Duodenal ulcer promoting gene 1 (dupA1) is associated with A2147G clarithromycin-resistance mutation but not interleukin-8 secretion from gastric mucosa in Iraqi patients

A study of prevalence and risk factors for Helicobacter pylori infection among adults in Duhok Province, Kurdistan Region, Iraq

Helicobacter pylori is known to increase the risk of developing gastritis, peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma in adults across the globe. The present study aimed to determine the prevalence of H. pylori infection and its associated risk factors. This cross-sectional study was conducted among the adult population in Duhok Province, Kurdistan Region, Iraq. A total of 259 subjects over the age of 18 who visited the hospitals were included in the study from 2018 to 2020. An enzyme-linked immunosorbent assay was utilized to determine H. pylori seropositivity. A standardized questionnaire was administered to all study participants through face-to-face interviews. The H. pylori immunoglobulin G (IgG) antibody data were analyzed using the Chi-square test. The prevalence of anti-H. pylori IgG antibody was present in 40.02% of adults. Among the studied variables, the following risk factors were significantly associated with the presence of anti-H. pylori IgG antibodies: male gender (P<0.043), level of education (P<0.025), history of gastrointestinal diseases (P<0.001), smoking status (P<0.001), and more siblings (P<0.001). This study supports the hypothesis that H. pylori infection in adults is highly related to poor hygiene and smoking status, low level of education, and crowded conditions. Therefore, in order to reduce the prevalence of H. pylori infection among adults, it is crucial to implement effective strategies aimed at enhancing fundamental sanitary conditions, as well as improving educational and socioeconomic status.

Clinical relevance of the cagA and vacA s1m1 status and antibiotic resistance in Helicobacter pylori: a systematic review and meta-analysis

BACKGROUND

The role of Helicobacter pylori (H. pylori) virulence factors of such as vacA s1m1 and cagA in designating clinical outcomes and eradication rate has been deeply challenged in the last decade. The goal of this analysis was to identify the potential relevance between cagA and vacA genotypes with reported antibiotic resistance observed in clinical H. pylori isolates.

METHODS

This literature search was conducted in databases such as Clarivate analytics, PubMed, Scopus, EMBASE, DOAJ, and Google Scholar by April 2022, regardless of language restrictions and publication date. Quality of the included studies was assessed by the Newcastle-Ottawa scale. Statistical analysis of retrieved studies was fulfilled using Comprehensive Meta-Analysis software version 2.2. Following quality appraisal of eligible studies, potential association between the status of cagA and vacA genes with resistance to clarithromycin, metronidazole, amoxicillin, tetracycline, and levofloxacin was measured using odds ratio with 95% confidence interval. We also used sensitivity analyses and meta-regression to eliminate the source of heterogeneity from the overall estimates. Publication bias was assessed using funnel plot, Egger's test, Begg's test with the trim and fill procedure to assess the presence and magnitude of publication bias in the included studies.

RESULTS

Our findings suggested that a significant relationship between cagA status ‎and increase resistance ‎to metronidazole (OR: 2.69; 95% CI: 1.24-5.83‎‏‎). In subgroup analysis, we ‎found that in the Western ‎population, infection with cagA-positive strains could be led to increase in ‎the resistance to ‎metronidazole (OR: 1.59; 95% CI: ‎0.78-3.21‎‏‎), ‎amoxicillin (OR: ‎19.68‎; 95% CI: 2.74-‎‎141.18), ‎and ‎levofloxacin (OR: ‎11.33; 95% CI: ‎1.39-‎‎91.85). After implementation of trim and fill method, the adjusted OR was not significantly differed from original estimates which in turn represented our subgroup analysis was statistically robust. On the other hand, vacA ‎genotypes usually ‎reduce the antibiotic resistance of this bacterium, so that vacA s1m1 significantly reduces the ‎resistance to ‎metronidazole (OR: 0.41; 95% CI: 0.20-0.86‎‏‎). Surprisingly, resistance of vacA s2m2 strains to antibiotics was low, the reason may be due ‎to the non-inflammatory properties of strains containing vacA s2m2. The meta-regression and sensitivity analyses successfully reduced the effect of heterogeneity from the overall estimates. In addition, although the pooled OR is reduced after trim and fill adjustment but results do not change the conclusion regarding vacA genotypes and antibiotic resistance.

