Participation of microbiota in the development of gastric cancer

Fusobacterium nucleatum: Unraveling its potential role in gastric carcinogenesis

Fusobacterium nucleatum (F. nucleatum) is a Gram-negative anaerobic bacterium that plays a key role in the development of oral inflammation, such as periodontitis and gingivitis. In the last 10 years, F. nucleatum has been identified as a prevalent bacterium associated with colorectal adenocarcinoma and has also been linked to cancer progression, metastasis and poor disease outcome. While the role of F. nucleatum in colon carcinogenesis has been intensively studied, its role in gastric carcinogenesis is still poorly understood. Although Helicobacter pylori infection has historically been recognized as the strongest risk factor for the development of gastric cancer (GC), with recent advances in DNA sequencing technology, other members of the gastric microbial community, and F. nucleatum in particular, have received increasing attention. In this review, we summarize the existing knowledge on the involvement of F. nucleatum in gastric carcinogenesis and address the potential translational and clinical significance of F. nucleatum in GC.

Impact the impact of gut microbiota on gastric cancer via immune cells: a comprehensive Mendelian randomization study and mediation analysis

PURPOSE

Recent observational studies have highlighted the role of altered gut microbiota (GM) in the activation of the host immune system and the resulting of gastric cancer (GC). However, the exact causal relationship and mechanisms of action are still not fully understood.

MATERIALS AND METHODS

Genetic data from published genome-wide association studies (GWASs) were employed to determine the causal effects of 207 taxa and 205 bacterial pathways on GC via two-sample Mendelian randomization (MR) and two-step mediation MR analysis. In this study, 731 immune cell traits served as potential mediators. An inverse variance-weighted (IVW) estimation, augmented by a range of alternative estimators, notably the Bayesian-weighted MR method, was employed as the primary methodological approach.

RESULTS

Four taxa and five bacterial pathways were found to be negatively correlated with GC, whereas one taxon and two bacterial pathways were a positively correlated with GC. Reverse causality was not found in the reverse MR analysis. Additional validation was performed using a sensitivity analysis. Mediation MR analyses revealed that the GM influences GC through various phenotypes of 16 immune cells that act as mediators. For example, s_Alistipes_sp_AP11 was found to inhibit GC through NKT %T cell (total effect: -0.3234, mediation effect: 0.0212). This mediating effect further highlights the complex relationship among GMs, immune cell traits, and their combined effects on GC.

CONCLUSIONS

Our findings highlight the genetic connection between specific GMs and GC, emphasizing the potential role of immune cells as mediators, and offering valuable perspectives on potential therapeutic strategies that manipulating the GM to address GC.

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.

The role of Helicobacter suis, Fusobacterium gastrosuis, and the pars oesophageal microbiota in gastric ulceration in slaughter pigs receiving meal or pelleted feed

This study investigated the role of causative infectious agents in ulceration of the non-glandular part of the porcine stomach (pars oesophagea). In total, 150 stomachs from slaughter pigs were included, 75 from pigs that received a meal feed, 75 from pigs that received an equivalent pelleted feed with a smaller particle size. The pars oesophagea was macroscopically examined after slaughter. (q)PCR assays for H. suis, F. gastrosuis and H. pylori-like organisms were performed, as well as 16S rRNA sequencing for pars oesophagea microbiome analyses. All 150 pig stomachs showed lesions. F. gastrosuis was detected in 115 cases (77%) and H. suis in 117 cases (78%), with 92 cases (61%) of co-infection; H. pylori-like organisms were detected in one case. Higher infectious loads of H. suis increased the odds of severe gastric lesions (OR = 1.14, p = 0.038), while the presence of H. suis infection in the pyloric gland zone increased the probability of pars oesophageal erosions [16.4% (95% CI 0.6-32.2%)]. The causal effect of H. suis was mediated by decreased pars oesophageal microbiome diversity [-1.9% (95% CI - 5.0-1.2%)], increased abundances of Veillonella and Campylobacter spp., and decreased abundances of Lactobacillus, Escherichia-Shigella, and Enterobacteriaceae spp. Higher infectious loads of F. gastrosuis in the pars oesophagea decreased the odds of severe gastric lesions (OR = 0.8, p = 0.0014). Feed pelleting had no significant impact on the prevalence of severe gastric lesions (OR = 1.72, p = 0.28). H. suis infections are a risk factor for ulceration of the porcine pars oesophagea, probably mediated through alterations in pars oesophageal microbiome diversity and composition.

Effect of Lactobacillus plantarum ZFM4 in Helicobacter pylori-infected C57BL/6 mice: prevention is better than cure

Objectives

This study was performed to explore the preventive and therapeutic effects of Lactobacillus plantarum ZFM4 on H. pylori infections of the stomach tissue in C57BL/6 mice.

Methods

In this study, 40 specific-pathogen-free female C57BL/6 mice were randomly divided into five groups, namely, the control, ZFM4 pretreatment) ZFM4 pretreatment before H. pylori infected), model (H. pylori infected), triple therapy (H. pylori infected and treated with triple therapy), and ZFM4 treatment groups (H. pylori infected and treated with ZFM4). The preventive and therapeutic effects of Lactobacillus plantarum ZFM4 were evaluated in H. pylori-infected C57BL/6 mice by assessing gastric tissue morphology, inflammatory cytokine levels, microbial composition, and microbial diversity.

