The Prevalence of Helicobacter pylori Virulence Factors in Bhutan, Vietnam, and Myanmar Is Related to Gastric Cancer Incidence

Emergence of amoxicillin resistance and identification of novel mutations of the pbp1A gene in Helicobacter pylori in Vietnam

Background

Amoxicillin-resistant Helicobacter pylori (H. pylori) strains seem to have increased over time in Vietnam. This threatens the effectiveness of H. pylori eradication therapies with this antibiotic. This study aimed to investigate the prevalence of primary resistance of H. pylori to amoxicillin and to assess its association with pbp1A point mutations in Vietnamese patients.

Materials and methods

Naive patients who presented with dyspepsia undergoing upper gastrointestinal endoscopy were recruited. Rapid urease tests and PCR assays were used to diagnose H. pylori infection. Amoxicillin susceptibility was examined by E-tests. Molecular detection of the mutant pbp1A gene conferring amoxicillin resistance was carried out by real-time PCR followed by direct sequencing of the PCR products. Phylogenetic analyses were performed using the Tamura-Nei genetic distance model and the neighbor-joining tree building method.

Results

There were 308 patients (46.1% men and 53.9% women, p = 0.190) with H. pylori infection. The mean age of the patients was 40.5 ± 11.4 years, ranging from 18 to 74 years old. The E-test was used to determine the susceptibility to amoxicillin (minimum inhibitory concentration (MIC) ≤ 0.125 μg/ml) in 101 isolates, among which the rate of primarily resistant strains to amoxicillin was 25.7%. Then, 270 sequences of pbp1A gene fragments were analysed. There were 77 amino acid substitution positions investigated, spanning amino acids 310–596, with the proportion varying from 0.4 to 100%. Seven amino acid changes were significantly different between amoxicillin-sensitive (Amox^S) and amoxicillin-resistant (Amox^R) samples, including Phe₃₆₆ to Leu (p <  0.001), Ser₄₁₄ to Arg (p <  0.001), Glu/Asn_464–465 (p = 0.009), Val₄₆₉ to Met (p = 0.021), Phe₄₇₃ to Val (p <  0.001), Asp₄₇₉ to Glu (p = 0.044), and Ser/Ala/Gly_595–596 (p = 0.001). Phylogenetic analyses suggested that other molecular mechanisms might contribute to amoxicillin resistance in H. pylori in addition to the alterations in PBP1A.

Conclusions

We reported the emergence of amoxicillin-resistant Helicobacter pylori strains in Vietnam and new mutations statistically associated with this antimicrobial resistance. Additional studies are necessary to identify the mechanisms contributing to this resistance in Vietnam.

Helicobacter pylori Virulence Factor Genotyping

Helicobacter pylori (H. pylori) infection causes chronic gastritis, peptic ulcers, gastric adenocarcinoma, and mucosa-associated lymphoid tissue (MALT) lymphoma. Bacterial, host, and environmental factors influence the progression of disease from superficial gastritis to cancer. H. pylori is genetically diverse, and expression of its specific virulence factors has been linked to increased risk of more severe pathologies. Described in this chapter is a protocol for detecting important H. pylori virulence factors by firstly extracting DNA from culture material or stomach tissue biopsies, followed by PCR amplification and agarose gel electrophoresis.

Detection of Helicobacter pylori and its virulence genes (cagA, dupA, and vacA) among patients with gastroduodenal diseases in Chris Hani Baragwanath Academic Hospital, South Africa

BACKGROUND

The global prevalence of H. pylori approaches 50%, with prevalence rates between 20 and 40% in developed countries and up to 90% in Africa and other developing nations of the world. Development of H. pylori-associated diseases is determined by a number of virulence factors. This study aimed at determining the prevalence of H. pylori infections and virulence genes (cagA, dupA, and vacA); the relationship between virulence factors and gastroduodenal diseases among patients.

METHODS

Gastric biopsies were obtained from patients and cultured, DNA was extracted from cultured isolates and biopsies for PCR assay after which samples were investigated using standard laboratory procedures. Data of associated risk factors were obtained with the aid of questionnaires.

RESULTS

Of the 444 participants, H. pylori was detected in 115 (25.9%) from culture analysis and 217 (48.9%) by direct PCR method. Ninety-eight (85.2%) of the culture-positive patients were also detected by PCR giving an overall prevalence of 52.7% (234/444). The highest number of H. pylori isolates 76.9% (180/234) was obtained from patients suffering from pangastritis. The CagA virulence gene was found in 62% (145/234), dupA in 53.4% (125/234) and vacA in 90.6% (212/234). VacA genotype s1 m1 was the most prevalent [56.4% (132)] followed by s2 m2 [11.5% (27)], s2 m1 [10.3% (24)] and [s1 m2 9.4% (22)]. There was a significant association observed in vacA s1 and peptic ulcer disease, as well as vacA s1/m2 and gastric erosion (P < 0.05).