CONCLUSIONS

According to our findings, it was clearly demonstrated that cagA-positive strains are resistance to metronidazole, especially in Western countries. In Western countries, vacA s1m1 increases resistance to amoxicillin and levofloxacin. Based on the present findings, the vacA s1m1 genotype significantly increases resistance to metronidazole, while the vacA s1m2 decreases resistance to clarithromycin and metronidazole. Resistance to antibiotics in less virulent (vacA s2m2) strains is statistically significant lower than others.

Antimicrobial resistance patterns and genetic elements associated with the antibiotic resistance of Helicobacter pylori strains from Shanghai

BACKGROUND

Shanghai, in east China, has one of the world's highest burdens of Helicobacter pylori infection. While multidrug regimens can effectively eradicate H. pylori, the increasing prevalence of antibiotic resistance (AR) in H. pylori has been recognized by the WHO as 'high priority' for urgent need of new therapies. Moreover, the genetic characteristics of H. pylori AR in Shanghai is under-reported. The purpose of this study was to determine the resistance prevalence, re-substantiate resistance-conferring mutations, and investigate novel genetic elements associated with H. pylori AR.

RESULTS

We performed whole genome sequencing and antimicrobial susceptibility testing of 112 H. pylori strains isolated from gastric biopsy specimens from Shanghai patients with different gastric diseases. No strains were resistant to amoxicillin. Levofloxacin, metronidazole and clarithromycin resistance was observed in 39 (34.8%), 73 (65.2%) and 18 (16.1%) strains, respectively. There was no association between gastroscopy diagnosis and resistance phenotypes. We reported the presence or absence of several subsystem protein coding genes including hopE, hofF, spaB, cagY and pflA, and a combination of CRISPRs, which were potentially correlated with resistance phenotypes. The H. pylori strains were also annotated for 80 genome-wide AR genes (ARGs). A genome-wide ARG analysis was performed for the three antibiotics by correlating the phenotypes with the genetic variants, which identified the well-known intrinsic mutations conferring resistance to levofloxacin (N87T/I and/or D91G/Y mutations in gyrA), metronidazole (I38V mutation in fdxB), and clarithromycin (A2143G and/or A2142G mutations in 23S rRNA), and added 174 novel variations, including 23 non-synonymous SNPs and 48 frameshift Indels that were significantly enriched in either the antibiotic-resistant or antibiotic-susceptible bacterial populations. The variant-level linkage disequilibrium analysis highlighted variations in a protease Lon with strong co-occurring correlation with a series of resistance-associated variants.

CONCLUSION

Our study revealed multidrug antibiotic resistance in H. pylori strains from Shanghai, which was characterized by high metronidazole and moderate levofloxacin resistance, and identified specific genomic characteristics in relation to H. pylori AR. Continued surveillance of H. pylori AR in Shanghai is warranted in order to establish appropriate eradication treatment regimens for this population.

Helicobacter pylori-Mediated Oxidative Stress and Gastric Diseases: A Review

Gastric cancer is considered to be a type of gastrointestinal tumor and is mostly accompanied by Helicobacter pylori (HP) infection at the early stage. Hence, the long-term colonization of the gastric mucosa by HP as a causative factor for gastrointestinal diseases cannot be ignored. The virulence factors secreted by the bacterium activate the signaling pathway of oxidative stress and mediate chronic inflammatory response in the host cells. The virulence factors also thwart the antibacterial effect of neutrophils. Subsequently, DNA methylation is induced, which causes continuous cell proliferation and evolution toward low-grade-differentiated gastric cells. This process provides the pathological basis for the occurrence of progressive gastric cancer. Therefore, this review aims to summarize the oxidative stress response triggered by HP in the gastric mucosa and the subsequent signaling pathways. The findings are expected to help in the formulation of new targeted drugs for preventing the occurrence of early gastric cancer and its progression to middle and advanced cancer.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

