Structure of the human gastric bacterial community in relation to Helicobacter pylori status

Distinct planting patterns exert legacy effects on the networks and assembly of root-associated microbiomes in subsequent crops

Soil legacy effects from previous crops can significantly influence plant-soil interactions in crop rotations. However, the microbial mechanism underlying this effect in subsequent root-associated compartments remains unclear. We investigated the effects of planting patterns (four-year continuous maize [MM], three-year winter wheat and one-year maize rotation [WM], and three-year potato and one-year maize rotation [PM]) on the microbial composition and structure of root-associated compartments, the effect of distinct crops on subsequent microbial co-occurrence patterns, and the assembly mechanism by which the root-associated compartments (bulk soil, rhizosphere, and roots) in subsequent crops regulate the microbiome habitat. Compared with MM, the relative abundance of Acidobacteria in WM was 29.7 % lower, whereas that of Bacteroidota in PM was 37.9 % higher in all three compartments. The co-occurrence patterns of the microbial communities exhibited varied responses to different planting patterns. Indicator taxon analysis revealed less shared and specific species in the root bacterial and fungal networks. The planting pattern elicited specific responses from modules within bacterial and fungal co-occurrence networks in all three compartments. Moreover, the planting patterns and root-associated compartments collectively drove the assembly process of root-associated microorganisms. The neutral model showed that, compared with MM, the stochasticity of bacterial assembly decreased under WM and PM but increased for fungal assembly. WM and PM increased the relative effects of the homogenized dispersal of fungal assemblies in roots. We conclude that previous crops exhibit marked legacy effects in the root-associated microbiome. Therefore, soil heritage should not be ignored when discussing microbiome recruitment strategies and co-occurrence patterns in subsequent crops.

Role of the Microbiome in the Diagnosis and Management of Gastroesophageal Cancers

PURPOSE

Stomach and esophageal cancers are among the highest mortality from cancers worldwide. Microbiota has an interplaying role within the human gastrointestinal (GI) tract. Dysbiosis occurs when a disruption of the balance between the microbiota and the host happens. With this narrative review, we discuss the main alterations in the microbiome of gastroesophageal cancer, revealing its potential role in the pathogenesis, early detection, and treatment.

RESULTS

Helicobacter pylori plays a major role the development of a cascade of preneoplastic conditions ranging from atrophic gastritis to metaplasia and dysplasia, ultimately culminating in gastric cancer, while other pathogenic agents are Fusobacterium nucleatum, Bacteroides fragilis, Escherichia coli, and Lactobacillus. Campylobacter species (spp.)'s role in the progression of esophageal adenocarcinoma may parallel that of Helicobacter pylori in the context of gastric cancer, with other esophageal carcinogenic agents being Escherichia coli, Bacteroides fragilis, and Fusobacterium nucleatum. Moreover, gut microbiome could significantly alter the outcomes of chemotherapy and immunotherapy. The gut microbiome can be modulated through interventions such as antibiotics, probiotics, or prebiotics intake. Fecal microbiota transplantation has emerged as a therapeutic strategy as well.

CONCLUSIONS

Nowadays, it is widely accepted that changes in the normal gut microbiome causing dysbiosis and immune dysregulation play a role gastroesophageal cancer. Different interventions, including probiotics and prebiotics intake are being developed to improve therapeutic outcomes and mitigate toxicities associated with anticancer treatment. Further studies are required in order to introduce the microbiome among the available tools of precision medicine in the field of anticancer treatment.

Exploring the Link between Helicobacter pylori, Gastric Microbiota and Gastric Cancer

Gastric cancer (GC) still represents one of the leading causes of cancer-related mortality and is a major public health issue worldwide. Understanding the etiopathogenetic mechanisms behind GC development holds immense potential to revolutionize patients' treatment and prognosis. Within the complex web of genetic predispositions and environmental factors, the connection between Helicobacter pylori (H. pylori) and gastric microbiota emerges as a focus of intense research investigation. According to the most recent hypotheses, H. pylori triggers inflammatory responses and molecular alterations in gastric mucosa, while non-Helicobacter microbiota modulates disease progression. In this review, we analyze the current state of the literature on the relationship between H. pylori and non-Helicobacter gastric microbiota in gastric carcinogenesis, highlighting the mechanisms by which microecological dysbiosis can contribute to the malignant transformation of the mucosa.

Current Knowledge about Gastric Microbiota with Special Emphasis on Helicobacter pylori-Related Gastric Conditions

The gastric milieu, because of its very low acidic pH, is very harsh for bacterial growth. The discovery of Helicobacter pylori (H.p.) has opened a new avenue for studies on the gastric microbiota, thus indicating that the stomach is not a sterile environment. Nowadays, new technologies of bacterial identification have demonstrated the existence of other microorganisms in the gastric habitat, which play an important role in health and disease. This bacterium possesses an arsenal of compounds which enable its survival but, at the same time, damage the gastric mucosa. Toxins, such as cytotoxin-associated gene A, vacuolar cytotoxin A, lipopolysaccharides, and adhesins, determine an inflammatory status of the gastric mucosa which may become chronic, ultimately leading to a gastric carcinoma. In the initial stage, H.p. persistence alters the gastric microbiota with a condition of dysbiosis, predisposing to inflammation. Probiotics and prebiotics exhibit beneficial effects on H.p. infection, and, among them, anti-inflammatory, antioxidant, and antibacterial activities are the major ones. Moreover, the association of probiotics with prebiotics (synbiotics) to conventional anti-H.p. therapy contributes to a more efficacious eradication of the bacterium. Also, polyphenols, largely present in the vegetal kingdom, have been demonstrated to alleviate H.p.-dependent pathologies, even including the inhibition of tumorigenesis. The gastric microbiota composition in health and disease is described. Then, cellular and molecular mechanisms of H.p.-mediated damage are clarified. Finally, the use of probiotics, prebiotics, and polyphenols in experimental models and in patients infected with H.p. is discussed.

Gastric Cancer, Immunotherapy, and Nutrition: The Role of Microbiota

Immune checkpoint inhibitors (ICI) have revolutionized the treatment of gastric cancer (GC), which still represents the third leading cause of cancer-related death in Western countries. However, ICI treatment outcomes vary between individuals and need to be optimized. Recent studies have shown that gut microbiota could represent a key influencer of immunotherapy responses. At the same time, the nutritional status and diet of GC patients are also predictive of immunotherapy treatment response and survival outcomes. The objective of this narrative review is to gather recent findings about the complex relationships between the oral, gastric, and gut bacterial communities, dietary factors/nutritional parameters, and immunotherapy responses. Perigastric/gut microbiota compositions/functions and their metabolites could be predictive of response to immunotherapy in GC patients and even overall survival. At the same time, the strong influence of diet on the composition of the microbiota could have consequences on immunotherapy responses through the impact of muscle mass in GC patients during immunotherapy. Future studies are needed to define more precisely the dietary factors, such as adequate daily intake of prebiotics, that could counteract the dysbiosis of the GC microbiota and the impaired nutritional status, improving the clinical outcomes of GC patients during immunotherapy.

