Eradication of Helicobacter pylori in Children Restores the Structure of the Gastric Bacterial Community to That of Noninfected Children

Therapeutic Approach Targeting Gut Microbiome in Gastrointestinal Infectious Diseases

While emerging evidence highlights the significance of gut microbiome in gastrointestinal infectious diseases, treatments like Fecal Microbiota Transplantation (FMT) and probiotics are gaining popularity, especially for diarrhea patients. However, the specific role of the gut microbiome in different gastrointestinal infectious diseases remains uncertain. There is no consensus on whether gut modulation therapy is universally effective for all such infections. In this comprehensive review, we examine recent developments of the gut microbiome's involvement in several gastrointestinal infectious diseases, including infection of Helicobacter pylori, Clostridium difficile, Vibrio cholerae, enteric viruses, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa Staphylococcus aureus, Candida albicans, and Giardia duodenalis. We have also incorporated information about fungi and engineered bacteria in gastrointestinal infectious diseases, aiming for a more comprehensive overview of the role of the gut microbiome. This review will provide insights into the pathogenic mechanisms of the gut microbiome while exploring the microbiome's potential in the prevention, diagnosis, prediction, and treatment of gastrointestinal infections.

Human gastric microbiota transplantation recapitulates premalignant lesions in germ-free mice

OBJECTIVE

Gastric cancer (GC) is a leading cause of cancer-related mortality. Although microbes besides Helicobacter pylori may also contribute to gastric carcinogenesis, wild-type germ-free (GF) mouse models investigating the role of human gastric microbiota in the process are not yet available. We aimed to evaluate the histopathological features of GF mouse stomachs transplanted with gastric microbiota from patients with different gastric disease states and their relationships with the microbiota.

DESIGN

Microbiota profiles in corpus and antrum tissues and gastric fluid from 12 patients with gastric dysplasia or GC were analysed. Thereafter, biopsied corpus and antrum tissues and gastric fluid from patients (n=15 and n=12, respectively) with chronic superficial gastritis, intestinal metaplasia or GC were inoculated into 42 GF C57BL/6 mice. The gastric microbiota was analysed by amplicon sequencing. Histopathological features of mouse stomachs were analysed immunohistochemically at 1 month after inoculation. An independent set of an additional 15 GF mice was also analysed at 1 year.

RESULTS

The microbial community structures of patients with dysplasia or GC in the corpus and antrum were similar. The gastric microbiota from patients with intestinal metaplasia or GC selectively colonised the mouse stomachs and induced premalignant lesions: loss of parietal cells and increases in inflammation foci, in F4/80 and Ki-67 expression, and in CD44v9/GSII lectin expression. Marked dysplastic changes were noted at 1 year post inoculation.

CONCLUSION

Major histopathological features of premalignant changes are reproducible in GF mice transplanted with gastric microbiota from patients with intestinal metaplasia or GC. Our results suggest that GF mice are useful for analysing the causality of associations reported in human gastric microbiome studies.

Effect of Helicobacter Pylori Eradication on Human Gastric Microbiota: A Systematic Review and Meta-Analysis

Background

Helicobacter pylori (H. pylori) infection is a major risk factor for gastric cancer and eradication of H. pylori is recommended as an effective gastric cancer prevention strategy. The infected individuals show microbial dysbiosis of gastric microbiota. In recent years, agrowing number of studies have focused on gastric microbiota changes following H. pylori eradication. In the present study, we aim to evaluate the influence of successful H. pylori eradication on the short-term and long-term alterations of human gastric microbiota using a method of systematic review and meta-analysis.

Methods

We did a systematic search based on three databases (PubMed, EMBASE, and Web of Science) in November 2021. Additional articles were also identified by reviewing references cited in the included papers. Human studies that reported changes in gastric microbiota following successful H. pylori eradication were enrolled. PROSPERO registration number: CRD42021293796.

Results

In total, nine studies enrolling 546 participants were included. Regarding quadruple therapy, alpha diversity indexes increased within 1 month after eradication; significant differences in gastric microbial community structure between before and after eradication were also seen within 1 month. The trends of the above-mentioned diversity changes persisted with a follow-up of 6 months. The microbial composition altered significantly after eradication and the relative abundance of H. pylori-related taxa decreased. Accordingly, gastric commonly dominant commensals were enriched. Bioinformatic analyses of microbiota functions showed that bacteria reproduction-related pathways were down-regulated and pathways of gastric acid secretion, etc. were up-regulated. For triple therapy, similar trends of alpha diversity and beta diversity changes were observed in the short-term and long-term follow-up. Also, after eradication, H. pylori was not the gastric dominant bacteria and similar changes in gastric microbial composition were found. For gastric microbial interactions, a decrease in microbial interactions was seen after eradication. Additionally, regarding whether successful H. pylori eradication could restore gastric microbiota to uninfected status, the results remain controversial.