Novel virulence factor dupA of Helicobacter pylori as an important risk determinant for disease manifestation: An overview

Helicobacter pylori (H. pylori) is a microaerophilic, Gram-negative, human gastric pathogen found usually in the mucous lining of stomach. It infects more than 50% of the world’s population and leads to gastroduodenal diseases. The outcome of disease depends on mainly three factors: Host genetics, environment and bacterial factors. Among these, bacterial virulence factors such as cagA, vacA are well known for their role in disease outcomes. However, based on the global epidemiological results, none of the bacterial virulence (gene) factors was found to be associated with particular diseases like duodenal ulcer (DU) in all populations. Hence, substantial importance has been provided for research in strain-specific genes outside the cag pathogenicity island, especially genes located within the plasticity regions. dupA found within the plasticity regions was first demonstrated in 2005 and was proposed for duodenal ulcer development and reduced risk of gastric cancer in certain geographical regions. Due to the discrepancies in report from different parts of the world in DU development related to H. pylori virulence factor, dupA became an interesting area of research in elucidating the role of this gene in the disease progression. In this review, we shed light on the detailed information available on the polymorphisms in dupA and their clinical relevance. We have critically appraised several pertinent studies on dupA and discussed their merits and shortcomings. This review also highlights dupA gene as an important biomarker for DU in certain populations.

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.

Antimicrobial susceptibility testing before first-line treatment for Helicobacter pylori infection in patients with dual or triple antibiotic resistance

AIM

To evaluate the efficacy of antimicrobial susceptibility-guided therapy before first-line treatment for infection in patients with dual or triple antibiotic resistance.

METHODS

A total of 1034 patients infected by Helicobacter pylori (H. pylori) during 2013-2014 were tested for antimicrobial susceptibility. 157 of 1034 (15%) patients showed resistance to two (127/1034; 12%) and to three (30/1034; 3%) antibiotics. Sixty-eight patients with dual H. pylori-resistance (clarithromycin, metronidazole or levofloxacin) were treated for 10 d with triple therapies: OAL (omeprazole 20 mg b.i.d., amoxicillin 1 g b.i.d., and levofloxacin 500 mg b.i.d.) 43 cases, OAM (omeprazole 20 mg b.i.d., amoxicillin 1 g b.i.d., and metronidazole 500 mg b.i.d.) 12 cases and OAC (omeprazole 20 mg b.id., amoxicillin 1 g b.i.d., and clarithromycin 500 mg b.i.d.) 13 cases based on the antimicrobial susceptibility testing. Twelve patients showed triple H. pylori-resistance (clarithromycin, metronidazole and levofloxacin) and received for 10 d triple therapy with OAR (omeprazole 20 mg b.id., amoxicillin 1 g b.i.d., and rifabutin 150 mg b.i.d.). Eradication was confirmed by 13C-urea breath test. Adverse effects and compliance were assessed by a questionnaire.

RESULTS

Intention-to-treat eradication rates were: OAL (97.6%), OAM (91.6%), OAC (92.3%) and OAR (58.3%). Cure rate was significantly higher in naïve patients treated with OAR-10 compared to patients who had two or three previous treatment failures (83% vs 33%). Adverse events rates for OAL, OAM, OAC and OAR were 22%, 25%, 23% and 17%, respectively, all of them mild-moderate.

CONCLUSION

Antimicrobial susceptibility-guided triple therapies during 10 d for first-line treatment leads to an eradication rate superior to 90% in patients with dual antibiotic H. pylori resistance.