Results

Lactobacillus plantarum ZFM4 was able to survive in low gastric pH and play a role in preventing H. pylori infection. This was evident from a reduction in both, the gastric inflammatory response and expression of inflammatory factors caused by H. pylori infection. Lactobacillus plantarum ZFM4 could also inhibit the growth of H. pylori via its beneficial impact on the gastric microbiota.

Conclusion

Our findings suggest that Lactobacillus plantarum ZFM4 offers superior preventive effects against H. pylori infections when used alone. However, the therapeutic effect on established infections is weaker. Further clinical trials are needed to confirm the specific dosage, duration, and other aspects of administration.

The role of microbiota in the development and treatment of gastric cancer

The stomach was once considered a sterile organ until the discovery of Helicobacter pylori (HP). With the application of high-throughput sequencing technology and macrogenomics, researchers have identified fungi and fivemajor bacterial phyla within the stomachs of healthy individuals. These microbial communities exert regulatory influence over various physiological functions, including energy metabolism and immune responses. HP is a well-recognized risk factor for gastric cancer, significantly altering the stomach's native microecology. Currently, numerous studies are centered on the mechanisms by which HP contributes to gastric cancer development, primarily involving the CagA oncoprotein. However, aside from exogenous infections such as HP and EBV, certain endogenous dysbiosis can also lead to gastric cancer through multiple mechanisms. Additionally, gut microbiota and its metabolites significantly impact the development of gastric cancer. The role of microbial therapies, including diet, phages, probiotics and fecal microbiota transplantation, in treating gastric cancer should not be underestimated. This review aims to study the mechanisms involved in the roles of exogenous pathogen infection and endogenous microbiota dysbiosis in the development of gastric cancer. Also, we describe the application of microbiota therapy in the treatment and prognosis of gastric cancer.

Metagenomic and single-cell RNA-Seq survey of the Helicobacter pylori-infected stomach in asymptomatic individuals

Helicobacter pylori colonization of the gastric niche can persist for years in asymptomatic individuals. To deeply characterize the host-microbiota environment in H. pylori-infected (HPI) stomachs, we collected human gastric tissues and performed metagenomic sequencing, single-cell RNA-Seq (scRNA-Seq), flow cytometry, and fluorescent microscopy. HPI asymptomatic individuals had dramatic changes in the composition of gastric microbiome and immune cells compared with noninfected individuals. Metagenomic analysis uncovered pathway alterations related to metabolism and immune response. scRNA-Seq and flow cytometry data revealed that, in contrast to murine stomachs, ILC2s are virtually absent in the human gastric mucosa, whereas ILC3s are the dominant population. Specifically, proportion of NKp44+ ILC3s out of total ILCs were highly increased in the gastric mucosa of asymptomatic HPI individuals, and correlated with the abundance of selected microbial taxa. In addition, CD11c+ myeloid cells and activated CD4+ T cells and B cells were expanded in HPI individuals. B cells of HPI individuals acquired an activated phenotype and progressed into a highly proliferating germinal-center stage and plasmablast maturation, which correlated with the presence of tertiary lymphoid structures within the gastric lamina propria. Our study provides a comprehensive atlas of the gastric mucosa-associated microbiome and immune cell landscape when comparing asymptomatic HPI and uninfected individuals.

Bacteria and macrophages in the tumor microenvironment

Cancer and microbial infections are significant worldwide health challenges. Numerous studies have demonstrated that bacteria may contribute to the emergence of cancer. In this review, we assemble bacterial species discovered in various cancers to describe their variety and specificity. The relationship between bacteria and macrophages in cancer is also highlighted, and we look for ample proof to establish a biological basis for bacterial-induced macrophage polarization. Finally, we quickly go over the potential roles of metabolites, cytokines, and microRNAs in the regulation of the tumor microenvironment by bacterially activated macrophages. The complexity of bacteria and macrophages in cancer will be revealed as we gain a better understanding of their pathogenic mechanisms, which will lead to new therapeutic approaches for both inflammatory illnesses and cancer.

Gastric bacteria as potential biomarkers for the diagnosis of atrophic gastritis

BACKGROUND

Identification of the risk factors for atrophic gastritis (AG) and prevention of further deterioration of the gastritis are effective approaches to reduce the incidence of gastric cancer. Previous studies found that dysbiosis has been implicated in a wide range of diseases, while the role of gastric bacteria as a biomarker for AG has not been explored.

METHODS AND RESULTS

Gastric juices from cases with non-atrophic gastritis (NAG) and AG were collected for investigation of bacterial composition and function. The β-diversity of microbiota exhibited a significant reduction in AG samples compared with that in NAG samples. Differential abundance analysis revealed that a total of 23 predicted species changed their distributions; meanwhile, all obligate anaerobic bacteria with a relatively high abundance lowered their contents in AG samples. Additionally, the correlation analysis indicated a clear shift in bacterial correlation pattern between the two groups. Functional interrogation of the gastric microbiota showed that bacterial metabolisms associated with enzyme families, digestive system, and endocrine system were downregulated in AG samples. The compositional dissection of "core microbiota" exhibited that oral pathogens, including Porphyromonas gingivalis, Campylobacter gracilis, and Granulicatella elegans, were magnified in AG samples, suggesting that oral diseases may be a trigger factor for early exacerbation of gastritis. Then, the differentially expressed bacteria were used as diagnostic biomarkers for the random forest classifier model for group prediction.

