test to guide the clinical personalized treatment. The objective of this study was to assess and compare the efficacy of different antimicrobial resistance-guided quadruple therapies in refractory H. pylori-infected individuals who had undergone unsuccessful prior eradication treatments.

Methods

From January 2019 to February 2020, genotypic and phenotypic resistances were determined by polymerase chain reaction (PCR), whole genome sequencing (WGS) and broth microdilution test, respectively, in 39 H. pylori-infected patients who have failed eradication for at least twice. The patients were retreated with bismuth quadruple therapy for 14 days according to individual antibiotic resistance results. Eradication status was determined by the ¹³C-urea breath test.

Results

The overall eradication rate was 79.5% (31/39, 95% CI 64.2–89.5%) in the intention-to-treat (ITT) analysis and 88.6% (31/35, 95% CI 73.5–96.1%) in the per- protocol analysis (PP) analysis. The presence of amoxicillin resistance (OR, 15.60; 95% CI, 1.34–182.09; p = 0.028), female sex (OR, 12.50; 95% CI, 1.10–142.31; p = 0.042) and no less than 3 prior eradication treatments (OR, 20.25; 95% CI, 1.67–245.44; p = 0.018), but not the methods for guiding therapy (p > 0.05) were associated with treatment failure. Resistance-guided therapy achieved eradication rates of more than 80% in these patients. The eradication rate of H. pylori in the phenotypic resistance-guided group was correlated well with genotype resistance-guided groups, including PCR and WGS.

Conclusion

Culture or molecular method guiding therapy can enable personalized, promise salvage treatments, and achieve comparably high eradication rates in patients with refractory H. pylori infection. The detection of H. pylori resistance mutations has a good clinical application prospect.

Protocol Study Register

[clinicaltrials.gov], identifier [ChiCTR1800020009].

Automated extraction of genes associated with antibiotic resistance from the biomedical literature

The detection of bacterial antibiotic resistance phenotypes is important when carrying out clinical decisions for patient treatment. Conventional phenotypic testing involves culturing bacteria which requires a significant amount of time and work. Whole-genome sequencing is emerging as a fast alternative to resistance prediction, by considering the presence/absence of certain genes. A lot of research has focused on determining which bacterial genes cause antibiotic resistance and efforts are being made to consolidate these facts in knowledge bases (KBs). KBs are usually manually curated by domain experts to be of the highest quality. However, this limits the pace at which new facts are added. Automated relation extraction of gene-antibiotic resistance relations from the biomedical literature is one solution that can simplify the curation process. This paper reports on the development of a text mining pipeline that takes in English biomedical abstracts and outputs genes that are predicted to cause resistance to antibiotics. To test the generalisability of this pipeline it was then applied to predict genes associated with Helicobacter pylori antibiotic resistance, that are not present in common antibiotic resistance KBs or publications studying H. pylori. These genes would be candidates for further lab-based antibiotic research and inclusion in these KBs. For relation extraction, state-of-the-art deep learning models were used. These models were trained on a newly developed silver corpus which was generated by distant supervision of abstracts using the facts obtained from KBs. The top performing model was superior to a co-occurrence model, achieving a recall of 95%, a precision of 60% and F1-score of 74% on a manually annotated holdout dataset. To our knowledge, this project was the first attempt at developing a complete text mining pipeline that incorporates deep learning models to extract gene-antibiotic resistance relations from the literature. Additional related data can be found at https://github.com/AndreBrincat/Gene-Antibiotic-Resistance-Relation-Extraction

Helicobacter pylori infection and antibiotic resistance - from biology to clinical implications

Helicobacter pylori is a major human pathogen for which increasing antibiotic resistance constitutes a serious threat to human health. Molecular mechanisms underlying this resistance have been intensively studied and are discussed in this Review. Three profiles of resistance - single drug resistance, multidrug resistance and heteroresistance - seem to occur, probably with overlapping fundamental mechanisms and clinical implications. The mechanisms that have been most studied are related to mutational changes encoded chromosomally and disrupt the cellular activity of antibiotics through target-mediated mechanisms. Other biological attributes driving drug resistance in H. pylori have been less explored and this could imply more complex physiological changes (such as impaired regulation of drug uptake and/or efflux, or biofilm and coccoid formation) that remain largely elusive. Resistance-related attributes deployed by the pathogen cause treatment failures, diagnostic difficulties and ambiguity in clinical interpretation of therapeutic outcomes. Subsequent to the increasing antibiotic resistance, a substantial drop in H. pylori treatment efficacy has been noted globally. In the absence of an efficient vaccine, enhanced efforts are needed for setting new treatment strategies and for a better understanding of the emergence and spread of drug-resistant bacteria, as well as for improving diagnostic tools that can help optimize current antimicrobial regimens.

Next Generation Sequencing for the Prediction of the Antibiotic Resistance in Helicobacter pylori: A Literature Review

Background and aims: Only a few antimicrobials are effective against H. pylori, and antibiotic resistance is an increasing problem for eradication therapies. In 2017, the World Health Organization categorized clarithromycin resistant H. pylori as a "high-priority" bacterium. Standard antimicrobial susceptibility testing can be used to prescribe appropriate therapies but is currently recommended only after the second therapeutic failure. H. pylori is, in fact, a "fastidious" microorganism; culture methods are time-consuming and technically challenging. The advent of molecular biology techniques has enabled the identification of molecular mechanisms underlying the observed phenotypic resistance to antibiotics in H. pylori. The aim of this literature review is to summarize the results of original articles published in the last ten years, regarding the use of Next Generation Sequencing, in particular of the whole genome, to predict the antibiotic resistance in H. pylori.Methods: a literature research was made on PubMed. The research was focused on II and III generation sequencing of the whole H. pylori genome. Results: Next Generation Sequencing enabled the detection of novel, rare and complex resistance mechanisms. The prediction of resistance to clarithromycin, levofloxacin and amoxicillin is accurate; for other antimicrobials, such as metronidazole, rifabutin and tetracycline, potential genetic determinants of the resistant status need further investigation.