Helicobacter pylori and oral-gut microbiome: clinical implications

More than half of the world's population are colonized with H. pylori; however, the prevalence varies geographically with the highest incidence in Africa. H. pylori is probably a commensal organism that has been associated with the development of gastritis, ulcers, and gastric cancer. H. pylori alone is most probably not enough for the development of gastric carcinoma, but evidence for its association with the disease is high and has, therefore, been classified by the International Agency for Research on Cancer as a Class 1 carcinogen. Bacteroidetes and Fusobacteria positively coexisted during H. pylori infection along the oral-gut axis. The eradication therapy required to treat H. pylori infection can also have detrimental consequences for the gut microbiota, leading to a decreased alpha diversity. Therefore, therapy regimens integrated with probiotics may abolish the negative effects of antibiotic therapy on the gut microbiota. These eradication therapies combined with probiotics have also higher rates of eradication, when compared to standard treatments, and are associated with reduced side effects, improving the patient's compliance. The eradication therapy not only affects gut microbiome but also affects the oral microbiome with robust predominance of harmful bacteria. However, there have been reports of a protective role of H. pylori in Barrett's esophagus, esophageal adenocarcinoma, eosinophilic esophagitis, IBD, asthma, and even multiple sclerosis. Therefore, eradication therapy should be carefully considered, and test to treat policy should be tailored to specific communities especially in highly endemic areas. Supplementation of probiotics, prebiotics, herbals, and microbial metabolites to reduce the negative effects of eradication therapy should be considered. After failure of many eradication attempts, the benefits of H. pylori eradication should be carefully balanced against the risk of adverse effects especially in the elderly, persons with frailty, and intolerance to antibiotics.

The role of the gut microbiome in gastrointestinal cancers

The gut microbiota present in the human digestive system is incredibly varied and is home to trillions of microorganisms. The gut microbiome is shaped at birth, while numerous genetic, dietary, and environmental variables primarily influence the microbiome composition. The importance of gut microbiota on host health is becoming more widely acknowledged. Digestion, intestinal permeability, and immunological and metabolism responses can all be affected by changes in the composition and function of the gut microbiota. There is mounting evidence that the microbial population's complex traits are important biomarkers and indicators of patient outcomes in cancer and its therapies. Numerous studies have demonstrated that changed commensal gut microorganisms contribute to the development and spread of cancer through various routes. Despite the ongoing controversy surrounding the gut microbiome and gastrointestinal cancer, accumulating evidence points to a potentially far more intricate connection than a simple cause-and-effect relationship. SIMPLE SUMMARY: Due to their high frequency and fatality rate, gastrointestinal cancers are regarded as a severe public health issue with complex medical and economic burdens. The gut microbiota may directly or indirectly interact with existing therapies like immunotherapy and chemotherapy, affecting how well a treatment works. The gut microbiome influences the immune response's activity, function, and development. Generally, certain gut bacteria impact the antitumor actions during cancer by creating particular metabolites or triggering T-cell responses. Yet, certain bacterial species have been found to promote cellular proliferation and metastasis in cancer, and comprehending these interactions in the context of cancer may help identify possible treatment targets. Notwithstanding the improvements in the field, additional research is still required to comprehend the underlying processes, examine the effects on existing therapies, and pinpoint certain bacteria and immune cells that can cause this interaction.

Research trends on the relationship between Helicobacter pylori and microbiota: A bibliometric analysis

BACKGROUND

Increasing evidence has indicated that Helicobacter pylori infection is associated with the complex microbiota in the digestive tract of the human body. We aimed to assess the research trends and hotspots in the field of H. pylori and microbiota using a quantitative method.

MATERIALS AND METHODS

The clinical studies on H. pylori and microbiota published from 2001 to 2022 were extracted from the Web of Science database. We visualized and analyzed countries/regions, institutions, authors, journals, and keywords through VOSviewer and CiteSpace software. The test techniques, specimen type, as well as microbiota variation after H. pylori infection and eradication were also evaluated.

RESULTS

A total of 98 publications were finally identified, and the number of annual papers increased gradually. China showed its dominant position in the publication outputs, and Nanchang University was the most productive institution. Cong He, Xu Shu, and Yin Zhu published the highest number of papers, whereas Helicobacter was the most productive journal. "Helicobacter pylori" ranked highest in the keyword occurrences. 16S rRNA gene sequencing was the most frequently used method for microbiota analysis. Fecal samples had the highest frequency of use, followed by gastric mucosa and saliva. H. pylori infection was associated with the alterations of microbiota through the digestive tract, characterized by the enrichment of Helicobacter in the stomach. Triple and quadruple therapy were the most utilized eradication regimens, and probiotics supplementation therapy has been proven to reduce side effects and restore microbial diversity.

CONCLUSIONS

This bibliometric analysis provides an overview of advancements in the field of H. pylori and microbiota. While numerous studies have been conducted on the correlation between H. pylori and the alterations of microbiota, future research is warranted to investigate the mechanisms underlying the interplay between H. pylori and other microbes in the development of related diseases.

The Gut Microbiota: a Novel Player in the Pathogenesis of Uterine Fibroids

Uterine fibroid is a common gynecological disorder that affects women of reproductive age and has emerged as a major public health concern. The symptoms have a negative influence on both their physical health and quality of life. The cost of treatment has a significant impact on the disease's burden. Even though its origin is uncertain, estrogen is thought to be a key player in fibroid pathophysiology. Many theories, including those based on genetic and environmental factors, explain what causes hyper-estrogenic condition in fibroid patients. One such possibility that is currently being explored is the hypothesis that an altered gut microbiome can contribute to the development of diseases characterized by estrogen dominance. Gut dysbiosis is often a "hot area" in the health sciences. According to a recent study, uterine fibroid patients have altered gut microbiome. A variety of risk factors influence both fibroid development and gut homeostasis. Diet, lifestyle, physical activity, and environmental contaminants have an impact on estrogen and the gut flora. A better understanding of uterine fibroids' pathophysiology is required to develop effective preventative and treatment options. A few ways by which the gut microbiota contributes to UF include estrogen, impaired immune function, inflammation, and altered gut metabolites. Therefore, in the future, while treating fibroid patients, various strategies to deal with changes in the gut flora may be advantageous. For developing suggestions for clinical diagnosis and therapy, we reviewed the literature on the relationship between uterine fibroids and the gut microbiota.

Diversification and deleterious role of microbiome in gastric cancer

Gut microbiota dictates the fate of several diseases, including cancer. Most gastric cancers (GC) belong to gastric adenocarcinomas (GAC). Helicobacter pylori colonizes the gastric epithelium and is the causative agent of 75% of all stomach malignancies globally. This bacterium has several virulence factors, including cytotoxin-associated gene A (CagA), vacuolating cytotoxin (VacA), and outer membrane proteins (OMPs), all of which have been linked to the development of gastric cancer. In addition, bacteria such as Escherichia coli, Streptococcus, Clostridium, Haemophilus, Veillonella, Staphylococcus, and Lactobacillus play an important role in the development of gastric cancer. Besides, lactic acid bacteria (LAB) such as Bifidobacterium, Lactobacillus, Lactococcus, and Streptococcus were found in greater abundance in GAC patients. To identify potential diagnostic and therapeutic interventions for GC, it is essential to understand the mechanistic role of H. pylori and other bacteria that contribute to gastric carcinogenesis. Furthermore, understanding bacteria-host interactions and bacteria-induced inflammatory pathways in the host is critical for developing treatment targets for gastric cancer.

Role of the intratumoral microbiome in tumor progression and therapeutics implications

Microbes are widely present in various organs of the human body and play important roles in numerous physiological and pathological processes. Nevertheless, owing to multiple limiting factors, such as contamination and low biomass, the current understanding of the intratumoral microbiome is limited. The intratumoral microbiome exerts tumor-promoting or tumor-suppressive effects by engaging in metabolic reactions within the body, regulating signaling cancer-related pathways, and impacting both host cells function and immune system. It is important to emphasize that intratumoral microbes exhibit substantial heterogeneity in terms of composition and abundance across various tumor types, thereby potentially influencing diverse aspects of tumorigenesis, progression, and metastasis. These findings suggest that intratumoral microbiome have great potential as diagnostic and prognostic biomarkers. By manipulating the intratumoral microbes to employ cancer therapy, the efficacy of chemotherapy or immunotherapy can be enhanced while minimizing adverse effects. In this review, we comprehensively describe the composition and function of the intratumoral microbiome in various human solid tumors. Combining recent advancements in research, we discuss the origins, mechanisms, and prospects of the clinical applications of intratumoral microbiome.