CONCLUSIONS

The results showed that bacterial biomarkers could distinguish AG patients from NAG cases with an accuracy of 90% at the genus level.

Convergent dysbiosis of gastric mucosa and fluid microbiome during stomach carcinogenesis

BACKGROUND

A complex microbiota in the gastric mucosa (GM) has been unveiled recently and its dysbiosis is identified to be associated with gastric cancer (GC). However, the microbial composition in gastric fluid (GF) and its correlation with GM during gastric carcinogenesis are unclear.

METHODS

We obtained GM and GF samples from 180 patients, including 61 superficial gastritis (SG), 55 intestinal metaplasia (IM) and 64 GC and performed 16S rRNA gene sequencing analysis. The concentration of gastric acid and metabolite nitrite has been measured.

RESULTS

Overall, the composition of microbiome in GM was distinct from GF with less diversity, and both were influenced by H. pylori infection. The structure of microbiota changed differentially in GM and GF across histological stages of GC, accompanied with decreased gastric acid and increased carcinogenic nitrite. The classifiers of GC based on microbial markers were identified in both GM and GF, including Lactobacillus, Veillonella, Gemella, and were further validated in an independent cohort with good performance. Interestingly, paired comparison between GM and GF showed that their compositional distinction remarkably dwindled from SG to GC, with some GF-enriched bacteria significantly increased in GM. Moreover, stronger interaction network between microbes of GM and GF was observed in GC compared to SG.

CONCLUSION

Our results, for the first time, revealed a comprehensive profile of both GM and GF microbiomes during the development of GC. The convergent microbial characteristics between GM and GF in GC suggest that the colonization of carcinogenic microbes in GM might derive from GF.

The Challenges of Eradicating Pediatric Helicobacter pylori Infection in the Era of Probiotics

Helicobacter pylori (H. pylori), the most common infection of childhood, results in life-threatening complications during adulthood if left untreated. Most of these complications are related to H. pylori-induced chronic inflammation. The dysbiosis caused by H. pylori is not limited to the gastric microenvironment, but it affects the entire gastrointestinal tract. Eradication of H. pylori has recently become a real challenge for clinicians due to both the persistent increase in antibiotic resistance worldwide and the wide spectrum of side effects associated with the eradication regimens resulting; therefore, there is an urgent need for more effective and less noxious treatment options. Thus, probiotics might be a promising choice in both adults and children with H. pylori infection since their role in improving the eradication rate of this infection has been proved in multiple studies. The positive effects of probiotics might be explained by their abilities to produce antimicrobial compounds and antioxidants, alter local gastric pH, and subsequently decrease H. pylori colonization and adherence to gastric epithelial cells. Nevertheless, if used alone probiotics do not considerably increase the eradication rate.

The impact of Helicobacter pylori infection, eradication therapy, and probiotics intervention on gastric microbiota in young adults

BACKGROUND

The impact of probiotics on non-Helicobacter pylori gastric microbiota and its role in microbial restoration after eradication were relatively unknown. We aimed to explore the effect of H. pylori eradication and probiotic intervention on gastric microbiota in young adults.

METHODS

Fifty-six H. pylori-negative and 95 H. pylori-positive subjects aged 19-30 were included in this study. H. pylori-infected individuals were randomly assigned to quadruple therapy, probiotics supplemented quadruple therapy, or probiotics monotherapy group. Gastric mucosa and gastric juice samples were collected before and 2 months after treatment for 16SrRNA gene sequencing.

RESULTS

The gastric microbial community structure and composition differed from H. pylori-negative subjects 2 months after successful H. pylori eradication. The α diversity of gastric mucosal microbiota significantly increased and was higher than H. pylori-negative subjects, while the α diversity of gastric juice microbiota decreased and was lower than the H. pylori-negative. After probiotics supplemented eradication treatment, Bifidobacterium was enriched in gastric mucosa, Lactobacillus was enriched in gastric juice, potentially pathogenic bacteria such as Fusobacterium and Campylobacter decreased, and the microbial diversity was closer to that of H. pylori-negative subjects compared to quadruple therapy group. Probiotics monotherapy significantly altered the diversity, community structure, and composition of gastric microbiota but showed no advantage in H. pylori inhibition and upregulating beneficial bacteria such as Bifidobacterium and Lactobacillus and related metabolism pathways. Certain potentially pathogenic bacteria such as Fusobacterium increased after probiotic monotherapy.

CONCLUSION

H. pylori eradication significantly disrupted gastric microbiota in young adults and could not be restored in a short time. Probiotics supplementation partially helped restore the gastric dysbiosis caused by eradication therapy, but it might be unnecessary for H. pylori-infected young adults to take probiotics alone.

Overgrowth of Lactobacillus in gastric cancer

Dysbiosis of the gastric microbiome is involved in the development of gastric cancer (GC). A number of studies have demonstrated an increase in the relative abundance of Lactobacillus in GC. In this review, we present data that support the overgrowth of Lactobacillus in GC from studies on molecular and bacterial culture of the gastric microbiome, discuss the heterogenic effects of Lactobacillus on the health of human stomach, and explore the potential roles of the overgrowth of Lactobacillus in gastric carcinogenesis. Further studies are required to examine the association between Lactobacillus and GC at strain and species levels, which would facilitate to elucidate its role in the carcinogenic process.