Prediction of Streptococcus uberis clinical mastitis treatment success in dairy herds by means of mass spectrometry and machine-learning

Streptococcus uberis is one of the leading pathogens causing mastitis worldwide. Identification of S. uberis strains that fail to respond to treatment with antibiotics is essential for better decision making and treatment selection. We demonstrate that the combination of supervised machine learning and matrix-assisted laser desorption ionization/time of flight (MALDI-TOF) mass spectrometry can discriminate strains of S. uberis causing clinical mastitis that are likely to be responsive or unresponsive to treatment. Diagnostics prediction systems trained on 90 individuals from 26 different farms achieved up to 86.2% and 71.5% in terms of accuracy and Cohen’s kappa. The performance was further increased by adding metadata (parity, somatic cell count of previous lactation and count of positive mastitis cases) to encoded MALDI-TOF spectra, which increased accuracy and Cohen’s kappa to 92.2% and 84.1% respectively. A computational framework integrating protein–protein networks and structural protein information to the machine learning results unveiled the molecular determinants underlying the responsive and unresponsive phenotypes.

Whole-Genome Sequencing and Comparative Genomics of Three Helicobacter pylori Strains Isolated from the Stomach of a Patient with Adenocarcinoma

Helicobacter pylori is a common pathogen associated with several severe digestive diseases. Although multiple virulence factors have been described, it is still unclear the role of virulence factors on H. pylori pathogenesis and disease progression. Whole genome sequencing could help to find genetic markers of virulence strains. In this work, we analyzed three complete genomes from isolates obtained at the same point in time from a stomach of a patient with adenocarcinoma, using multiple available bioinformatics tools. The genome analysis of the strains B508A-S1, B508A-T2A and B508A-T4 revealed that they were cagA, babA and sabB/hopO negative. The differences among the three genomes were mainly related to outer membrane proteins, methylases, restriction modification systems and flagellar biosynthesis proteins. The strain B508A-T2A was the only one presenting the genotype vacA s1, and had the most distinct genome as it exhibited fewer shared genes, higher number of unique genes, and more polymorphisms were found in this genome. With all the accumulated information, no significant differences were found among the isolates regarding virulence and origin of the isolates. Nevertheless, some B508A-T2A genome characteristics could be linked to the pathogenicity of H. pylori.

Molecular testing for H. pylori clarithromycin and quinolone resistance: a prospective Chinese study

In China, there is a high prevalence of antibiotic-resistant Helicobacter pylori infections in the population. The aim of the study was to assess a new ARMS-PCR test for detection of H. pylori clarithromycin resistance (CR) and quinolone resistance (QR) mutations and evaluate the spectrum of antibiotic resistance in patients from three Chinese provinces. Sanger sequencing and multiplex ARMS-PCR were used to detect H. pylori CR and QR bacteria in gastric biopsy samples. Among the 1,182 patients enrolled with gastritis, 643 (54.4%) were positive for H. pylori. Of these, 371 (57.7%) had antibiotic-resistant strains, comprising 236 (63.6%) with a single drug antibiotic-resistant strain and 135 (36.4%) with multiple drug-resistant strains. Following Sanger sequencing analysis of 23S rRNA and gyrA gene for mutations (antibiotic resistance markers), rates of CR, QR, and multidrug resistance (CR and QR) were 19.9, 12.0, and 25.8%, respectively. The 23S rRNA CR mutation A2143G (286, 96.9%) and the gyrA QR mutations C261A (85, 31.5%) and G271A (71, 26.3%) were common. Benchmarking against Sanger sequencing results, multiplex ARMS-PCR test had a high diagnostic sensitivity and specificity for detection of CR (96 and 93%), QR (95 and 92%) and multidrug resistance (95 and 95%). Based on our findings, the high incidence of single and multiple antibiotic resistance requires the routine checking of antibiotic resistance in all patients with suspected H. pylori infections. Multiplex ARMS-PCR is a simple and rapid test that can be now used for more efficient treatment of H. pylori infections and reduces the misuse of antibiotics.

A comparative whole genome analysis of Helicobacter pylori from a human dense South Asian setting

Helicobacter pylori, a Gram-negative bacterium, is associated with a wide range of gastric diseases such as gastritis, duodenal ulcer, and gastric cancer. The prevalence of H pylori and risk of disease vary in different parts of the world based on the prevailing bacterial lineage. Here, we present a contextual and comparative genomics analysis of 20 clinical isolates of H pylori from patients in Bangladesh. Despite a uniform host ethnicity (Bengali), isolates were classified as being part of the HpAsia2 (50%) or HpEurope (50%) population. Out of twenty isolates, eighteen isolates were cagA positive, with two HpEurope isolates being cagA negative, three EPIYA motif patterns (AB, AB-C, and ABC-C) were observed among the cagA-positive isolates. Three vacA genotypes were observed with the s1m1i1dic1 genotype observed in 75% of isolates; the s1m2i1d1c2 and s2m2i2d2c2 genotypes were found to be 15% and 10% of isolates, respectively. The non-virulent genotypes s2m2i2d2c2 was only observed in HpEurope population isolates. Genotypic analysis of oipA gene, present in all isolates, revealed five different patterns of the CT repeat; all HpAsia2 isolates were in "ON" while 20% of HpEurope isolates were genotypically "OFF." The three blood group antigen binding adhesins encoded genes (bab genes) examined and we observed that the most common genotype was (babA/babB/-) found in eight isolates, notably six were HpAsia2 isolates. The babA gene was found in all HpAsia2 isolates but present in only half of the HpEurope isolates. In silico antibiotic susceptibility analysis revealed that 40% of the strains were multi-drug resistant. Mutations associated with resistance to metronidazole, fluoroquinolone, and clarithromycin were detected 90%, 45%, and 5%, respectively, in H pylori strain. In conclusion, it is evident that two populations of H pylori with similar antibiotic profiles are predominant in Bangladesh, and it appears that genotypically the HpAisa2 isolates are potentially more virulent than the HpEurope isolates.