Crosstalk between Helicobacter pylori and gastrointestinal microbiota in various gastroduodenal diseases-A systematic review

Gastroduodenal diseases have prevailed for a long time and more so due to dominance of gut bacteria Helicobacter pylori in most of the cases. But habitation by other gut microbiota in gastroduodenal diseases and the relationship between Helicobacter pylori and gastrointestinal microbiota in different gastroduodenal diseases is somewhat being unravelled in the current times. For this systematic review, we did a literature search of various gastroduodenal diseases and the effect on gut microbiota pertaining to it. A search of the online bibliographic databases PUBMED and PUBMED CENTRAL was carried out to identify articles published between 1977 and May 2022. The analysis of these selected studies highlighted the inhabitation of other gut microbiota such as Fusobacteria, Bacteroidetes, Streptococcaceae, Prevotellaceae, Fusobacteriaceae, and many others. Interplay between these microbiota and H. pylori have also been noted which suggested that gastroduodenal diseases and gut microbiota are intertwined by a symbiotic association regardless of the H. pylori status. The relationship between the gut microbiota and many gastroduodenal diseases, such as gastritis, gastric cancer, lymphomas, and ulcers, demonstrates the dysbiosis of the gut microbiota in both the presence and absence of H. pylori. The evolving ways for eliminating H. pylori are provided along with inhibiting qualities of other species on H. pylori. Most significant member of our gut system is Helicobacter pylori which has been associated with numerous diseases like gastric cancer, gastritis, duodenal ulcer.

Association of dietary inflammatory index with helicobacter pylori infection and mortality among US population

BACKGROUND

Limited research has been conducted on the potential relationship between the dietary inflammation index (DII) and mortality, particularly in individuals with Helicobacter pylori (H. pylori) infection. This study aimed to investigate the association between the DII and H. pylori infection, as well as their respective impacts on all-cause mortality in a cohort of individuals with or without H. pylori infection.

METHODS

Data from the 1999-2018 National Health and Nutrition Examination Survey (NHANES) were utilized for this study, with a final of 4370 participants included. Both univariable and multivariable-adjusted logistic regression analyses were employed to explore the relationship between H. pylori infection and pertinent covariates. Cox regression analysis, as well as restricted regression cubic spline analysis, were utilized to assess the association between DII and all-cause mortality among individuals with or without H. pylori infection.

RESULTS

The findings demonstrated a positive correlation between DII scores and H. pylori infection, even after adjusting for potential confounding factors. Moreover, higher DII scores were significantly associated with an elevated risk of mortality exclusively in individuals with H. pylori infection, while no such association was observed in the uninfected population. Additional analysis using restricted cubic spline modeling revealed a positive linear relationship between DII scores as a continuous variable and the adjusted risk of all-cause mortality specifically in H. pylori-infected patients.

CONCLUSION

The results of this study indicated that DII was positively correlated with an increased risk of H. pylori infection and was associated with a heightened risk of all-cause mortality solely in individuals with H. pylori infection. Consequently, DII might serve as a useful tool for risk stratification in the H. pylori-infected population among U.S. adults. Further research is warranted to elucidate the underlying mechanisms and potential clinical implications of these findings.

The role of gastric microecological dysbiosis in gastric carcinogenesis

Gastric cancer (GC) is the leading cause of cancer-related death worldwide, and reducing its mortality has become an urgent public health issue. Gastric microecological dysbiosis (including bacteria, fungi, viruses, acid suppressants, antibiotics, and surgery) can lead to gastric immune dysfunction or result in a decrease in dominant bacteria and an increase in the number and virulence of pathogenic microorganisms, which in turn promotes development of GC. This review analyzes the relationship between gastric microecological dysbiosis and GC, elucidates dynamic alterations of the microbiota in Correa's cascade, and identifies certain specific microorganisms as potential biomarkers of GC to aid in early screening and diagnosis. In addition, this paper presents the potential of gastric microbiota transplantation as a therapeutic target for gastric cancer, providing a new direction for future research in this field.

The role of the gut microbiota in gastric cancer: the immunoregulation and immunotherapy

Gastric cancer (GC) is one of the most common cancers, leading to the deaths of millions of people worldwide. Therefore, early detection and effective therapeutic strategies are of great value for decreasing the occurrence of advanced GC. The human microbiota is involved not only in the maintenance of physiological conditions, but also in human diseases such as obesity, diabetes, allergic and atopic diseases, and cancer. Currently, the composition of the bacteria in the host, their functions, and their influence on disease progression and treatment are being discussed. Previous studies on the gut microbiome have mostly focused on Helicobacter pylori (Hp) owing to its significant role in the development of GC. Nevertheless, the enrichment and diversity of other bacteria that can modulate the tumor microenvironment are involved in the progression of GC and the efficacy of immunotherapy. This review provides systematic insight into the components of the gut microbiota and their application in GC, including the specific bacteria of GC, their immunoregulatory effect, and their diagnostic value. Furthermore, we discuss the relationship between the metabolism of microbes and their potential applications, which may serve as a new approach for the diagnosis and treatment of GC.

Impact of Helicobacter pylori infection on the efficacy of immune checkpoint inhibitors for cancer treatment: a meta-analysis

Aim: The present systematic review and meta-analysis was designed to assess the impact of Helicobacter pylori infection on the efficacy of immune checkpoint inhibitors (ICIs). Materials & methods: PubMed, Scopus, Web of Science and EMBASE databases were systematically searched up to 1 February 2023. Results: Three studies comprising 263 patients treated with ICIs were included. The results of pooled analysis showed that H. pylori infection was associated with reduced overall survival and progression-free survival. Furthermore, the rate of progressive disease after administration of ICIs was higher in H. pylori-positive patients relative to H. pylori-negative patients. Conclusion: H. pylori infection status is a novel potential response biomarker for predicting the efficacy of ICIs in different cancers.

Gastric microbiota: an emerging player in gastric cancer

Gastric cancer (GC) is a common cancer worldwide with a high mortality rate. Many microbial factors influence GC, of which the most widely accepted one is Helicobacter pylori (H. pylori) infection. H. pylori causes inflammation, immune reactions and activation of multiple signaling pathways, leading to acid deficiency, epithelial atrophy, dysplasia and ultimately GC. It has been proved that complex microbial populations exist in the human stomach. H. pylori can affect the abundance and diversity of other bacteria. The interactions among gastric microbiota are collectively implicated in the onset of GC. Certain intervention strategies may regulate gastric homeostasis and mitigate gastric disorders. Probiotics, dietary fiber, and microbiota transplantation can potentially restore healthy microbiota. In this review, we elucidate the specific role of the gastric microbiota in GC and hope these data can facilitate the development of effective prevention and therapeutic approaches for GC.

The Influence of Helicobacter pylori on Human Gastric and Gut Microbiota

Helicobacter pylori is a Gram-negative bacterium that is able to colonize the human stomach, whose high prevalence has a major impact on human health, due to its association with several gastric and extra-gastric disorders, including gastric cancer. The gastric microenvironment is deeply affected by H. pylori colonization, with consequent effects on the gastrointestinal microbiota, exerted via the regulation of various factors, including gastric acidity, host immune responses, antimicrobial peptides, and virulence factors. The eradication therapy required to treat H. pylori infection can also have detrimental consequences for the gut microbiota, leading to a decreased alpha diversity. Notably, therapy regimens integrated with probiotics have been shown to reduce the negative effects of antibiotic therapy on the gut microbiota. These eradication therapies combined with probiotics have also higher rates of eradication, when compared to standard treatments, and are associated with reduced side effects, improving the patient's compliance. In light of the deep impact of gut microbiota alterations on human health, the present article aims to provide an overview of the complex interaction between H. pylori and the gastrointestinal microbiota, focusing also on the consequences of eradication therapies and the effects of probiotic supplementation.