Gastric Microenvironment-A Partnership between Innate Immunity and Gastric Microbiota Tricks Helicobacter pylori

Helicobacter pylori (H. pylori) carcinogenicity depends on three major factors: bacterial virulence constituents, environmental factors and host's genetic susceptibility. The relationship between microenvironmental factors and H. pylori virulence factors are incontestable. H. pylori infection has a major impact on both gastric and colonic microbiota. The presence of non-H. pylori bacteria within the gastric ecosystem is particularly important since they might persistently act as an antigenic stimulus or establish a partnership with H. pylori in order to augment the subsequent inflammatory responses. The gastric ecosystem, i.e., microbiota composition in children with H. pylori infection is dominated by Streptoccocus, Neisseria, Rothia and Staphylococcus. The impairment of this ecosystem enhances growth and invasion of different pathogenic bacteria, further impairing the balance between the immune system and mucosal barrier. Moreover, altered microbiota due to H. pylori infection is involved in increasing the gastric T regulatory cells response in children. Since gastric homeostasis is defined by the partnership between commensal bacteria and host's immune system, this review is focused on how pathogen recognition through toll-like receptors (TLRs-an essential class of pathogen recognition receptors-PRRs) on the surface of macrophages and dendritic cells impact the immune response in the setting of H. pylori infection. Further studies are required for delineate precise role of bacterial community features and of immune system components.

Impact of Environmental and Pharmacologic Changes on the Upper Gastrointestinal Microbiome

Diseases of the upper gastrointestinal tract have become more prevalent over time. Mechanisms of disease formation are still only partially understood. Recent literature has shown that the surrounding microbiome affects the propensity for disease formation in various parts of the upper gastrointestinal tract. A review was performed of any literature to our best knowledge concerning the effects of pharmacologic agents, environmental changes, and surgical intervention on the microbiome of the upper gastrointestinal tract. Searches of the literature were performed using specific keywords related to drugs, surgical procedures, and environmental factors. Many prescription and nonprescription drugs that are commonly used have varying effects on the upper gastrointestinal tract. Proton pump inhibitors may affect the relative prevalence of some organisms in the lower esophagus and have less effect in the proximal esophagus. Changes in the esophageal microbiome correlate with some esophageal diseases. Drugs that induce weight loss have also been shown to affect the microbiomes of the esophagus and stomach. Common surgical procedures are associated with shifts in the microbial community in the gastrointestinal tract. Environmental factors have been shown to affect the microbiome in the upper gastrointestinal tract, as geographic differences correlate with alterations in the microbiome of the gastrointestinal tract. Understanding the association of environmental and pharmacologic changes on the microbiome of the upper gastrointestinal tract will facilitate treatment plans to reduce morbidity from disease.

Gut microbiome analysis as a predictive marker for the gastric cancer patients

Gut microbiota have been implicated in the development of cancer. Colorectal and gastric cancers, the major gastrointestinal tract cancers, are closely connected with the gut microbiome. Nevertheless, the characteristics of gut microbiota composition that correlate with gastric cancer are unclear. In this study, we investigated gut microbiota alterations during the progression of gastric cancer to identify the most relevant taxa associated with gastric cancer and evaluated the potential of the microbiome as an indicator for the diagnosis of gastric cancer. Compared with the healthy group, gut microbiota composition and diversity shifted in patients with gastric cancer. Different bacteria were used to design a random forest model, which provided an area under the curve value of 0.91. Verification samples achieved a true positive rate of 0.83 in gastric cancer. Principal component analysis showed that gastritis shares some microbiome characteristics of gastric cancer. Chemotherapy reduced the elevated bacteria levels in gastric cancer by more than half. More importantly, we found that the genera Lactobacillus and Megasphaera were associated with gastric cancer.Key Points• Gut microbiota has high sensitivity and specificity in distinguishing patients with gastric cancer from healthy individuals, indicating that gut microbiota is a potential noninvasive tool for the diagnosis of gastric cancer.• Gastritis shares some microbiota features with gastric cancer, and chemotherapy reduces the microbial abundance and diversity in gastric cancer patients.• Two bacterial taxa, namely, Lactobacillus and Megasphaera, are predictive markers for gastric cancer.

Gastric cancer: a comprehensive review of current and future treatment strategies

Gastric cancer remains a major unmet clinical problem with over 1 million new cases worldwide. It is the fourth most commonly occurring cancer in men and the seventh most commonly occurring cancer in women. A major fraction of gastric cancer has been linked to variety of pathogenic infections including but not limited to Helicobacter pylori (H. pylori) or Epstein Barr virus (EBV). Strategies are being pursued to prevent gastric cancer development such as H. pylori eradication, which has helped to prevent significant proportion of gastric cancer. Today, treatments have helped to manage this disease and the 5-year survival for stage IA and IB tumors treated with surgery are between 60 and 80%. However, patients with stage III tumors undergoing surgery have a dismal 5-year survival rate between 18 and 50% depending on the dataset. These figures indicate the need for more effective molecularly driven treatment strategies. This review discusses the molecular profile of gastric tumors, the success, and challenges with available therapeutic targets along with newer biomarkers and emerging targets.