Phenotypic and Genotypic Analysis of Resistant Helicobacter pylori Strains Isolated from Children with Gastrointestinal Diseases

Antibiotic resistance of Helicobacter pylori is currently a global issue. The aim of this study was to analyze actual antibiotic resistance rates of H. pylori strains isolated from children with primary infections and to compare the incidence of mutations that determine resistance to clarithromycin (CH) and metronidazole (MET) in children with different clinical diagnoses. A total of 91 H. pylori strains were isolated from 108 children with primary infections. Drug susceptibility testing of the strains was performed using E-test method. Classical sequencing of DNA fragments was used to detect point mutations for CH and MET resistance. Resistance to CH was detected in 31% of isolated strains (28/91), while resistance to MET and CH was detected in 35% (32/91) of strains. A2143G was the most frequently detected mutation and was dominant among strains isolated from children with peptic ulcer disease (80%). Mutations in the rdxA gene were found significantly more frequently among MET-resistant strains than MET-sensitive strains (p = 0.03, Chi2 = 4.3909). In children, a higher frequency of H. pylori multiresistant strains was observed compared with the previous study in the same area. Differences were found in the occurrence of point mutations among H. pylori strains resistant to CH isolated from children with different clinical diagnoses.

Genotype profiles of Helicobacter pylori from gastric biopsies and strains with antimicrobial-induced resistance

BACKGROUND AND AIMS

The genotypic method could significantly shorten the time needed to obtain antibiotic susceptibility data for Helicobacter pylori. The aim of this study was to explore the profile of H. pylori from gastric biopsies and strains with antibiotic-induced resistance.

METHODS

A total of 124 gastric biopsies were used to perform gene sequencing and to perform bacterial culture and susceptibility testing. Seven susceptible strains were selected to develop resistance to clarithromycin, levofloxacin, and metronidazole. Four susceptible strains were selected to transfer candidate mutations. The genotype profiles of these groups were analyzed by sequencing analysis. The antibiotic susceptibility of these strains was detected using the E-test method.

RESULTS

Phenotypic resistance to clarithromycin, levofloxacin, and metronidazole was observed in 35.5%, 40.0%, and 79.8% strains, respectively. Point mutations in 23 S rRNA, gyrA, and rdxA genes were observed in 39.5%, 38.7%, and 86.3% of gastric biopsies, respectively. The A2143G mutation in the 23S rRNA occurs in most clarithromycin-resistant samples. The A2142C point mutation showed a higher efficacy than A2142G and A2143G for inducing clarithromycin resistance. The D91N and N87K mutations in gyrA occurs in most levofloxacin-resistant samples, and double point mutations showed a higher efficacy than single mutations for inducing levofloxacin resistance. Phenotypic resistance and mutations in rdxA lacked consistency.

CONCLUSION

Genotype-based gastric biopsy analysis was reliable for determining clarithromycin and levofloxacin resistance. A2143G in 23S rRNA and N87K/D91N in the gyrA gene occurred in most resistant strains. Mutations in the rdxA gene were not good indicators of metronidazole resistance.

Review of current diagnostic methods and advances in Helicobacter pylori diagnostics in the era of next generation sequencing

Helicobacter pylori (H. pylori) infection is highly prevalent in the human population and may lead to severe gastrointestinal pathology including gastric and duodenal ulcers, mucosa associated tissue lymphoma and gastric adenocarcinoma. In recent years, an alarming increase in antimicrobial resistance and subsequently failing empiric H. pylori eradication therapies have been noted worldwide, also in many European countries. Therefore, rapid and accurate determination of H. pylori’s antibiotic susceptibility prior to the administration of eradication regimens becomes ever more important. Traditionally, detection of H. pylori and its antimicrobial resistance is done by culture and phenotypic drug susceptibility testing that are cumbersome with a long turn-around-time. Recent advances in diagnostics provide new tools, like real-time polymerase chain reaction (PCR) and line probe assays, to diagnose H. pylori infection and antimicrobial resistance to certain antibiotics, directly from clinical specimens. Moreover, high-throughput whole genome sequencing technologies allow the rapid analysis of the pathogen’s genome, thereby allowing identification of resistance mutations and associated antibiotic resistance. In the first part of this review, we will give an overview on currently available diagnostic methods for detection of H. pylori and its drug resistance and their implementation in H. pylori management. The second part of the review focusses on the use of next generation sequencing technology in H. pylori research. To this end, we conducted a literature search for original research articles in English using the terms “Helicobacter”, “transcriptomic”, “transcriptome”, “next generation sequencing” and “whole genome sequencing”. This review is aimed to bridge the gap between current diagnostic practice (histology, rapid urease test, H. pylori culture, PCR and line probe assays) and new sequencing technologies and their potential implementation in diagnostic laboratory settings in order to complement the currently recommended H. pylori management guidelines and subsequently improve public health.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Study of rdxA and frxA genes mutations in metronidazole-resistant and -susceptible Helicobacter pylori clinical isolates from the central region of Portugal