CONCLUSION

The study revealed a significant association between virulence genes and the development of certain forms of gastric infections while the variations in H. pylori detection and the associated risk factors investigated in the study were not significantly related.

Effects of periodontal therapy on eradication and recurrence of Helicobacter pylori infection after successful treatment

OBJECTIVES

This study aimed to evaluate the effects of periodontal therapy on the efficacy of Helicobacter pylori eradication and on the recurrence of infection after eradication.

METHODS

We conducted a prospective randomized trial on 698 gastric H. pylori-infected patients, of whom 347 received gastric H. pylori treatment alone and 342 received gastric H. pylori treatment plus periodontal therapy. The presence of H. pylori and associated virulence genes were detected by real-time polymerase chain reaction.

RESULTS

After eradication of gastric H. pylori infection, the recurrence of gastric H. pylori was significantly lower in the gastric H. pylori treatment plus periodontal therapy group than in the group receiving gastric H. pylori treatment alone (OR 0.67; 95% CI 0.45 to 0.99), whereas the eradication rate was not significantly different (OR 0.87; 95% CI 0.68 to 0.98). There was a close relationship between the presence of H. pylori in saliva and its presence in the stomach.

CONCLUSIONS

The oral cavity is an important reservoir for gastric H. pylori infection. Adjunctive periodontal therapy could enhance the efficiency of H. pylori treatment and reduce the recurrence of gastric H. pylori infection.

New observations regarding Helicobacter pylori and gastric cancer in Mongolia

BACKGROUND

The incidence and mortality of gastric cancer in Mongolia is among the highest in the world.

METHODS

This was a case-control study in which upper gastrointestinal endoscopy, gastric histology, Helicobacter pylori testing, and risk factor questionnaires were obtained. Histologic subtypes were determined by Lauren's classification.

RESULTS

We enrolled 45 gastric cancer and 108 non-gastric cancer patients. Gastric cancers were located in upper part of stomach in 53.3%, main gastric body in 37.8%, and lower part of stomach in 8.9%. The majority (60%) were diffuse type, followed by intestinal type (36.7%) and indeterminate type (3.3%). H. pylori infections were CagA positive in 100% with cancer vs 81% without cancer (P = .02). The majority of CagA was non-East Asian type (95% with cancer and 94.1% without cancer). Cancer patients had typically related with excessive use of salt, hot beverages, tobacco smoking, and low ingestion of fruits.

CONCLUSION

The characteristic topography of gastric cancer in Mongolia being in the gastric corpus differed from East Asian countries and was more similar to western countries. The risk factors for gastric cancer in Mongolia were similar to other high-risk areas (ie, H. pylori infection, excessive use of salt, tobacco smoking, and low ingestion of fruits).

The Endoscopic and Clinicopathological Characteristics of Early-onset Gastric Cancer in Vietnamese Patients

Aim: To assess the endoscopic and clinicopathological features of early-onset gastric cancer (EOGC) in Vietnamese, a population with intermediate risk of gastric cancer. Patients and methods: Consecutive patients diagnosed with gastric adenocarcinoma were prospectively recruited. The demographic, clinical data in each patient were collected. The location and macroscopic type of all gastric lesions suspected to be malignant were reported according to the Japanese classification. The histologic tumor type of gastric cancer (GC) was classified according to the Lauren classification. Helicobacter pylori (H. pylori) infection were diagnosed by rapid urease test and urinary H. pylori antibody test. The infection was diagnosed when at least one of the two tests was positive. Results: The rate of EOGC (i.e. ≤ 40 years of age) was 16.3% (23/141). The median age of patients with EOGC was 35 (range 28 – 40) years and the male-to-female was 1:1.09. Compared to the older group (i.e. ≥ 50 years of age), the rates of positive family history, H. pylori infection and alarm features in the EOGC group were not significantly different (0.0% vs. 5.4%, p = 0.581; 73.9% vs. 66.3%, p = 0.620; and 60.8% vs. 79.3%, p = 0.100; respectively). The EOGC group had significantly higher rate of tumor extending to entire stomach (21.7% vs. 3.4%, p = 0.003); but the rate of diffuse-type GC between the two groups were not significantly different (87.0% vs. 71.7%, p = 0.181). Conclusions: Vietnamese patients with EOGC had higher rate of tumor extending to entire stomach compared to the older group. But the family history of GC, H. pylori infection and the pathological characteristics were not significantly different between the two groups. Environmental factors which play important roles in the development of EOGC in Vietnam should be investigated in future study.