Autoimmune Gastritis and Gastric Microbiota

Autoimmune atrophic gastritis is an organ-specific immune-mediated condition characterized by atrophy of the oxyntic mucosa. Autoimmune atrophic gastritis (AIG) is characterized by a progressive loss of acid-secreting parietal cells leading to hypo-achlorhydria. Due to this peculiar intra-gastric environment, gastric microbiota composition in individuals with autoimmune atrophic gastritis was first supposed and then recently reported to be different from subjects with a normal acidic healthy stomach. Recent data confirm the prominent role of Helicobacter pylori as the main bacterium responsible for gastric disease and long-term complications. However, other bacteria than Helicobacter pylori, for example, Streptococci, were found in subjects who developed gastric cancer and in subjects at risk of this fearful complication, as well as those with autoimmune gastritis. Gastric microbiota composition is challenging to study due to the acidic gastric environment, the difficulty of obtaining representative samples of the entire gastric microbiota, and the possible contamination by oral or throat microorganisms, which can potentially lead to the distortion of the original gastric microbial composition, but innovative molecular approaches based on the analysis of the hyper-variable region of the 16S rRNA gene have been developed, permitting us to obtain an overall microbial composition view of the RNA gene that is present only in prokaryotic cells.

The diffuse-type gastric cancer epidemiology enigma

Background

Intestinal and diffuse gastric adenocarcinomas differ in clinical, epidemiological and molecular features. However, most of the concepts related to the intestinal-type are translated to gastric adenocarcinoma in general; thus, the peculiarities of the diffuse-type are underappreciated.

Results

Besides its growing importance, there are many gaps about the diffuse-type carcinogenesis and, as a result, its epidemiologic and pathogenetic features remain poorly understood.

Conclusions

Alternative hypotheses to explain these features are discussed, including the role of the gastric microbiota, medical therapies, and modifications in the stomach’s microenvironment.

Gastric Mucosa-Associated Microbial Signatures of Early Gastric Cancer

Alterations in the microbiome are associated with the development of gastric cancer. Our study aimed to identify dysbiotic features in early gastric cancer (EC). The gastric microbiome was assessed in EC (n = 30), advanced gastric cancer (AC) (n = 30), and chronic gastritis (CG) (n = 60). The results demonstrated significant differences in the microbial profile and composition between EC and AC, suggesting alterations associated with gastric cancer progression. Linear discriminant analysis (LDA) effect size (LEfSe) analyses identified 32 bacterial genera that were associated with EC. Functional analyses of the gastric microbiome showed that the production of urease and synthesis of bacterial flagella were weakened in EC, while the glycolysis of fructose and hydrolysis of glycosides were enhanced. A classifier based on a random forest (RF) machine learning algorithm identified a microbial signature that distinguished EC from CG or AC with high accuracy. The correct identification of the signature was further validated in independent cohorts. This signature enriched of bacteria with varied abundance, high degree of bacterial interactions and carcinogenic potentials. Constrained principal coordinate analyses revealed that the presence of Helicobacter pylori and the cagA and vacA virulence genotypes influenced the structure of the gastric microbiome. To determine the impacts of host genetic variations on the gastric microbiome, six previously reported single nucleotide polymorphisms (SNPs) were examined. The minor allele of MUC1 rs4072037 was associated with an increased abundance of Ochrobactrum. The gastric microbiome altered in EC, which might be attributed in part to host genetic variations, H. pylori infection, bacterial virulence and environmental adaptations. The identified microbial signature could serve as biomarkers for clinical assessment of gastric cancer risk in high-risk patients.

Dysbiosis of gut microbiota is associated with gastric carcinogenesis in rats

OBJECTIVES

Although many studies have examined changes in gut microbiota composition in gastric carcinogenesis to clarify the mechanism of action of anticancer drugs, it is unclear whether animal models of gastric carcinogenesis adequately reflect the disease in humans.

METHODS

To address this issue, the present study investigated changes in the gut microbiome profile of a rat model of gastric carcinogenesis established using a combination of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), sodium salicylate, irregular fasting, and ranitidine. The rats were divided into control (Normal), chronic non-atrophic gastritis (CNAG), chronic atrophic gastritis (CAG), precancerous lesion of gastric cancer (PLGC), and gastric cancer (GC) groups according to histopathological features. Gut microbiome in gastric carcinogenesis profiling was performed by 16S rRNA gene sequencing of rat feces samples.

RESULTS

We found that gut bacterial species richness increased whereas species diversity decreased during gastric carcinogenesis, with the most significant changes detected in the PLGC group. Gut microbiota community composition differed across groups, with the greatest similarities observed between CNAG and CAG groups and between PLGC and GC groups. There were significant differences in taxonomic representation at the phylum level: the PLGC group had the highest ratio of Firmicutes/Bacteroidetes whereas the GC group had the highest abundance of Proteobacteria and Actinobacteria.

CONCLUSIONS

These results indicate that changes in the gut microbiome in a rat model of MNNG-induced gastric carcinogenesis are similar to those observed in humans, thus providing a useful tool for evaluating the efficacy and mechanism of action of novel monotherapies or drug combinations for the treatment of gastric carcinogenesis.

Systematic review: gastric microbiota in health and disease

BACKGROUND

Helicobacter pylori is the most infamous constituent of the gastric microbiota and its presence is the strongest risk factor for gastric cancer and other gastroduodenal diseases. Although historically the healthy stomach was considered a sterile organ, we now know it is colonised with a complex microbiota. However, its role in health and disease is not well understood.