OBJECTIVES

Helicobacter pylori is one of the most prevalent global pathogens colonising an estimated 50% of the world's population. Although metronidazole (MTZ) is an important antibiotic playing a relevant role in various H. pylori eradication therapies, its frequent consumption results in an increased frequency of resistance with a consequent negative impact on treatment efficacy. Mutations on genes encoding NADPH nitroreductases, commonly known as rdxA gene (oxygen-insensitive) and frxA gene (flavinreductase) have been associated to H. pylori resistance to metrodinazole. The aim of this study was to evaluate the mutation profile of rdxA and frxA genes in a population of 38 H. pylori isolates with phenotypic patterns of susceptibility and resistance to this antibiotic.

METHODS

Touchdown PCR with the purpose of amplifying rdxA and frxA genes in one PCR was used. Sequence data were made by pair-wise sequence alignment and were examined in terms of codons, and comparison was achieved regarding amino acids.

RESULTS

Although repeated mutations occurred in positions 118, 131, 172 and 183 of rdxA and in positions 72, 73, 110, 126 and 193 of frxA, it must be highlighted that the mutations are widespread along these two genes in this population. Furthermore, six MTZ-resistant isolates did not present any mutation in the frxA gene.

CONCLUSIONS

This work appears to confirm that mutations in rdxA and frxA alone are unable to explain MTZ resistance in H. pylori isolates and therefore additional mechanisms may exist and should be investigated.

Genetic Determinants and Prediction of Antibiotic Resistance Phenotypes in Helicobacter pylori

Helicobacter pylori is a major human pathogen. Diagnosis of H. pylori infection and determination of its antibiotic susceptibility still mainly rely on culture and phenotypic drug susceptibility testing (DST) that is time-consuming and laborious. Whole genome sequencing (WGS) has recently emerged in medical microbiology as a diagnostic tool for reliable drug resistance prediction in bacterial pathogens. The aim of this study was to compare phenotypic DST results with the predictions based on the presence of genetic determinants identified in the H. pylori genome using WGS. Phenotypic resistance to clarithromycin, metronidazole, tetracycline, levofloxacin, and rifampicin was determined in 140 clinical H. pylori isolates by E-Test^®, and the occurrence of certain single nucleotide polymorphisms (SNPs) in target genes was determined by WGS. Overall, there was a high congruence of >99% between phenotypic DST results for clarithromycin, levofloxacin, and rifampicin and SNPs identified in the 23S rRNA, gyrA, and rpoB gene. However, it was not possible to infer a resistance phenotype for metronidazole based on the occurrence of distinct SNPs in frxA and rdxA. All 140 H. pylori isolates analysed in this study were susceptible to tetracycline, which was in accordance with the absence of double or triple nucleotide substitutions in the 16S rRNA gene.

A GWAS on Helicobacter pylori strains points to genetic variants associated with gastric cancer risk

Background

Helicobacter pylori are stomach-dwelling bacteria that are present in about 50% of the global population. Infection is asymptomatic in most cases, but it has been associated with gastritis, gastric ulcers and gastric cancer. Epidemiological evidence shows that progression to cancer depends upon the host and pathogen factors, but questions remain about why cancer phenotypes develop in a minority of infected people. Here, we use comparative genomics approaches to understand how genetic variation amongst bacterial strains influences disease progression.

Results

We performed a genome-wide association study (GWAS) on 173 H. pylori isolates from the European population (hpEurope) with known disease aetiology, including 49 from individuals with gastric cancer. We identified SNPs and genes that differed in frequency between isolates from patients with gastric cancer and those with gastritis. The gastric cancer phenotype was associated with the presence of babA and genes in the cag pathogenicity island, one of the major virulence determinants of H. pylori, as well as non-synonymous variations in several less well-studied genes. We devised a simple risk score based on the risk level of associated elements present, which has the potential to identify strains that are likely to cause cancer but will require refinement and validation.

Conclusion

There are a number of challenges to applying GWAS to bacterial infections, including the difficulty of obtaining matched controls, multiple strain colonization and the possibility that causative strains may not be present when disease is detected. Our results demonstrate that bacterial factors have a sufficiently strong influence on disease progression that even a small-scale GWAS can identify them. Therefore, H. pylori GWAS can elucidate mechanistic pathways to disease and guide clinical treatment options, including for asymptomatic carriers.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0550-3) contains supplementary material, which is available to authorized users.

Anti-proliferation effect of blue light-emitting diodes against antibiotic-resistant Helicobacter pylori

BACKGROUND AND AIM

Infection by Helicobacter pylori is implicated in a wide range of upper gastrointestinal diseases. Owing to the rapid emergence of antibiotic-resistant strains of H. pylori, the development of novel treatment modalities for antibiotic-resistant H. pylori infection is a key priority. Blue light-emitting diodes (LED) may represent a unique option owing to their antimicrobial effect. In this study, we aimed to evaluate the anti-proliferative effect of blue LED against antibiotic-resistant H. pylori.

METHODS

Ten antibiotic-resistant strains and one sensitive H. pylori strain were used in this study. After irradiation by blue LED along time course, the viability of H. pylori was evaluated by enumerating colony forming units. Morphological changes in H. pylori were observed using a scanning electron microscope. Reductase activity was measured as an indicator of bacterial cellular activity. Total reactive oxygen species was monitored using fluorescence intensity and fluorescence microscope imaging.