Microbiome and function alterations in the gastric mucosa of asymptomatic patients with Helicobacter pylori infection

BACKGROUND

Most patients with Helicobacter pylori (H. pylori) infection have no clinical symptoms, numerous studies reported the gastric microbiome in H. pylori-infected patients, but asymptomatic patients have not been distinguished. How the microbiome and function changes in asymptomatic patients with H. pylori infection remains poorly understood.

METHODS

A total of 29 patients were divided into H. pylori-infected asymptomatic group (10 patients), H. pylori-infected symptomatic group (11 patients) and H. pylori-uninfected group (8 patients). Gastric mucosa specimens were taken for histopathological examination, special staining, and 16 S rDNA sequencing. High-throughput results were evaluated by community composition analysis, indicator species analysis, alpha diversity analysis, beta diversity analysis, and function prediction.

RESULTS

The gastric microbiota composition at phylum and genus level of H. pylori-infected asymptomatic patients were similar with H. pylori-infected symptomatic group, but different from H. pylori-uninfected patients. The diversity and richness of gastric microbial community declined significantly in H. pylori-infected asymptomatic group comparing with H. pylori-uninfected group. Sphingomonas may be an indicator between symptomatic and asymptomatic patients with H. pylori infection, the AUC value of Sphingomonas is 0.79. Interactions between species increased and altered notably after H. pylori infection. More genera were affected by Helicobacter in H. pylori-infected asymptomatic patients. The function condition changed significantly in asymptomatic patients with H. pylori infection, there was no difference comparing with symptomatic ones. Amino acid metabolism and lipid metabolism strengthened but carbohydrate metabolism remained constant after H. pylori infection. The metabolism of fatty acid and bile acid was disturbed after infection with H. pylori.

CONCLUSION

The gastric microbiota composition and function mode changed significantly after H. pylori infection regardless of the presence of clinical symptoms, there was no difference between H. pylori-infected asymptomatic and symptomatic patients. The difference in gastric microbiota composition and interactions between species might be responsible for presence of digestive symptoms.

Bacterial Infections and Cancer: Exploring This Association And Its Implications for Cancer Patients

Bacterial infections are common in the etiology of human diseases owing to the ubiquity of bacteria. Such infections promote the development of periodontal disease, bacterial pneumonia, typhoid, acute gastroenteritis, and diarrhea in susceptible hosts. These diseases may be resolved using antibiotics/antimicrobial therapy in some hosts. However, other hosts may be unable to eliminate the bacteria, allowing them to persist for long durations and significantly increasing the carrier's risk of developing cancer over time. Indeed, infectious pathogens are modifiable cancer risk factors, and through this comprehensive review, we highlight the complex relationship between bacterial infections and the development of several cancer types. For this review, searches were performed on the PubMed, Embase, and Web of Science databases encompassing the entirety of 2022. Based on our investigation, we found several critical associations, of which some are causative: Porphyromonas gingivalis and Fusobacterium nucleatum are associated with periodontal disease, Salmonella spp., Clostridium perfringens, Escherichia coli, Campylobacter spp., and Shigella are associated with gastroenteritis. Helicobacter pylori infection is implicated in the etiology of gastric cancer, and persistent Chlamydia infections present a risk factor for the development of cervical carcinoma, especially in patients with the human papillomavirus (HPV) coinfection. Salmonella typhi infections are linked with gallbladder cancer, and Chlamydia pneumoniae infection is implicated in lung cancer, etc. This knowledge helps identify the adaptation strategies used by bacteria to evade antibiotic/antimicrobial therapy. The article also sheds light on the role of antibiotics in cancer treatment, the consequences of their use, and strategies for limiting antibiotic resistance. Finally, the dual role of bacteria in cancer development as well as in cancer therapy is briefly discussed, as this is an area that may help to facilitate the development of novel microbe-based therapeutics as a means of securing improved outcomes.

Gut Microbiota in Colorectal Cancer: Biological Role and Therapeutic Opportunities

Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths worldwide. While CRC is thought to be an interplay between genetic and environmental factors, several lines of evidence suggest the involvement of gut microbiota in promoting inflammation and tumor progression. Gut microbiota refer to the ~40 trillion microorganisms that inhabit the human gut. Advances in next-generation sequencing technologies and metagenomics have provided new insights into the gut microbial ecology and have helped in linking gut microbiota to CRC. Many studies carried out in humans and animal models have emphasized the role of certain gut bacteria, such as Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, and colibactin-producing Escherichia coli, in the onset and progression of CRC. Metagenomic studies have opened up new avenues for the application of gut microbiota in the diagnosis, prevention, and treatment of CRC. This review article summarizes the role of gut microbiota in CRC development and its use as a biomarker to predict the disease and its potential therapeutic applications.

Helicobacter pylori and gastric microbiota homeostasis: progress and prospects

Helicobacter pylori, a Gram-negative microaerobic bacteria belonging to the phylum Proteobacteria, can colonize in the stomach and duodenum, and cause a series of gastrointestinal diseases such as gastritis, gastric ulcer and even gastric cancer. At present, the high diversity of the microorganisms in the stomach has been confirmed with culture-independent methods; some researchers have also studied the stomach microbiota composition at different stages of H. pylori carcinogenesis. Here, we mainly review the possible role of H. pylori-mediated microbiota changes in the occurrence and development of gastric cancer to provide new ideas for preventing H. pylori infection and regulating microecological imbalance.

Gastric microbiome changes in relation with Helicobacter pylori resistance

INTRODUCTION

Inadequate antimicrobial treatment has led to multidrug-resistant (MDR) bacteria, including Helicobacter pylori (H. pylori), which one of the notable pathogens in the stomach. Antibiotic-induced changes in the microbiota can negatively affect the host. This study aimed to determine the influence of H. pylori resistance on the diversity and abundance of the stomach microbiome.

METHODS

Bacterial DNA was extracted from biopsy samples of patients presenting dyspepsia symptoms with H. pylori positive from cultures and histology. DNA was amplified from the V3-V4 regions of the 16S rRNA gene. In-vitro E-test was used to detect antibiotic resistance. Microbiome community analysis was conducted through α-diversity, β-diversity, and relative abundance.

RESULTS

Sixty-nine H. pylori positive samples were eligible after quality filtering. Following resistance status to five antibiotics, samples were classified into 24 sensitive, 24 single resistance, 16 double resistance, 5 triple resistance. Samples were mostly resistant to metronidazole (73.33%; 33/45). Comparation of four groups displayed significantly elevated α-diversity parameters under the multidrug resistance condition (all P <0.05). A notable change was observed in triple-resistant compared to sensitive (P <0.05) and double-resistant (P <0.05) groups. Differences in β-diversity by UniFrac and Jaccard were not significant in terms of the resistance (P = 0.113 and P = 0.275, respectively). In the triple-resistant group, the relative abundance of Helicobacter genera was lower, whereas that of Streptococcus increased. Moreover, the linear discriminant analysis effect size (LEfSe) was associated with the presence of Corynebacterium and Saccharimonadales in the single-resistant group and Pseudomonas and Cloacibacterium in the triple-resistant group.

CONCLUSION

Our results suggest that the resistant samples showed a higher trend of diversity and evenness than the sensitive samples. The abundance of H. pylori in the triple-resistant samples decreased with increasing cohabitation of pathogenic bacteria, which may support antimicrobial resistance. However, antibiotic susceptibility determined by the E-test may not completely represent the resistance status.