AIM

To systematically explore the literature on the gastric microbiota in health and disease as well as the gut microbiota after bariatric surgery.

METHODS

A systematic search of online bibliographic databases MEDLINE/EMBASE was performed between 1966 and February 2019 with screening in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomised controlled trials, cohort studies and observational studies were included if they reported next-generation sequencing derived microbiota analysis on gastric aspirate/tissue or stool samples (bariatric surgical outcomes).

RESULTS

Sixty-five papers were eligible for inclusion. With the exception of H pylori-induced conditions, overarching gastric microbiota signatures of health or disease could not be determined. Gastric carcinogenesis induces a progressively altered microbiota with an enrichment of oral and intestinal taxa as well as significant changes in host gastric mucin expression. Proton pump inhibitors usage increases gastric microbiota richness. Bariatric surgery is associated with an increase in potentially pathogenic proteobacterial species in patient stool samples.

CONCLUSION

While H pylori remains the single most important risk factor for gastric disease, its capacity to shape the collective gastric microbiota remains to be fully elucidated. Further studies are needed to explore the intricate host/microbial and microbial/microbial interplay.

High-Salt Diet-Induced Gastritis in C57BL/6 Mice is Associated with Microbial Dysbiosis and Alleviated by a Buckwheat Diet

SCOPE

A high-salt diet is a cause of gastritis, but the associated mechanism remains unclear. Recent studies have shown that gastric flora is associated with a variety of stomach diseases, but it is not known whether gastric flora is involved in gastritis induced by a high-salt diet.

METHODS AND RESULTS

Gastritis is successfully induced in C57BL/6 mice fed a high-salt diet (salt: 5% NaCl) for four weeks. Through 16S rRNA gene sequencing, the composition of the stomach microbiota of mice fed normal and high-salt diets are compared, the results of which show that the high-salt diet induces significant changes in the gastric flora. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) is used to predict the function of the microbiota in the stomach of mice, and the results indicate that a high-salt diet leads to a decrease in the ability of the gastric microbiota to metabolize polysaccharides and vitamins. A buckwheat diet is used to treat gastritis. The results show gastritis induced by the high-salt diet is significantly alleviated, and the dysbiosis in the stomach also improved.

CONCLUSION

Buckwheat diet may be one of the ways to prevent and treat gastritis caused by a high-salt diet.

Role and significance of traditional Chinese medicine in regulating gastrointestinal microecology to prevent and treat gastrointestinal cancer

Recent studies have shown that gastrointestinal microecology is closely related to the occurrence and development of gastrointestinal cancers and anti-tumor treatment efficacy, so effective regulation of gastrointestinal microecology plays an important role in the prevention and treatment of gastrointestinal cancers. Traditional Chinese medicine, adopting oral administration, can directly regulate gastrointestinal microecology. Traditional Chinese medicine can improve the precancerous condition and enhance the clinical efficacy of anti-tumor treatment via multiple mechanisms, such as improving the microecological structure of the gastrointestinal tract, protecting the gastrointestinal mucosal barrier, preventing the translocation of the flora, and enhancing the immune function of the gastrointestinal mucosa. Some research has shown that the imbalance of gastrointestinal microecology is closely related to spleen deficiency syndrome and damp-heat syndrome. The therapeutic principles of traditional Chinese medicine can be Jianpi Hewei and Qingre Qushi following the concept of "combination of disease and syndrome". It is of great significance to prevent and cure gastrointestinal tumors from a new perspective of regulating intestinal microecology. We hope of providing new strategies for the anti-tumor research of traditional Chinese medicine.

Microflora composition in the gastrointestinal tract in patients with Barrett's esophagus

Background

The incidence of esophageal adenocarcinoma (EAC) has been increasing over the last 40 years. While Barrett's esophagus is a known risk factor for the development of EAC, the role of the microflora in the development of EAC is still largely unknown and is being investigated further by multiple centers. Our goal was to identify trends in microflora composition along various aspects of the upper gastrointestinal tract in patients with Barrett's esophagus.

Methods

After obtaining institutional review board approval, 12 patients agreed to participate in the study. While endoscopy was performed for surveillance Barrett's monitoring, additional biopsies of esophageal mucosa were taken from the (I) proximal esophagus, (II) mid-esophagus, (III) distal esophagus, and (IV) Barrett's esophagus. Additional swabs were also taken from the uvula and the endoscope used during the procedure. The swabs from the uvula and endoscope were obtained prior to the endoscope entering the stomach, to prevent exposing the endoscope to the acidic environment of the stomach. The most common bacterial elements were identified by amplifying sample DNA using a panel of 5 "universal" fusion primer pairs. The 400-500 base pair fragments created an overlap which covered 95% of the bacterial 16s gene.

Results

Throughout the esophagus, 34 bacterial genera were found which had a relative abundance of >1.0. Streptococcal genera were prevalent in all aspects of the esophagus, ranging from 16% to 70% of the bacterial community. Haemophilus genera were uniquely abundant in the Barrett's esophageal tissue but relatively absent elsewhere in the upper gastrointestinal tract. Overall, the percentage of Gram-positive organisms was much higher in the proximal than distal esophagus. The microflora pattern obtained from the uvula and endoscopic swabs did not correlate with any of the tissue biopsies along any aspect of the esophagus.