RESULTS

After irradiation by blue LED, the numbers of H. pylori in all the strains were significantly reduced compared with control group. The H. pylori exhibited a short rod-shaped morphology after irradiation; no such change was observed in H. pylori not exposed to blue LED. Re-irradiation of surviving strain after the initial irradiation also exhibited the same anti-proliferation effect. After blue LED irradiation, bacterial cellular activity was lower, and total reactive oxygen species production was significantly higher in blue LED group, compared with that in control.

CONCLUSIONS

Blue LED could be a new treatment to eradicate infection with antibiotic-resistant H. pylori.

Resistance mechanisms of Helicobacter pylori and its dual target precise therapy

Helicobacter pylori drug resistance presents a significant challenge to the successful eradication of this pathogen. To find strategies to improve the eradication efficacy of H. pylori, it is necessary to clarify the resistance mechanisms involved. The mechanisms of H. pylori drug resistance can be investigated from two angles: the pathogen and the host. A comprehensive understanding of the molecular mechanisms of H. pylori resistance based on both pathogen and host would aid the implementation of precise therapy, or ideally "dual target precise therapy" (bacteria and host-specific target therapy). In recent years, with increased understanding of the mechanisms of H. pylori resistance, the focus of eradication has shifted from disease-specific to patient-specific treatment. The implementation of "precision medicine" has also provided a new perspective on the treatment of infectious diseases. In this article, we systematically review current research on H. pylori drug resistance from the perspective of both the pathogen and the host. We also review therapeutic strategies targeted to pathogen and host factors that are aimed at achieving precise treatment of H. pylori.

A review on metronidazole: an old warhorse in antimicrobial chemotherapy

The 5-nitroimidazole drug metronidazole has remained the drug of choice in the treatment of anaerobic infections, parasitic as well as bacterial, ever since its development in 1959. In contrast to most other antimicrobials, it has a pleiotropic mode of action and reacts with a large number of molecules. Importantly, metronidazole, which is strictly speaking a prodrug, needs to be reduced at its nitro group in order to become toxic. Reduction of metronidazole, however, only takes place under very low concentrations of oxygen, explaining why metronidazole is exclusively toxic to microaerophilic and anaerobic microorganisms. In general, resistance rates amongst the pathogens treated with metronidazole have remained low until the present day. Nevertheless, metronidazole resistance does occur, and for the treatment of some pathogens, especially Helicobacter pylori, metronidazole has become almost useless in some parts of the world. This review will give an account on the current status of research on metronidazole's mode of action, metronidazole resistance in eukaryotes and prokaryotes, and on other 5-nitroimidazoles in use.

[Frequency of Helicobacter pylori nitroreductase RdxA mutations for metronidazole activation in a population in the Cauca Department, Colombia]

INTRODUCTION

Resistance to metronidazole is a key factor associated with Helicobacter pylori treatment failure. Even though resistance is mostly associated with RdxA nitroreductase mutations, studies of this H. pylori protein in Popayán (Colombia) are still incipient.

OBJECTIVE

To evaluate the frequency of mutations in the RdxA nitroreductase in a population of patients with H. pylori-positive gastrointestinal disease.

MATERIALS AND METHODS

We amplified the DNA of 170 gastric biopsies by PCR to detect mutations in the RdxA nitroreductase. An analysis of DNA sequences translated into amino acid sequences was done and then compared to the reference strain 26695.

RESULTS

The frequency of RdxA nitroreductase mutations in this study population was 78%. Its most frequent distribution was found in positions D59N (153 samples), R131K (101 samples), R90K (97 samples), A118T (42 samples), I160F (32 samples) and H97T (26 samples), and meaningful stop codons Q50*, D59*; E75*, C159* and I160* in five, one, three, ten and six samples, respectively. The most common virulence genotype was vacAs1/m1 cagA negative (48.6 %).

CONCLUSIONS

The high frequency of RdxA nitroreductase mutations in H. pylori isolates in Popayán (Colombia) indicates that empirical therapy with metronidazole may not be a valid option for the eradication of H. pylori in patients of the studied population.

Transcriptomics Indicates Active and Passive Metronidazole Resistance Mechanisms in Three Seminal Giardia Lines

Giardia duodenalis is an intestinal parasite that causes 200-300 million episodes of diarrhoea annually. Metronidazole (Mtz) is a front-line anti-giardial, but treatment failure is common and clinical resistance has been demonstrated. Mtz is thought to be activated within the parasite by oxidoreductase enzymes, and to kill by causing oxidative damage. In G. duodenalis, Mtz resistance involves active and passive mechanisms. Relatively low activity of iron-sulfur binding proteins, namely pyruvate:ferredoxin oxidoreductase (PFOR), ferredoxins, and nitroreductase-1, enable resistant cells to passively avoid Mtz activation. Additionally, low expression of oxygen-detoxification enzymes can allow passive (non-enzymatic) Mtz detoxification via futile redox cycling. In contrast, active resistance mechanisms include complete enzymatic detoxification of the pro-drug by nitroreductase-2 and enhanced repair of oxidized biomolecules via thioredoxin-dependent antioxidant enzymes. Molecular resistance mechanisms may be largely founded on reversible transcriptional changes, as some resistant lines revert to drug sensitivity during drug-free culture in vitro, or passage through the life cycle. To comprehensively characterize these changes, we undertook strand-specific RNA sequencing of three laboratory-derived Mtz-resistant lines, 106-2ID10, 713-M3, and WB-M3, and compared transcription relative to their susceptible parents. Common up-regulated genes encoded variant-specific surface proteins (VSPs), a high cysteine membrane protein, calcium and zinc channels, a Mad-2 cell cycle regulator and a putative fatty acid α-oxidase. Down-regulated genes included nitroreductase-1, putative chromate and quinone reductases, and numerous genes that act proximal to PFOR. Transcriptional changes in 106-2ID10 diverged from those in 713-r and WB-r (r ≤ 0.2), which were more similar to each other (r = 0.47). In 106-2ID10, a nonsense mutation in nitroreductase-1 transcripts could enhance passive resistance whereas increased transcription of nitroreductase-2, and a MATE transmembrane pump system, suggest active drug detoxification and efflux, respectively. By contrast, transcriptional changes in 713-M3 and WB-M3 indicated a higher oxidative stress load, attributed to Mtz- and oxygen-derived radicals, respectively. Quantitative comparisons of orthologous gene transcription between Mtz-resistant G. duodenalis and Trichomonas vaginalis, a closely related parasite, revealed changes in transcripts encoding peroxidases, heat shock proteins, and FMN-binding oxidoreductases, as prominent correlates of resistance. This work provides deep insight into Mtz-resistant G. duodenalis, and illuminates resistance-associated features across parasitic species.