Protective immunity enhanced Salmonella vaccine vectors delivering Helicobacter pylori antigens reduce H. pylori stomach colonization in mice

Helicobacter pylori is a major cause of gastric mucosal inflammation, peptic ulcers, and gastric cancer. Emerging antimicrobial-resistant H. pylori has hampered the effective eradication of frequent chronic infections. Moreover, a safe vaccine is highly demanded due to the absence of effective vaccines against H. pylori. In this study, we employed a new innovative Protective Immunity Enhanced Salmonella Vaccine (PIESV) vector strain to deliver and express multiple H. pylori antigen genes. Immunization of mice with our vaccine delivering the HpaA, Hp-NAP, UreA and UreB antigens, provided sterile protection against H. pylori SS1 infection in 7 out of 10 tested mice. In comparison to the control groups that had received PBS or a PIESV carrying an empty vector, immunized mice exhibited specific and significant cellular recall responses and antigen-specific serum IgG1, IgG2c, total IgG and gastric IgA antibody titers. In conclusion, an improved S. Typhimurium-based live vaccine delivering four antigens shows promise as a safe and effective vaccine against H. pylori infection.

Role of the duodenal microbiota in functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a common and debilitating gastrointestinal disorder attributed to altered gut-brain interactions. While the etiology of FD remains unknown, emerging research suggests the mechanisms are likely multifactorial and heterogenous among patient subgroups. Small bowel motor disturbances, visceral hypersensitivity, chronic microinflammation, and increased intestinal tract permeability have all been linked to the pathogenesis of FD. Recently, alterations to the gut microbiome have also been implicated to play an important role in the disease. Changes to the duodenal microbiota may either trigger or be a consequence of immune and neuronal disturbances observed in the disease, but the mechanisms of influence of small intestinal flora on gastrointestinal function and symptomatology are unknown.

PURPOSE

This review summarizes and synthesizes the literature on the link between the microbiota, low-grade inflammatory changes in the duodenum and FD. This review is not intended to provide a complete overview of FD or the small intestinal microbiota, but instead outline some of the key conceptual advances in understanding the interactions between altered gastrointestinal bacterial communities; dietary factors; host immune activation; and stimulation of the gut-brain axes in patients with FD versus controls. Current and emerging treatment approaches such as dietary interventions and antibiotic or probiotic use that have demonstrated symptom benefits for patients are reviewed, and their role in modulating the host-microbiota is discussed. Finally, suggested opportunities for diagnostic and therapeutic improvements for patients with this condition are presented.

A literature review on the potential clinical implications of streptococci in gastric cancer

Streptococcus is widely found in nature and the human body, and most species are not pathogenic. In recent years, studies have found that Streptococcus is associated with gastric cancer. Streptococcus was found to be enriched in the oral cavity, stomach and intestine of gastric cancer patients and found to be increased in gastric cancer tissues, suggesting that Streptococcus may be the pathogenic bacteria underlying gastric cancer. This review discusses the discovery of Streptococcus, the relationship between Streptococcus and gastric cancer, and the possible carcinogenic mechanism of Streptococcus and summarizes the progress of the research on the role of Streptococcus in gastric cancer to provide new ideas for the early detection, diagnosis and treatment of gastric cancer.

Effects of Helicobacter pylori Therapy on Gut Microbiota: A Systematic Review and Meta-Analysis

BACKGROUND

Although indications for evaluation and treatment of Helicobacter pylori infection are broadening to include primary prevention for gastric adenocarcinoma, potential adverse effects on gut microbiota have been raised. We performed a systematic review and meta-analysis to evaluate the effects of H. pylori therapy on gut microbiota.

METHODS

PubMed, EMBASE, Cochrane Library, and Web of Science (to 4/2021) were searched for studies quantitatively evaluating microbiota before and after H. pylori therapy. Meta-analysis was performed to assess early (<1 year) and long-term (≥1 year) effects on gut microbiota after H. pylori treatment. Subgroup analysis evaluating the effects of H. pylori therapy with addition of probiotics on gut microbiota was also performed.

RESULTS

Thirty studies (N = 1,218) met the criteria. Early after H. pylori therapy, intestinal microbial diversity was reduced in nearly all studies. At the genus level, reduction in the abundance of Enterococcus, while increase in Lactobacillus, Bifidobacterium, and Bacteroides counts were observed. However, Enterococcus, Lactobacillus, Bifidobacterium, and Bacteroides counts remained stable in patients who received probiotics with H. pylori therapy. At the phylum level, the relative abundance of Actinobacteria and Firmicutes increased after treatment. At ≥1 year, intestinal microbial diversity normalized in six of seven studies. No differences in the relative abundance of Actinobacteria, Firmicute, Bacteroidetes, and Proteobacteria were observed ≥1 year after therapy.

CONCLUSION

The impact of H. pylori therapy on gut microbiota appears transient with early changes largely resolving after 1 year. Probiotics may reduce the early impact of H. pylori therapy on gut microbiota.

Urolithin A Attenuates Helicobacter pylori-Induced Damage In Vivo

Urolithin A (UA) is a metabolite produced in the gut following the consumption of ellagic acid (EA) rich foods. EA has shown anti-inflammatory, antioxidant, and anticancer properties. Because EA is poorly absorbed in the gastrointestinal tract, urolithins are considered to play a major role in bioactivity. Helicobacter pylori (H. pylori) infection is the most common chronic bacterial infection all over the world. It is potentially hazardous to humans because of its relationship to various gastrointestinal diseases. In this study, we investigated the effect of UA on inflammation by H. pylori. The results indicated that UA attenuated H. pylori-induced inflammation in vitro and in vivo. UA also reduced the secretion of H. pylori virulence factors and tissue injuries in mice. Furthermore, UA decreased the relative abundance of Helicobacteraceae in feces of H. pylori-infected mice. In summary, taking UA effectively inhibited the injury caused by H. pylori.

Refractory Helicobacter pylori infection and the gastric microbiota

Background

Curing refractory Helicobacter pylori infection is difficult. In addition, there is currently no research on the gastric microbiota of refractory H. pylori infection.

Methods

We designed a clinical retrospective study involving 32 subjects divided into three groups: 1. nAGHp.a, treatment-naïve patients with H. pylori infection; 2. nAGHp.b, H. pylori-negative patients; and 3. EFHp.a, patients with refractory H. pylori infection. Gastric mucosal samples from the biobank of our research center were collected for 16S rRNA sequencing analysis and bacterial functions were predicted via PICRUSt.

Results

There were significant differences between the H. pylori- positive group and the H. pylori-negative group in species diversity, gastric microbiota structure, and bacterial function. The beneficial Lactobacillus in the H. pylori-positive group were significantly enriched compared with those in the refractory H. pylori infection group. The bacterial interaction network diagram suggested that the microbiota interactions in the refractory H. pylori infection group decreased. The gastric microbiota of the refractory H. pylori infection group was enriched in the pathways of metabolism and infectious diseases (energy metabolism, bacterial secretion system, glutathione metabolism, protein folding and associated processing, sulphur metabolism, membrane and intracellular structural molecules, lipopolysaccharide biosynthesis, ubiquinone and other terpenoid-quinone biosynthesis, inorganic ion transport and metabolism, and metabolism of cofactors and vitamins) when compared with the H. pylori-positive group without treatment based on PICRUSt analysis.

Conclusion

Significant alterations occurred in the gastric microbiota when eradication of H. pylori failed multiple times. A history of eradication of multiple H. pylori infections leads to an imbalance in the gastric mucosal microbiota to a certain extent, which was mainly reflected in the inhibition of the growth of beneficial Lactobacillus in the stomach. Patients with refractory H. pylori infection may be at a higher risk of developing gastric cancer than other H. pylori-positive patients.