Conclusions

In patients with Barrett's esophagus, Streptococcal genera are widespread throughout the esophagus. Gram-positive genera tend to decrease as a percentage of overall flora distally. Obtaining a simple swab of the oropharynx or endoscope itself appears to be a poor substitute for tissue biopsy of esophageal mucosa when evaluating microflora patterns.

Microbiota according to gastric topography in patients with low or high risk of gastric cancer in Nariño, Colombia

Introduction: Inflammation in the gastric antrum caused by Helicobacter pylori increases the risk of duodenal ulcer while inflammation in the body generates atrophic gastritis and increased risk of gastric cancer. These inflammatory responses according to gastric topography could be explained by the composition of the gastric microbiota associated with H. pylori. Objective: To identify and compare the microbiota of the gastric antrum and body of individuals from two populations, one with high risk and one with low risk of gastric cancer from Nariño, Colombia. Materials and methods: Biopsies of the gastric antrum and body of patients with non-atrophic gastritis or metaplastic atrophic gastritis were included. The microbiota was defined by sequencing the 16S rRNA gene, V3-V4 region, (illumina-MiSeq™). The operational taxonomic units were classified using the BLASTn and RDPII databases. The differences among microbial populations were evaluated with the PERMANOVA and multivariate analyses. Results: The Epsilonproteobacteria class represented by H. pylori was more abundant in the antrum and body biopsies of individuals with metaplastic atrophic gastritis (>50%) while in individuals with non-atrophic gastritis it was 20 % and had greater metagenomic diversity. Helicobacter pylori infection significantly decreases the metagenomic diversity of the gastric antrum (p=0.005) compared to that of the body. Conclusions: The bacterial groups involved in the dysbiosis can colonize both topographic regions of the stomach, regardless of the sectorized inflammation responses. Helicobacter pylori infection associated with the gastric microbiota is related to its localization in the stomach, the type of lesion, and the population at risk of gastric cancer, which suggests its importance in microbial dysbiosis and gastric disease.

Detection of Microbial 16S rRNA Gene in the Serum of Patients With Gastric Cancer

Aberrance in the blood bacterial microbiome has been identified and validated in several non-infectious diseases, including cancer. The occurrence and progression of gastric cancer has been found to be associated with alterations in the microbiome composition. However, the composition of the blood microbiome in patients with gastric cancer is not well-characterized. To test this hypothesis, we conducted a case-control study to investigate the microbiota compositions in the serum of patients with gastric cancer. The serum microbiome was investigated in patients with gastric cancer, atypical hyperplasia, chronic gastritis, and in healthy controls using 16S rRNA gene sequencing targeting the V1-V2 region. Our results revealed that the structure of the serum microbiome in gastric cancer was significantly different from all other groups, and alpha diversity decreased from the healthy control to patients with gastric cancer. The serum microbiome correlated significantly with tumor-node-metastasis (TNM) stage, lymphatic metastasis, tumor diameter, and invasion depth in gastric cancer. Three genera or species, namely, Acinetobacter, Bacteroides, Haemophilus parainfluenzae, were enriched in patients with gastric cancer, whereas Sphingomonas, Comamonas, and Pseudomonas stutzeri were enriched in the healthy control. Furthermore, the structure of serum microbiota differed between gastric cancer lymphatic metastasis and non-lymphatic metastasis. As a pilot investigation to characterizing the serum microbiome in gastric cancer, our study provided a foundation for improving our understanding of the role of microbiota in the pathogenesis of gastric cancer.

Modification of the Gastric Mucosal Microbiota by a Strain-Specific Helicobacter pylori Oncoprotein and Carcinogenic Histologic Phenotype

Microbial communities are essential for the maintenance of human health, and when these communities are altered, hosts can become susceptible to inflammation and disease. Dysbiosis contributes to gastrointestinal cancers, and specific bacterial species are associated with this phenotype. This study uses a robust and reproducible animal model to demonstrate that H. pylori infection induces gastric dysbiosis in a cagA-dependent manner and further that dysbiosis and altered microbial community structure parallel the severity of H. pylori-induced gastric injury. Ultimately, such models of H. pylori infection and cancer that can effectively evaluate multiple determinants simultaneously may yield effective strategies for manipulating the gastric microbiota to prevent the development of gastric cancer.

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma; however, most infected individuals never develop this malignancy. Strain-specific microbial factors, such as the oncoprotein CagA, as well as environmental conditions, such as iron deficiency, augment cancer risk. Importantly, dysbiosis of the gastric microbiota is also associated with gastric cancer. To investigate the combinatorial effects of these determinants in an in vivo model of gastric cancer, Mongolian gerbils were infected with the carcinogenic cag⁺H. pylori strain 7.13 or a 7.13 cagA isogenic mutant, and microbial DNA extracted from gastric tissue was analyzed by 16S rRNA sequencing. Infection with H. pylori significantly increased gastric inflammation and injury, decreased α-diversity, and altered microbial community structure in a cagA-dependent manner. The effect of iron deficiency on gastric microbial communities was also investigated within the context of infection. H. pylori-induced injury was augmented under conditions of iron deficiency, but despite differences in gastric pathology, there were no significant differences in α- or β-diversity, phyla, or operational taxonomic unit (OTU) abundance among infected gerbils maintained on iron-replete or iron-depleted diets. However, when microbial composition was stratified based solely on the severity of histologic injury, significant differences in α- and β-diversity were present among gerbils harboring premalignant or malignant lesions compared to gerbils with gastritis alone. This study demonstrates that H. pylori decreases gastric microbial diversity and community structure in a cagA-dependent manner and that as carcinogenesis progresses, there are corresponding alterations in community structure that parallel the severity of disease.