Clarithromycin-Based Triple Therapy is Still Useful as an Initial Treatment for Helicobacter pylori Infection in the Dominican Republic

AbstractHelicobacter pylori antibiotic susceptibility in the Dominican Republic has not been monitored. We assessed H. pylori antibiotic susceptibility in the Dominican Republic, and analyzed H. pylori mutations associated with antibiotic resistance. We recruited 158 dyspeptic patients in Santo Domingo and used agar dilution to test susceptibility to five antibiotics. Polymerase chain reaction-based sequencing was used to assess gyrA, gyrB, rdxA, frxA, and 23S rRNA mutations; next-generation sequencing was used to identify other metronidazole resistance-associated genes. Among 64 H. pylori strains isolated, we identified two (3.1%), one (1.6%), and no strains with clarithromycin, amoxicillin, and tetracycline resistance, respectively. Moreover, high frequency of metronidazole resistance (53/64, 82.8%) was observed, whereas levofloxacin resistance is emerging (23/64, 35.9%). We identified many rdxA and frxA mutations in metronidazole-resistant strains, but no synergistic effect was apparent. We revealed novel mutations in dppA, dppB, fdxA, and fdxB, irrespective of rdxA and frxA mutations. Novel mutations at Ser-14 of trx1 and Arg-221 of dapF were associated with different levels of metronidazole resistance. Most levofloxacin-resistant strains had a substitution at Asn-87 of gyrA, including the strain with the highest levofloxacin resistance, whereas only three substitutions were found at Ser-479 of gyrB with no synergistic effect. Besides the 23S rRNA A2142G mutation, we observed another mutation at T1958G in both clarithromycin-resistant strains. We confirmed high metronidazole and levofloxacin resistance associated with genetic mutations in the Dominican Republic. However, prevalence of clarithromycin resistance was low, suggesting that standard clarithromycin-based triple therapy remains useful as initial treatment of H. pylori infection.

Molecular and Proteomic Analysis of Levofloxacin and Metronidazole Resistant Helicobacter pylori

Antibiotic resistance in bacteria incurs fitness cost, but compensatory mechanisms may ameliorate the cost and sustain the resistance even under antibiotics-free conditions. The aim of this study was to determine compensatory mechanisms of antibiotic resistance in H. pylori. Five strains of levofloxacin-sensitive H. pylori were induced in vitro to develop resistance. In addition, four pairs of metronidazole-sensitive and -resistant H. pylori strains were isolated from patients carrying dual H. pylori populations that consist of both sensitive and resistant phenotypes. Growth rate, virulence and biofilm-forming ability of the sensitive and resistant strains were compared to determine effects of compensatory response. Proteome profiles of paired sensitive and resistant strains were analyzed by liquid chromatography/mass spectrophotometry (LC/MS). Although there were no significant differences in growth rate between sensitive and resistant pairs, bacterial virulence (in terms of abilities to induce apoptosis and form biofilm) differs from pair to pair. These findings demonstrate the complex and strain-specific phenotypic changes in compensation for antibiotics resistance. Compensation for in vitro induced levofloxacin resistance involving mutations of gyrA and gyrB was functionally random. Furthermore, higher protein translation and non-functional protein degradation capabilities in naturally-occuring dual population metronidazole sensitive-resistant strains may be a possible alternative mechanism underlying resistance to metronidazole without mutations in rdxA and frxA. This may explain the lack of mutations in target genes in ~10% of metronidazole resistant strains.

Surveillance of Helicobacter pylori Antibiotic Susceptibility in Indonesia: Different Resistance Types among Regions and with Novel Genetic Mutations

Information regarding Helicobacter pylori antibiotic resistance in Indonesia was previously inadequate. We assessed antibiotic susceptibility for H. pylori in Indonesia, and determined the association between virulence genes or genetic mutations and antibiotic resistance. We recruited 849 dyspeptic patients who underwent endoscopy in 11 cities in Indonesia. E-test was used to determine the minimum inhibitory concentration of five antibiotics. PCR-based sequencing assessed mutations in 23S rRNA, rdxA, gyrA, gyrB, and virulence genes. Next generation sequencing was used to obtain full-length sequences of 23S rRNA, infB, and rpl22. We cultured 77 strains and identified 9.1% with clarithromycin resistance. Low prevalence was also found for amoxicillin and tetracycline resistance (5.2% and 2.6%, respectively). In contrast, high resistance rates to metronidazole (46.7%) and levofloxacin (31.2%) were demonstrated. Strains isolated from Sumatera Island had significantly higher metronidazole resistance than those from other locations. Metronidazole resistant strains had highly distributed rdxA amino acid substitutions and the 23S rRNA A2143G mutation was associated with clarithromycin resistance (42.9%). However, one strain with the highest MIC value had a novel mutation in rpl22 without an A2143G mutation. Mutation at Asn-87 and/or Asp-91 of gyrA was associated with levofloxacin-resistance and was related to gyrB mutations. In conclusions, although this is a pilot study for a larger survey, our current data show that Indonesian strains had the high prevalence of metronidazole and levofloxacin resistance with low prevalence of clarithromycin, amoxicillin, and tetracycline resistance. Nevertheless, clarithromycin- or metronidazole-based triple therapy should be administered with caution in some regions of Indonesia.