Alterations in the gastric microbiota and metabolites in gastric cancer: An update review

Gastric cancer (GC) is one of the leading causes of cancer mortality worldwide. Numerous studies have shown that the gastric microbiota can contribute to the occurrence and development of GC by generating harmful microbial metabolites, suggesting the possibility of discovering biomarkers. Metabolomics has emerged as an advanced promising analytical method for the analysis of microbiota-derived metabolites, which have greatly accelerated our understanding of host-microbiota metabolic interactions in GC. In this review, we briefly compiled recent research progress on the changes of gastric microbiota and its metabolites associated with GC. And we further explored the application of metabolomics and gastric microbiome association analysis in the diagnosis, prevention and treatment of GC.

Association of Helicobacter pylori infection with survival outcomes in advanced gastric cancer patients treated with immune checkpoint inhibitors

Background

Accumulating evidence has revealed that the gut microbiota influences the effectiveness of immune checkpoint inhibitors (ICIs) in cancer patients. As a part of the human microbiome, Helicobacter pylori (H. pylori) was reported to be associated with reduced effectiveness of anti-PD1 immunotherapy in patients with non-small-cell lung cancer (NSCLC). Gastric cancer is more closely related to H. pylori, so we conducted a retrospective analysis to verify whether the association of H. pylori and effectiveness is applicable to advanced gastric cancer (AGC) patients.

Material and methods

AGC patients who had evidence of H. pylori and received anti-PD-1 antibodies were enrolled in the study. The differences in the disease control rate (DCR), overall survival (OS) and progression-free survival (PFS) between the H. pylori-positive group and the negative group were compared.

Results

A total of 77 patients were included in this study; 34 patients were H. pylori positive, and the prevalence of H. pylori infection was 44.2%. Compared with the H. pylori-negative group, patients in the H. pylori-positive group had a higher risk of nonclinical response to anti-PD-1 antibody, with an OR of 2.91 (95% CI: 1.13–7.50). Patients in the H. pylori-negative group had a longer OS and PFS than those in the positive group, with an estimated median OS of 17.5 months vs. 6.2 months (HR = 2.85, 95% CI: 1.70–4.78; P = 0.021) and a median PFS of 8.4 months vs. 2.7 months (HR = 3.11, 95% CI: 1.96–5.07, P = 0.008). Multivariate analysis indicated that H. pylori infection was independently associated with PFS (HR = 1.90, 95% CI: 1.10–3.30; P = 0.022).

Conclusion

Our study unveils for the first time that H. pylori infection is associated with the outcome of immunotherapy for AGC patients. Multicenter, large sample and prospective clinical studies are needed to verify the association.

The interplay between Helicobacter pylori and the gut microbiota: An emerging driver influencing the immune system homeostasis and gastric carcinogenesis

The human gut microbiota are critical for preserving the health status because they are required for digestion and nutrient acquisition, the development of the immune system, and energy metabolism. The gut microbial composition is greatly influenced by the colonization of the recalcitrant pathogen Helicobacter pylori (H. pylori) and the conventional antibiotic regimens that follow. H. pylori is considered to be the main microorganism in gastric carcinogenesis, and it appears to be required for the early stages of the process. However, a non-H. pylori microbiota profile is also suggested, primarily in the later stages of tumorigenesis. On the other hand, specific groups of gut microbes may produce beneficial byproducts such as short-chain fatty acids (acetate, butyrate, and propionate) that can modulate inflammation and tumorigenesis pathways. In this review, we aim to present how H. pylori influences the population of the gut microbiota to modify the host immunity and trigger the development of gastric carcinogenesis. We will also highlight the effect of the gut microbiota on immunotherapeutic approaches such as immune checkpoint blockade in cancer treatment to present a perspective for further development of innovative therapeutic paradigms to prevent the progression of H. pylori-induced stomach cancer.

Influences of Helicobacter pylori infection on diversity, heterogeneity, and composition of human gastric microbiomes across stages of gastric cancer development

BACKGROUND

About a half of the world's population is infected with Helicobacter pylori (H. pylori), but only 1%-3% of them develop gastric cancer. As a primary risk factor for gastric cancer, the relationship between H. pylori infection and gastric microbiome has been a focus in recent years.

MATERIALS AND METHODS

We reanalyze 11 human gastric microbiome datasets with or without H. pylori, covering the healthy control (HC) and four disease stages (chronic gastritis (CG), atrophic gastritis (AG), intestinal metaplasia (IM), and gastric cancer (GC)) of gastric cancer development to quantitatively compare the influences of the H. pylori infection and disease stages on the diversity, heterogeneity, and composition of gastric microbiome. Four medical ecology approaches including (i) diversity analysis with Hill numbers, (ii) heterogeneity analysis with Taylor's power law extensions (TPLE), (iii) diversity scaling analysis with diversity-area relationship (DAR) model, and (iv) shared species analysis were applied to fulfill the data reanalysis.

RESULTS

(i) The influences of H. pylori infection on the species diversity, spatial heterogeneity, and potential diversity of gastric microbiome seem to be more prevalent than the influences of disease stages during gastric cancer development. (ii) The influences of H. pyloriinfection on diversity, heterogeneity, and composition of gastric microbiomes in HC, CG, IM, and GC stages appear more prevalent than those in AG stage.

CONCLUSION

Our study confirmed the impact of H. pylori infection on human gastric microbiomes: The influences of H. pylori infection on the diversity, heterogeneity, and composition of gastric microbiomes appear to be disease-stage dependent.

A complete guide to human microbiomes: Body niches, transmission, development, dysbiosis, and restoration

Humans are supra-organisms co-evolved with microbial communities (Prokaryotic and Eukaryotic), named the microbiome. These microbiomes supply essential ecosystem services that play critical roles in human health. A loss of indigenous microbes through modern lifestyles leads to microbial extinctions, associated with many diseases and epidemics. This narrative review conforms a complete guide to the human holobiont-comprising the host and all its symbiont populations- summarizes the latest and most significant research findings in human microbiome. It pretends to be a comprehensive resource in the field, describing all human body niches and their dominant microbial taxa while discussing common perturbations on microbial homeostasis, impacts of urbanization and restoration and humanitarian efforts to preserve good microbes from extinction.

Microbial Diversity and Composition in Six Different Gastrointestinal Sites among Participants Undergoing Upper Gastrointestinal Endoscopy in Henan, China

The objective of this study was to describe and compare the dynamic microbiota characteristics in the gastrointestinal (GI) tract in Chinese participants via high-throughput sequencing techniques. The study collected saliva, esophageal swab, cardia biopsy, noncardia biopsy, gastric juice, and fecal specimens from 40 participants who underwent upper GI tract cancer screening in Linzhou (Henan, China) in August 2019. The V4 region of 16S rRNA genes was amplified and sequenced using the Illumina MiniSeq platform. The observed amplicon sequence variants (ASVs) gradually decreased from saliva to esophageal swab, cardia biopsy, noncardia biopsy, and gastric juice specimens and then increased from gastric juice to fecal specimens (P < 0.05). Each GI site had its own microbial characteristics that overlapped those of adjacent sites. Characteristic genera for each site were as follows: Neisseria and Prevotella in saliva, Streptococcus and Haemophilus in the esophagus, Helicobacter in the noncardia, Pseudomonas in gastric juice, Faecalibacterium, Roseburia, and Blautia in feces, and Weissella in the cardia. Helicobacter pylori-positive participants had decreased observed ASVs (cardia, P < 0.01; noncardia, P < 0.001) and Shannon index values (cardia, P < 0.001; noncardia, P < 0.001) compared with H. pylori-negative participants both in cardia and noncardia specimens. H. pylori infection played a more important role in the microbial composition of noncardia than of cardia specimens. In gastric juice, the gastric pH and H. pylori infection had similar additive effects on the microbial diversity and composition. These results show that each GI site has its own microbial characteristics that overlap those of adjacent sites and that differences and commonalities between and within microbial compositions coexist, providing essential foundations for the continuing exploration of disease-associated microbiota. IMPORTANCE Upper gastrointestinal (UGI) tract cancer is one of the most common cancers worldwide, while limited attention has been paid to the UGI microbiota. Microbial biomarkers, such as Fusobacteria nucleatum and Helicobacter pylori, bring new ideas for early detection of UGI tract cancer, which may be a highly feasible method to reduce its disease burden. This study revealed that each gastrointestinal site had its own microbial characteristics that overlapped those of adjacent sites. There were significant differences between the microbial compositions of the UGI sites and feces. Helicobacter pylori played a more significant role in the microbial composition of the noncardia stomach than in that of the cardia. Gastric pH and Helicobacter pylori had similar additive effects on the microbial diversity of gastric juice. These findings played a key role in delineating the microbiology spectrum of the gastrointestinal tract and provided baseline information for future microbial exploration covering etiology, primary screening, treatment, outcome, and health care products.