Risk of gastric cancer in association with Helicobacter pylori different virulence factors: A systematic review and meta-analysis

INTRODUCTION

It has been proposed that specific analysis of Helicobacter pylori virulence factors can be suitable for predicting of post H. pylori infection disorders like gastric cancer (GC). The present study was designed to evaluate the association between different virulence factors of H. pylori and GC.

METHODS

Studies investigated the association between virulence factors of H. pylori and GC were collected from the several databases. All analysis was performed by Comprehensive Meta-Analysis V2.2 software (Biostat, Englewood, NJ, USA).

RESULTS

Based on a comprehensive literature search, 25 eligible studies were included for meta-analyses. Infection with cagA- and vacA s1m1-positive H. pylori strains were significantly associated with increased risk of GC (OR of [2.82 (95% CI 1.96-4.06), P < 0.001]) and ([1.75 (95% CI 1.04-2.96), P 0.034)], respectively.

CONCLUSIONS

Infection by H. pylori strains with positive vacA s1m1 and the cagA genes can significantly increase the risk of GC. The association between the vacA s1m1 and the cagA and GC, suggests that screening of these genes may be helpful for identifying populations at higher risk for GC.

Serum VEGF Levels in Helicobacter pylori Infection and Correlation with Helicobacter pylori cagA and vacA Genes

BACKGROUND:

Helicobacter pylori vacA and cagA genes are associated with higher virulence. Vascular Endothelial Growth Factor (VEGF) is one important marker for neo-angiogenesis.

AIM:

The purpose of this study was to investigate the relationship between VEGF serum levels with cagA and vacA genes in H. pylori infection.

METHODS:

A cross-sectional study was done on eighty patients that consecutive admitted to endoscopy unit. The diagnosis of H. pylori infection was based on rapid urease test. Serum samples were obtained to determine circulating VEGF level. Polymerase chain reaction was done to examine H. pylori vacA and cagA genes. Data analysis were carried-out using SPSS version 22.

RESULTS:

A total of 80 patients were examined. There were 45 (56.3%) patients infected with Helicobacter pylori. There were 33 (73.3%) patients with H. pylori cagA positive. Serum VEGF levels in patients with the H. pylori positive were significantly higher compared to the patients that have no H. pylori. Serum levels of VEGF were significantly higher in cagA positive than negative.

CONCLUSION:

Serum VEGF level is correlated with H. pylori infection and its virulence status. The more virulence of H. pylori, cagA gene, the higher serum VEGF levels were found.

Epidemiology of Helicobacter pylori infection

This review of recent publications related to the epidemiology of Helicobacter pylori highlights the origin of the infection, its changing prevalence, transmission, and outcome. A number of studies have addressed the ancestor roots of the bacteria, and the first genomewide analysis of bacterial strains suggests that its coexistence with humans is more ancient than previously thought. As opposed to the generally declining prevalence of H. pylori (including China and Japan), in Sweden, the prevalence of atrophic gastritis in the young population has risen. The prevalence of the infection remains high in the indigenous populations of the Arctic regions, and reinfection rates are high. A high prevalence is permanently found in the Siberian regions of Russia as well. Several studies, some of which used multiplex serology, addressed prevalence of and risks associated with various H. pylori serotypes, thereby enabling more precise risk assessment. Transmission of H. pylori was discussed, specifically fecal-oral transmission and the use of well-water and other unpurified water. Finally, the long-term course of H. pylori infection was considered, with an estimated 89% of noncardia gastric cancer cases being attributable to the infection.

Relationship between vacA Types and Development of Gastroduodenal Diseases

The Helicobacter pylori vacuolating cytotoxin (VacA) is a secreted pore-forming toxin and a major virulence factor in the pathogenesis of H. pylori infection. While VacA is present in almost all strains, only some forms are toxigenic and pathogenic. While vacA and its genotypes are considered as markers of H. pylori-related diseases or disorders, the pathophysiological mechanisms of VacA and its genotypes remain controversial. This review outlines key findings of publications regarding vacA with emphasis on the relationship between vacA genotypes and the development of human disease.

The changing epidemiology of Asian digestive cancers: From etiologies and incidences to preventive strategies

Digestive cancers are a major health burden in Asia. Due to the presence of similar "infection-inflammation-cancer" pathways in the carcinogenesis process, eradicating infective pathogens or attenuating relevant inflammatory signaling pathways may reduce digestive cancer incidences and improve patient outcomes. The aim of this paper is to review the recent evidence regarding the epidemiology of three major digestive cancers in Asia: stomach cancer, liver cancer, and colorectal cancer. We focused on the incidence trends, the major etiologies, and especially the potential preventive strategies.