Emerging Helicobacter pylori levofloxacin resistance and novel genetic mutation in Nepal

Background

The prevalence of Helicobacter pylori antibiotic susceptibility in the Nepalese strains is untracked. We determined the antibiotic susceptibility for H. pylori and analyzed the presence of genetic mutations associated with antibiotic resistance in Nepalese strains.

Results

This study included 146 consecutive patients who underwent gastroduodenal endoscopy in Kathmandu, Nepal. Among 42 isolated H. pylori, there was no resistance to amoxicillin and tetracycline. In contrast, similar with typical South Asian patterns; metronidazole resistance rate in Nepalese strains were extremely high (88.1 %, 37/42). Clarithromycin resistance rate in Nepalese strains were modestly high (21.4 %, 9/42). Most of metronidazole resistant strains had highly distributed rdxA and frxA mutations, but were relative coincidence without a synergistic effect to increase the minimum inhibitory concentration (MIC). Among strains with the high MIC, 63.6 % (7/11) were associated with frameshift mutation at position 18 of frxA with or without rdxA involvement. However, based on next generation sequencing data we found that one strain with the highest MIC value had a novel mutation in the form of amino acid substituted at Ala-212, Gln-382, Ile-485 of dppA and Leu-145, Thr-168, Glu-117, Val-121, Arg-221 in dapF aside from missense mutations in full-length rdxA. Mutations at Asn-87 and/or Asp-91 of the gyrA were predominantly in levofloxacin-resistant strains. The gyrB mutation had steady relationship with the gyrA 87–91 mutations. Although three (44.4 %) and two (22.2 %) of clarithromycin resistant strains had point mutation on A2143G and A2146G, we confirmed the involvement of rpl22 and infB in high MIC strains without an 23SrRNA mutation.

Conclusions

The rates of resistance to clarithromycin, metronidazole and levofloxacin were high in Nepalese strains, indicating that these antibiotics-based triple therapies are not useful as first-line treatment in Nepal. Bismuth or non-bismuth-based quadruple regimens, furazolidone-based triple therapy or rifabutin-based triple therapy may become alternative strategy in Nepal.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0873-6) contains supplementary material, which is available to authorized users.

Human Lysozyme Synergistically Enhances Bactericidal Dynamics and Lowers the Resistant Mutant Prevention Concentration for Metronidazole to Helicobacter pylori by Increasing Cell Permeability

Metronidazole (MNZ) is an effective agent that has been employed to eradicate Helicobacter pylori (H. pylori). The emergence of broad MNZ resistance in H. pylori has affected the efficacy of this therapeutic agent. The concentration of MNZ, especially the mutant prevention concentration (MPC), plays an important role in selecting or enriching resistant mutants and regulating therapeutic effects. A strategy to reduce the MPC that can not only effectively treat H. pylori but also prevent resistance mutations is needed. H. pylori is highly resistant to lysozyme. Lysozyme possesses a hydrolytic bacterial cell wall peptidoglycan and a cationic dependent mode. These effects can increase the permeability of bacterial cells and promote antibiotic absorption into bacterial cells. In this study, human lysozyme (hLYS) was used to probe its effects on the integrity of the H. pylori outer and inner membranes using as fluorescent probe hydrophobic 1-N-phenyl-naphthylamine (NPN) and the release of aspartate aminotransferase. Further studies using a propidium iodide staining method assessed whether hLYS could increase cell permeability and promote cell absorption. Finally, we determined the effects of hLYS on the bactericidal dynamics and MPC of MNZ in H. pylori. Our findings indicate that hLYS could dramatically increase cell permeability, reduce the MPC of MNZ for H. pylori, and enhance its bactericidal dynamic activity, demonstrating that hLYS could reduce the probability of MNZ inducing resistance mutations.

Bacterial factors associated with Helicobacter pylori antibiotic resistance

Helicobacter pylori (H. pylori) infection is the most widespread chronic bacterial infection and is closely associated with many diseases. In recent years, however, H. pylori is becoming increasingly difficult to eradicate due to the growing antibiotic resistance. Among the reasons for the failed eradication, some factors of H. pylori itself play a main role. H. pylori can resist antibiotics by producing inactivating enzymes, changing the drug targets, preventing oxidation-reduction electron transfer, decreasing membrane permeability and activating efflux pump, changing bacterial metabolic state and so on. Elucidating the mechanism of antibiotic resistance will be helpful in developing new targeted drugs to effectively eradicate H. pylori. Here, we review the bacteria factors associated with H. pylori antibiotic resistance.