Helicobacter pylori, gastric microbiota and gastric cancer relationship: Unrolling the tangle

Helicobacter pylori infection (Hp-I) represents a typical microbial agent intervening in the complex mechanisms of gastric homeostasis by disturbing the balance between the host gastric microbiota and mucosa-related factors, leading to inflammatory changes, dysbiosis and eventually gastric cancer. The normal gastric microbiota shows diversity, with Proteobacteria [Helicobacter pylori (H. pylori) belongs to this family], Firmicutes, Actinobacteria, Bacteroides and Fusobacteria being the most abundant phyla. Most studies indicate that H. pylori has inhibitory effects on the colonization of other bacteria, harboring a lower diversity of them in the stomach. When comparing the healthy with the diseased stomach, there is a change in the composition of the gastric microbiome with increasing abundance of H. pylori (where present) in the gastritis stage, while as the gastric carcinogenesis cascade progresses to gastric cancer, the oral and intestinal-type pathogenic microbial strains predominate. Hp-I creates a premalignant environment of atrophy and intestinal metaplasia and the subsequent alteration in gastric microbiota seems to play a crucial role in gastric tumorigenesis itself. Successful H. pylori eradication is suggested to restore gastric microbiota, at least in primary stages. It is more than clear that Hp-I, gastric microbiota and gastric cancer constitute a challenging tangle and the strong interaction between them makes it difficult to unroll. Future studies are considered of crucial importance to test the complex interaction on the modulation of the gastric microbiota by H. pylori as well as on the relationships between the gastric microbiota and gastric carcinogenesis.

Helicobacter Species and Their Association with Gastric Pathology in a Cohort of Dogs with Chronic Gastrointestinal Signs

Prevalence of individual Helicobacter species, data evaluating their association with gastric pathology and comparison of accuracy of diagnostic techniques are limited. The aims of this study were to determine the prevalence of gastric Helicobacter species, their association with gastric pathology, and to compare diagnostic techniques. Gastric biopsies from 84 privately-owned dogs with chronic gastrointestinal signs were obtained endoscopically. Helicobacters were detected using PCR, cytology, urease test, and histopathology. PCR detected helicobacters in 71.4% of dogs. Helicobacter heilmannii sensu stricto (s.s.) was the predominant species. Mixed infection was detected in 40% of PCR positive dogs. Gastritis was diagnosed in 38.5% of Helicobacter positive and 47.4% of Helicobacter negative dogs. Mono-infection was associated with 2.4 times increased odds of having more severe inflammation compared to mixed infection. Erosions and ulcers were common endoscopic lesions. Cytology had sensitivity/specificity of 88.3/91.7%. Association between infection and lymphoid follicular hyperplasia was demonstrated.

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.

Helicobacter pylori infection affects the human gastric microbiome, as revealed by metagenomic sequencing

Helicobacter pylori infection is a prevalent infectious disease, associated with many gastric diseases, including gastritis, gastric ulcer, and gastric cancer. To reveal the characteristics of the gastric microbiome in patients infected with H. pylori, we performed metagenomic shotgun sequencing of stomach swab samples from 96 patients and then conducted metagenomic association analyses between alterations in the gastric microbiome and H. pylori infection status. The overall composition of the gastric microbiota in H. pylori‐infected individuals was distinctly different from the negative controls; H. pylori became the dominant species after colonizing the human stomach and significantly decreased the α‐diversity of the gastric community (P < 0.05, Wilcoxon rank‐sum test). We also identified 6 HPI‐associated microbial species (FDR < 0.05, Wilcoxon rank‐sum test): Stenotrophomonas maltophilia, Stenotrophomonas unclassified, Chryseobacterium unclassified, Pedobacter unclassified, Variovorax unclassified, and Pseudomonas stutzeri. Furthermore, 55 gastric microbial pathways were enriched in the H. pylori‐positive group, whereas only 2 pathways were more abundant in the H. pylori‐negative group: dTDP‐L‐rhamnose biosynthesis and tetrapyrrole biosynthesis (FDR < 0.05, Wilcoxon rank‐sum test). Gastritis was not associated with non‐H. pylori species in the stomach (P > 0.05, Wilcoxon rank‐sum test). This study revealed alterations in gastric microbial taxa and function associated with HPI in the Chinese population, which provides an insight into gastric microbial interactions and their potential role in the pathological process of gastric diseases.

Gastric Non-Helicobacter pylori Urease-Positive Staphylococcus epidermidis and Streptococcus salivarius Isolated from Humans Have Contrasting Effects on H. pylori-Associated Gastric Pathology and Host Immune Responses in a Murine Model of Gastric Cancer

In populations with similar prevalence of Helicobacter pylori infection, cancer risk can vary dramatically. Changes in composition or structure of bacterial communities in the stomach, either at the time of exposure or over the course of H. pylori infection, may contribute to gastric pathology. In this study, a population of 37 patients from the low-gastric-cancer-risk (LGCR) region of Tumaco, Colombia, and the high-gastric-cancer-risk (HGCR) region of Túquerres, Colombia, were recruited for gastric endoscopy. Antral biopsy specimens were processed for histology and bacterial isolation. Fifty-nine distinct species among 26 genera were isolated by aerobic, anaerobic, and microaerobic culture and confirmed by 16S rRNA analysis. Urease-positive Staphylococcus epidermidis and Streptococcus salivarius were frequently isolated from gastric biopsy specimens. We asked whether coinfection of H. pylori with urease-positive S. salivarius and/or S. epidermidis had a demonstrable effect on H. pylori-induced gastritis in the germfree (GF) INS-GAS mouse model. Coinfections with S. salivarius and/or S. epidermidis did not affect gastric H. pylori colonization. At 5 months postinfection, GF INS-GAS mice coinfected with H. pylori and S. salivarius had statistically higher pathological scores in the stomachs than mice infected with H. pylori only or H. pylori with S. epidermidis (P < 0.05). S. epidermidis coinfection with H. pylori did not significantly change stomach pathology, but levels of the proinflammatory cytokine genes Il-1β, Il-17A , and Il-22 were significantly lower than in H. pylori-monoinfected mice. This study demonstrates that non-H. pylori urease-positive bacteria may play a role in the severity of H. pylori-induced gastric cancer in humans.