Conclusion

In conclusion, successful H. pylori eradication could reverse the gastric microbiota dysbiosis and show beneficial effects on gastric microbiota. Our findings may provide new insight for exploring the role of H. pylori and the whole gastric microbiota in gastric carcinogenesis.

Multi-omics reveals microbiome, host gene expression, and immune landscape in gastric carcinogenesis

To date, there has been no multi-omic analysis characterizing the intricate relationships between the intragastric microbiome and gastric mucosal gene expression in gastric carcinogenesis. Using multi-omic approaches, we provide a comprehensive view of the connections between the microbiome and host gene expression in distinct stages of gastric carcinogenesis (i.e., healthy, gastritis, cancer). Our integrative analysis uncovers various associations specific to disease states. For example, uniquely in gastritis, Helicobacteraceae is highly correlated with the expression of FAM3D, which has been previously implicated in gastrointestinal inflammation. In addition, in gastric cancer but not in adjacent gastritis, Lachnospiraceae is highly correlated with the expression of UBD, which regulates mitosis and cell cycle time. Furthermore, lower abundances of B cell signatures in gastric cancer compared to gastritis may suggest a previously unidentified immune evasion process in gastric carcinogenesis. Our study provides the most comprehensive description of microbial, host transcriptomic, and immune cell factors of the gastric carcinogenesis pathway.

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Multi-omics finds genetic, microbial, and immunological links in gastric cancer

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Helicobacteraceae was highly associated with the expression of inflammation genes

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Pasteurellaceae and Lachnospiraceae were associated with cancer-related genes

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B cell infiltration was prominent in gastritis tissues but not in gastric cancer

Helicobacter pylori eradication: Exploring its impacts on the gastric mucosa

Helicobacter pylori (H. pylori) infects approximately 50% of all humans globally. Persistent H. pylori infection causes multiple gastric and extragastric diseases, indicating the importance of early diagnosis and timely treatment. H. pylori eradication produces dramatic changes in the gastric mucosa, resulting in restored function. Consequently, to better understand the importance of H. pylori eradication and clarify the subsequent recovery of gastric mucosal functions after eradication, we summarize histological, endoscopic, and gastric microbiota changes to assess the therapeutic effects on the gastric mucosa.

Interactions between H. pylori and the Gastric Microbiome: Impact on Gastric Homeostasis and Disease

Like many seemingly inhospitable environments on our planet, the highly acidic human stomach harbors a diverse bacterial microflora. The best-known member of the human gastric flora, Helicobacter pylori, causes a number of gastric diseases, including peptic ulcer disease and gastric adenocarcinoma. In the absence of Helicobacter pylori infection, the gastric microbiota displays some features similar to the oral cavity with Firmicutes the most common phylum, followed by Proteobacteria and Bacteroidetes. When present, H. pylori dominates the gastric microbiome and reduces diversity and composition of other taxa. The composition of the gastric microbiome also is altered in the setting of proton pump inhibitor therapy and gastric neoplasia. This review summarizes foundational and recent studies that have investigated the composition of the human gastric microbiome in a variety of patient groups, with a focus on potential mechanisms involved in regulation of gastric microbial community structure.

Helicobacter pylori infection and eradication: Exploring their impacts on the gastrointestinal microbiota

The rapid development of microbiota research has remolded our view of human physiological and pathological processes. Among all the gastrointestinal microorganisms, Helicobacter pylori (H pylori) is probably the most notorious constituent. Although half of the adults worldwide are infected with H pylori, their clinical manifestations vary widely, suggesting other microorganisms beyond H pylori may play a role in determining clinical outcomes. Recently, many studies have put effort into elucidating the crosstalk within the human microbiota, some of which specifically explored the interplay between H pylori and other gastrointestinal microbial members. In this work, we reviewed these potential interactions. Meanwhile, the impacts of H pylori eradication therapy on gastrointestinal microbial homeostasis were summarized in terms of diversity, composition, functional capacity, and antibiotic resistance.

MALDI-TOF MS and 16S RNA Identification of Culturable Gastric Microbiota: Variability Associated with the Presence of Helicobacter pylori

Helicobacter pylori is the main bacteria associated with gastroduodenal diseases. Recent studies have reported that gastric microbiota might be modified by the H. pylori colonization, favoring gastric lesions′ development. In Chile, the region of La Araucanía concentrates a high risk of gastric cancer associated with Helicobacter pylori colonization, rurality, poverty, and Mapuche ethnicity. Hence, we aimed to identify the culturable gastric microbiota and characterize its variability at different stages of epithelial injury, based on its H. pylori colonization in dyspeptic patients from this Chilean region. Microaerophilic bacteria strains were isolated from antrum biopsies of 155 dyspeptic patients′ biopsies and identified using MALDI-TOF MS or 16sRNA gene sequencing for non-pylori species identification, and UreC gene amplification for H. pylori confirmation. We found 48 species from 18 families, mainly belonging to Neisseriaceae (21.3%), Streptococcaceae (20.0%), Actynomicetaceae (9.0%), Enterobacteriaceae, and Lactobacillaceae (4.5%); however, Streptococcaceae and Actinomycetaceae families showed a significant reduction in samples infected with H. pylori, along with a considerably lower diversity of species. Our results revealed a microbiota modification due to H. pylori colonization associated with the gastric epithelial state, suggesting a potential microbiota role for developing and progressing gastric diseases.