Diagnosis of Helicobacter pylori infection: Current options and developments

Accurate diagnosis of Helicobacter pylori (H. pylori) infection is a crucial part in the effective management of many gastroduodenal diseases. Several invasive and non-invasive diagnostic tests are available for the detection of H. pylori and each test has its usefulness and limitations in different clinical situations. Although none can be considered as a single gold standard in clinical practice, several techniques have been developed to give the more reliable results. Invasive tests are performed via endoscopic biopsy specimens and these tests include histology, culture, rapid urease test as well as molecular methods. Developments of endoscopic equipment also contribute to the real-time diagnosis of H. pylori during endoscopy. Urea breathing test and stool antigen test are most widely used non-invasive tests, whereas serology is useful in screening and epidemiological studies. Molecular methods have been used in variable specimens other than gastric mucosa. More than detection of H. pylori infection, several tests are introduced into the evaluation of virulence factors and antibiotic sensitivity of H. pylori, as well as screening precancerous lesions and gastric cancer. The aim of this article is to review the current options and novel developments of diagnostic tests and their applications in different clinical conditions or for specific purposes.

Recent "omics" advances in Helicobacter pylori

The development of high-throughput whole genome sequencing (WGS) technologies is changing the face of microbiology, facilitating the comparison of large numbers of genomes from different lineages of a same organism. Our aim was to review the main advances on Helicobacter pylori "omics" and to understand how this is improving our knowledge of the biology, diversity and pathogenesis of H. pylori. Since the first H. pylori isolate was sequenced in 1997, 510 genomes have been deposited in the NCBI archive, providing a basis for improved understanding of the epidemiology and evolution of this important pathogen. This review focuses on works published between April 2015 and March 2016. Helicobacter "omics" is already making an impact and is a growing research field. Ultimately these advances will be translated into a routine clinical laboratory setting in order to improve public health.

Correlation of rpsU Gene Sequence Clusters and Biochemical Properties, Gc-Ms Spectra and Resistance Profiles of Clinical Burkholderia Spp. Isolates

This study assessed the variation of phenotypic features of clinical isolates of Burkholderia spp. from common rpsU gene sequence clusters. A total of 41 clinical Burkholderia spp. isolates from German mucoviscidosis patients was subjected to rpsU gene sequencing. Biochemical assessment included the API systems 20 NE and 50 CHE as well as the Micronaut NF system. Fatty acid patterns were assessed using gas chromatography-mass spectrometry (GC-MS). Broth microdilution was used to identify minimum inhibitory concentrations. Five rpsU gene sequence clusters comprised more than one clinical isolate. Altogether, assignments to three species and seven clusters comprising more than one Burkholderia species were performed. Inhomogeneity of biochemical reactions within the clusters ranged from 0/28 to 45/50 reactions. The standard deviation for fatty acid distributions ranged from 0% to 11.5%. Minimum inhibitory concentrations within the clusters showed a wide variation but only minor differences between the clusters. Broad variations within identified rpsU gene sequence clusters regarding biochemical reactions, fatty acid patterns, and resistance patterns of clinical Burkholderia spp. isolates make the application of rpsU gene sequence analysis as a stand-alone procedure for discriminations within the Burkholderia cepacia complex unreliable.

The Bioinformatics Report of Mutation Outcome on NADPH Flavin Oxidoreductase Protein Sequence in Clinical Isolates of H. pylori

frxA gene has been implicated in the metronidazole nitro reduction by H. pylori. Alternatively, frxA is expected to contribute to the protection of urease and to the in vivo survival of H. pylori. The aim of present study is to report the mutation effects on the frxA protein sequence in clinical isolates of H. pylori in our community. Metronidazole resistance was proven in 27 of 48 isolates. glmM and frxA genes were used for molecular confirmation of H. pylori isolates. The primer set for detection of whole sequence of frxA gene for the effect of mutation on protein sequence was used. DNA and protein sequence evaluation and analysis were done by blast, Clustal Omega, and T COFFEE programs. Then, FrxA protein sequences from six metronidazole-resistant clinical isolates were analyzed by web-based bioinformatics tools. The result of six metronidazole-resistant clinical isolates in comparison with strain 26695 showed ten missense mutations. The result with the STRING program revealed that no change was seen after alterations in these sequences. According to consensus data involving four methods, residue substitutions at 40, 13, and 141 increase the stability of protein sequence after mutation, while other alterations decrease. Residue substitutions at 40, 43, 141, 138, 169, and 179 are deleterious, while, V7I, Q10R, V34I, and V96I alterations are neutral. As FrxA contribute to survival of bacterium and in regard to the effect of mutations on protein function, it might affect the survival and bacterium phenotype and it need to be studied more. Also, none of the stability prediction tool is perfect; iStable is the best predictor method among all methods.

Diagnosis of Helicobacter pylori infection: Current options and developments

Accurate diagnosis of Helicobacter pylori (H. pylori) infection is a crucial part in the effective management of many gastroduodenal diseases. Several invasive and non-invasive diagnostic tests are available for the detection of H. pylori and each test has its usefulness and limitations in different clinical situations. Although none can be considered as a single gold standard in clinical practice, several techniques have been developed to give the more reliable results. Invasive tests are performed via endoscopic biopsy specimens and these tests include histology, culture, rapid urease test as well as molecular methods. Developments of endoscopic equipment also contribute to the real-time diagnosis of H. pylori during endoscopy. Urea breathing test and stool antigen test are most widely used non-invasive tests, whereas serology is useful in screening and epidemiological studies. Molecular methods have been used in variable specimens other than gastric mucosa. More than detection of H. pylori infection, several tests are introduced into the evaluation of virulence factors and antibiotic sensitivity of H. pylori, as well as screening precancerous lesions and gastric cancer. The aim of this article is to review the current options and novel developments of diagnostic tests and their applications in different clinical conditions or for specific purposes.