IMPORTANCE Chronic infection with H. pylori is the main cause of gastric cancer, which is a global health problem. In two Colombian populations with high levels of H. pylori prevalence, the regional gastric cancer rates are considerably different. Host genetic background, H. pylori biotype, environmental toxins, and dietary choices are among the known risk factors for stomach cancer. The potential role of non-H. pylori gastric microbiota in gastric carcinogenesis is being increasingly recognized. In this study, we isolated 59 bacterial species from 37 stomach biopsy samples of Colombian patients from both low-gastric-cancer-risk and high-gastric-cancer-risk regions. Urease-positive S. epidermidis and S. salivarius commonly cultured from the stomachs, along with H. pylori, were inoculated into germfree INS-GAS mice. S. salivarius coinfection with H. pylori induced significantly higher gastric pathology than in H. pylori-monoinfected mice, whereas S. epidermidis coinfection caused significantly lower H. pylori-induced proinflammatory cytokine responses than in H. pylori-monoinfected mice. This study reinforces the argument that the non-H. pylori stomach microflora play a role in the severity of H. pylori-induced gastric cancer.

Induction and Regulation of the Innate Immune Response in Helicobacter pylori Infection

Gastric cancer (GC) is the fifth most common cancer and the fourth most common cause of cancer-related death worldwide. The intestinal type of GC progresses from acute to chronic gastritis, multifocal atrophic gastritis, intestinal metaplasia, dysplasia, and carcinoma. Infection of the stomach by Helicobacter pylori, a Gram-negative bacterium that infects approximately 50% of the world's population, is the causal determinant that initiates the gastric inflammation and then disease progression. In this context, the induction of the innate immune response of gastric epithelial cells and myeloid cells by H. pylori effectors plays a critical role in the outcome of the infection. However, only 1% to 3% of infected patients develop gastric adenocarcinoma, emphasizing that other mechanisms regulate the localized non-specific response, including the gastric microbiota and genetic factors. This review summarizes studies describing the factors that induce and regulate the mucosal innate immune response during H. pylori infection.

Probiotics in the treatment of Helicobacter pylori infection: reality and perspective

Helicobacter pylori (H. pylori) infection is one of the most common in the world today, associated with the development of acute or chronic inflammatory diseases of the gastroduodenal tract. In order to eradicate the pathogen, various antibacterial therapy regimens have been proposed, based on the use of several chemotherapeutic drugs and a proton pump inhibitor (PPI). However, recent studies indicate a decrease in antibiotic effectiveness due to both the growth rate of H. pylori resistance and side effects, often due to the development of dysbiosis. One of the promising areas of investigation is the treatment with probiotic therapy of helicobacteriosis. The use of probiotics, in the context of H. pylori infection, has two main reasons. The first is related to the use of certain probiotics to reduce the frequency of undesirable gastrointestinal consequences during H. pylori eradication therapy. The second is associated with the antagonistic effect of individual probiotics on H. pylori and the potentiation of the eradication effect. The purpose of this review was to summarize the latest data on the use of probiotics to enhance H. pylori eradication and to restore the gastrointestinal microbiota. Many unresolved questions, about the choice of the specific composition of the probiotic cocktail, dosage, duration of therapy, mechanisms of the antimicrobial action of probiotics, as well as possible negative consequences of such therapy, remain.

Gut-lung cross talk in COVID-19 pathology and fatality rate

Coronavirus disease 2019 (COVID-19) is the leading pandemic facing the world in 2019/2020; it is caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which necessitates clear understanding of the infectious agent. The virus manifests aggressive behavior with severe clinical presentation and high mortality rate, especially among the elderly and patients living with chronic diseases. In the recent years, the role of gut microbiota, in health and disease, has been progressively studied and highlighted. It is through gut microbiota-organ bidirectional pathways, such as gut-brain axis, gut-liver axis, and gut-lung axis, that the role of gut microbiota in prompting lung disease, among other diseases, has been proposed and accepted. It is also known that respiratory viral infections, such as COVID-19, induce alterations in the gut microbiota, which can influence immunity. Based on the fact that gut microbiota diversity is decreased in old age and in patients with certain chronic diseases, which constitute two of the primary fatality groups in COVID-19 infections, it can be assumed that the gut microbiota may play a role in COVID-19 pathology and fatality rate. Improving gut microbiota diversity through personalized nutrition and supplementation with prebiotics/probiotics will mend the immunity of the body and hence could be one of the prophylactic strategies by which the impact of COVID-19 can be minimized in the elderly and immunocompromised patients. In this chapter, the role of dysbiosis in COVID-19 will be clarified and the possibility of using co-supplementation of personalized prebiotics/probiotics with current therapies will be discussed.

Chronic inflammation and long-lasting changes in the gastric mucosa after Helicobacter pylori infection involved in gastric cancer

OBJECTIVE

Helicobacter pylori (H. pylori) infects approximately half of the world's population, as one of the most common chronic infections. H. pylori infection has been widely recognized as a major risk factor for gastric cancer (GC).

METHODS

Eradication treatment is considered to abolish the inflammatory response and prevent progression to GC. However, only 1-3% of H. pylori-infected patients develop GC, whereas GC can occur even after eradicating H. pylori. In addition, the incidence of GC following H. pylori infection is significantly higher compared to the gross incidence induced by all causes, although eradicating H. pylori reduces the risk of developing GC.

RESULTS

Therefore, it is reasonable to hypothesize that H. pylori infection results in changes that persist even after its eradication. Several of these changes may not be reversible within a short time, including the status of inflammation, the dysfunction of immunity and apoptosis, mitochondrial changes, aging and gastric dysbacteriosis.

CONCLUSION

The present review article aimed to discuss these potential long-lasting changes induced by H. pylori infection that may follow the eradication of H. pylori and contribute to the development of GC.

Gastric Microbiota beyond H. pylori: An Emerging Critical Character in Gastric Carcinogenesis

Gastric cancer (GC) is one of the global leading causes of cancer death. The association between Helicobacter pylori, which is a predominant risk factor for GC, with GC development has been well-studied. Recently, accumulating evidence has demonstrated the presence of a large population of microorganisms other than H. pylori in the human stomach. Existing sequencing studies have revealed microbial compositional and functional alterations in patients with GC and highlighted a progressive shift in the gastric microbiota in gastric carcinogenesis with marked enrichments of oral or intestinal commensals. Moreover, using a combination of gastric bacterial signatures, GC patients could be significantly distinguished from patients with gastritis. These findings, therefore, emphasize the importance of a collective microbial community in gastric carcinogenesis. Here, we provide an overview of non-H. pylori gastric microbes in gastric carcinogenesis. The molecular mechanisms of gastric microbes-related carcinogenesis and potential clinical applications of gastric microbiota as biomarkers of GC are also explored.

A Generalist Lifestyle Allows Rare Gardnerella spp. to Persist at Low Levels in the Vaginal Microbiome

Gardnerella spp. are considered a hallmark of bacterial vaginosis, a dysbiosis of the vaginal microbiome. There are four cpn60 sequence-based subgroups within the genus (A, B, C and D), and thirteen genome species have been defined recently. Gardnerella spp. co-occur in the vaginal microbiome with varying abundance, and these patterns are shaped by a resource-dependent, exploitative competition, which affects the growth rate of subgroups A, B and C negatively. The growth rate of rarely abundant subgroup D, however, increases with the increasing number of competitors, negatively affecting the growth rate of others. We hypothesized that a nutritional generalist lifestyle and minimal niche overlap with the other more abundant Gardnerella spp. facilitate the maintenance of subgroup D in the vaginal microbiome through negative frequency-dependent selection. Using 40 whole-genome sequences from isolates representing all four subgroups, we found that they could be distinguished based on the content of their predicted proteomes. Proteins associated with carbohydrate and amino acid uptake and metabolism were significant contributors to the separation of subgroups. Subgroup D isolates had significantly more of their proteins assigned to amino acid metabolism than the other subgroups. Subgroup D isolates were also significantly different from others in terms of number and type of carbon sources utilized in a phenotypic assay, while the other three could not be distinguished. Overall, the results suggest that a generalist lifestyle and lack of niche overlap with other Gardnerella spp. leads to subgroup D being favoured by negative frequency-dependent selection in the vaginal microbiome.