VacA and CagA Status as Biomarker of Two Opposite End Outcomes of Helicobacter pylori Infection (Gastric Cancer and Duodenal Ulcer) in a Moroccan Population

Helicobacter pylori (H. pylori) infection induces inflammation of the gastric mucosa, which may progress to precancerous lesions leading to gastric cancer. Pathological determinism is associated to some virulence genes of the bacterium, notably the vacA and cagA genes. The present study aimed to determine the H. pylori genotypes distribution and their association with sex, age and gastric diseases in a Moroccan population. Gastric biopsy was taken from 1079 consenting patients. The specimens were processed by PCR to identify H. pylori and to determine the genotypic profile by PCR characterizing vacA s, vacA m and vacA i regions directly from biopsies H. pylori positives. VacA genotyping revealed the predominance of vacA m2 (53.2%), vacA s2 (52.9%) and vacA i2 (52%). The most virulent vacA alleles (s1, i1 and m1) are more predominant in men (47.3%, 41.9% and 46.1% respectively) than in women (38.3%, 33.3% and 37% respectively). However, the association between vacA genotypes and age did not reach a statistical significant value. Logistic regression analysis results show that vacA i1m1 and vacA i1m2 genotypes were strongly associated with the risk of GC, the Odds Ratio (95% confidence interval) was 29.73 [5.08-173.73] and 9.17 [2.06-40.82] respectively, while vacAs1/cagA+ seems to be a risk factor for DU since it is inversely associated with GC (OR was 0.13 [0.02-0.75]. The results of this study suggest that vacA i1 genotype independently to vacAm status may be of a clinical usefulness and will help to identify patients at a high risk of GC development.

Role of dupA in virulence of Helicobacter pylori

Helicobacter pylori (H. pylori) is a gastric human pathogen associated with acute and chronic gastritis, 70% of all gastric ulcers, 85% of all duodenal ulcers, and both forms of stomach cancer, mucosal-associated lymphoid tissue (MALT) lymphoma and adenocarcinoma. Recently, attention has focused on possible relationship between presence of certain virulence factor and H. pylori-associated diseases. Some contradictory data between this bacterium and related disorders has been observed since not all the colonized individuals develop to severe disease. The reported diseases plausibility related to H. pylori specific virulence factors became an interesting story about this organism. Although a number of putative virulence factors have been identified including cytotoxin-associated gene a (cagA) and vacA, there are conflicting data about their actual participation as specific risk factor for H. pylori-related diseases. Duodenal ulcer promoting gene a (dupA) is a virulence factor of H. pylori that is highly associated with duodenal ulcer development and reduced risk of gastric cancer. The prevalence of dupA in H. pylori strains isolated from western countries is relatively higher than in H. pylori strains from Asian countries. Current confusing epidemiological reports will continue unless future sophisticated and molecular studies provide data on functional and complete dupA cluster in H. pylori infected individuals. This paper elucidates available knowledge concerning role of dupA in virulence of H. pylori after a decade of its discovery.

Clarithromycin Resistance Mutations in Helicobacter pylori in Association with Virulence Factors and Antibiotic Susceptibility of the Strains

Antibiotic resistance is the major cause for Helicobacter pylori eradication failure. H. pylori clarithromycin resistance mutations were evaluated in 84 (82 phenotypically clarithromycin resistant and 2 intermediately susceptible) strains by allele-specific PCR and 3'-mismatched PCR. Many (57.1%) of these strains were metronidazole resistant. Prevalence of cagA(+), cagE(+), vacA s1a, m1, i1, and i2 strains was 76.2%, 58.0%, 82.1%, 35.7%, 50.0%, and 50.0%, respectively. A2143G, A2142G, A2142C, and A2143G+A2142G mutation rates were 64.3%, 23.8%, 1.2%, and 10.7%, respectively. Strains harboring the A2142G mutation showed 5.3-fold higher clarithromycin MIC50 than those harboring the A2143G mutation. The A2143G mutation alone was 1.7-fold more common in vacA i2 strains compared with vacA i1 strains, while the A2142G mutation alone was 3-fold more frequent in vacA i1 strains than vacA i2 strains and 3.1-fold more common in metronidazole-susceptible compared with metronidazole-resistant strains. Briefly, clarithromycin resistance mutations were significantly linked to vacA i allele and metronidazole susceptibility. This is the first report about associations between the A2143G mutation and less virulent vacA i2 strains, and between the A2142G mutation and more virulent vacA i1 strains. As the 2143G mutation often predicts eradication failure by clarithromycin-based regimens, the results may be linked to the better eradication of more virulent strains compared with the less virulent strains.