Management of Helicobacter pylori

PURPOSE OF REVIEW

Gastroenterologists and many general internists and primary care physicians confront questions regarding the management of Helicobacter pylori on a daily basis. The subject remains of global interest and continue to generate debate and research. Using the search terms 'pylori and treatment' or 'pylori and management' we identified over 1000 relevant articles in PubMed published over the time period 1 January 2019 to 30 April 2020. We have selected the most highly clinically relevant of these to review here.

RECENT FINDINGS

Clinical evidence grows regarding the benefits of H. pylori eradication on gastric cancer prevention. High rates of resistance to clarithromycin and levofloxacin, correlating with treatment failure in regimens utilizing these drugs, has stimulated interest in alternative regimens as well as the need for susceptibility testing of individual patients and populations. Although many aspects of H. pylori management are well established, implementation of appropriate testing and treatment pathways remains suboptimal throughout healthcare settings.

SUMMARY

Increased emphasis on measuring H. pylori-related clinical outcomes in practice is needed to identify implementation gaps, and to suggest means to best apply the knowledge gained on H. pylori for the prevention of gastric symptoms and disease.

Changes in Gastric Microbial Composition before and after Helicobacter pylori Eradication Therapy

Owing to advancements in next-generation sequencing and non-culture-based microbial research techniques, we have recognized that many bacterial taxa other than <i>Helicobacter pylori (H. pylori)</i> are present in the human stomach. Gastric microbial composition depends on gastric diseases, including gastritis, atrophic gastritis, intestinal metaplasia, and gastric cancer. Although <i>H. pylori</i> is a major factor associated with gastric cancer development, other bacterial taxa may affect gastric carcinogenesis. Because the risk of gastric cancer development can be reduced through <i>H. pylori</i> eradication, many investigators have studied the changes in the microbial composition in the stomach after <i>H. pylori</i> eradication. The gastric microbiome in patients with <i>H. pylori</i> infection typically shows abundance of <i>H. pylori</i> and a low microbial diversity index. If we treat <i>H. pylori</i>-infected patients with antibiotics, microbial diversity increases, and the relative abundance also increases in many bacterial taxa. Several studies suggested that the microbial composition in patients with <i>H. pylori</i> infection could be restored by <i>H. pylori</i> eradication therapy; however, there have been inconsistent findings of the abundant bacterial taxa after <i>H. pylori</i> eradication in patients with atrophic gastritis and intestinal metaplasia. More studies are required to reach a definitive conclusion on restoration of the microbial composition after <i>H. pylori</i> eradication according to the severity of gastric inflammation.

Diagnosis and treatment of Helicobacter pylori infections in children and elderly populations

Helicobacter pylori (H. pylori) infection is associated with various gastric and extra-gastric diseases. Importantly, this infection is the strongest known risk factor for gastric cancer (GC). H. pylori eradication can effectively prevent H. pylori infection-associated diseases in H. pylori-positive patients, including children and elderly subjects. However, a limited selection of antibiotics, a higher reinfection rate, and certain spontaneous clearance rates, to some extent, restrict the choice of H. pylori treatments in pediatrics. In addition, it is imperative to perform an accurate diagnosis of H. pylori infection in children by determining the presence of the H. pylori infection and the underlying cause of symptoms. In elderly patients, poor tolerance to drugs and higher sensitivity to adverse effects are major concerns during H. pylori therapy. Recent studies have demonstrated that H. pylori eradication could significantly lower the GC risk in the elderly population. The benefit and risk of H. pylori eradication in elderly patients should be comprehensively considered and balanced. If available, susceptibility-based tailored therapies may be preferable in eradicating H. pylori. In addition, to increase the eradication rate and reduce adverse effects, new therapeutic strategies (e.g., probiotic supplementation, berberine supplementation, dual therapy) for H. pylori infection are being extensively investigated. The impact of H. pylori eradication with antibiotics on the microbiota in children has been explored, but further high-quality studies are crucial to delineate the extent of H. pylori eradication affecting the microbial community in children. In this review, we summarize the current understanding of H. pylori diagnosis and treatment in children and the elderly population and aim to provide insights into the efficient management and treatment implementation in these populations.