Microbial biomarkers of common tongue coatings in patients with gastric cancer

PURPOSE

The study aims to explore the characteristic microorganisms of the common tongue coatings in patients with gastric cancer (GC).

METHODS

A total of 115 GC patients were assigned to four groups: White-thin coating (W-thin) group, White-thick coating (W-thick) group, Yellow-thin coating (Y-thin) group and Yellow-thick coating (Y-thick) group. Thirty-five healthy volunteers with White-thin coating were recruit as controls. High-throughput sequencing was used to describe the microbial community of the tongue coatings based on 16S rRNA and 18S rRNA genes. Multi-factors statistical analysis was carried out to present the microbial biomarkers of the tongue coating in GC patients.

RESULTS

At bacterial phylum level, Saccharibacteria had higher relative abundance in W-thick group than W-thin group, Proteobacteria was more abundant in W-thin group than Y-thick group and less abundant in Y-thick group than Y-thin group. At fungal genus level, Guehomyces and Aspergillus presented to be significantly different among the common tongue coatings. Forteen significantly increased taxa were sorted out as the microbial biomarkers of common tongue coatings by LEfSe and ROC analysis. At species level, bacterial Capnocytophaga leadbetteri and fungal Ampelomyces_sp_IRAN_1 may be the potential biomarkers of W-thin coating, four bacterial species (Megasphaera micronuciformis, Selenomonas sputigena ATCC 35185, Acinetobacter ursingii, Prevotella maculosa) may be the potential biomarkers of W-thick coating. In general, the white coatings held more complex commensal relationship than the yellow coatings.

CONCLUSION

The common tongue coating owned characteristic microorganisms and special commensal relationship in the GC patients.

Relationship of the mucosal microbiota to gastrointestinal inflammation and small cell intestinal lymphoma in cats

Background

The gastrointestinal (GI) microbiota in healthy cats is altered in IBD. Little research has been performed to identify whether specific bacterial groups are associated with small cell GI lymphoma (LSA).

Hypothesis

Mucosal bacteria, including Enterobacteriaceae and Fusobacterium spp., are abundant in intestinal biopsies of cats with small cell GI LSA compared to cats with IBD.

Animals

Fourteen cats with IBD and 14 cats with small cell GI LSA.

Methods

Retrospective case control study. A search of the medical records was performed to identify cats diagnosed with IBD and with GI LSA. Bacterial groups identified by FISH in GI biopsies were compared between cohorts and correlated to CD11b⁺ and NF‐κB expression.

Results

Fusobacterium spp. (median; IQR bacteria/region) were higher in cats with small cell GI LSA in ileal (527; 455.5 – 661.5; P = .046) and colonic (404.5; 328.8 – 455.5; P = .016) adherent mucus, and combined colonic compartments (free mucus, adherent mucus, attaching to epithelium) (8; 0 – 336; P = .017) compared to cats with IBD (ileum: 67; 31.5 – 259; colon: 142.5; 82.3 – 434.5; combined: 3; 0 – 34). Bacteroides spp. were higher in ileal adherent mucus (P = .036) and 3 combined ileal compartments (P = .034) of cats with small cell GI LSA. There were significant correlations between Fusobacterium spp. totals and CD11b⁺ cell (P = .009; rs .476) and NF‐κB expression (P = .004; rs .523).

Conclusions

The bacterial alterations appreciated might be influential in development of small cell GI LSA, and should drive further studies to elucidate the effects of microbial‐mediated inflammation on GI cancer progression.

IVTH BRAZILIAN CONSENSUS CONFERENCE ON HELICOBACTER PYLORI INFECTION

ABSTRACT Significant progress has been obtained since the III Brazilian Consensus Conference on H. pylori infection held in 2012, in Bento Gonçalves, Brazil, and justify a fourth meeting to establish updated guidelines on the current management of H. pylori infection. Therefore, the Núcleo Brasileiro para Estudo do Helicobacter pylori e Microbiota (NBEHPM), association linked to Brazilian Federation of Gastroenterology (FBG) held its fourth meeting again in Bento Gonçalves, RS, Brazil, on August 25-27, 2017. Twenty-six delegates, including gastroenterologists, endoscopists, and pathologists from the five regions of Brazil as well as one international guest from the United States, participated in the meeting. The participants were invited based on their knowledge and contribution to the study of H. pylori infection. The meeting sought to review different aspects of treatment for infection; establish a correlation between infection, dyspepsia, intestinal microbiota changes, and other disorders with a special emphasis on gastric cancer; and reassess the epidemiological and diagnostic aspects of H. pylori infection. Participants were allocated into four groups as follows: 1) Epidemiology and Diagnosis, 2) Dyspepsia, intestinal microbiota and other afections, 3) Gastric Cancer, and, 4) Treatment. Before the consensus meeting, participants received a topic to be discussed and prepared a document containing a recent literature review and statements that should be discussed and eventually modified during the face-to-face meeting. All statements were evaluated in two rounds of voting. Initially, each participant discussed the document and statements with his group for possible modifications and voting. Subsequently, during a second voting in a plenary session in the presence of all participants, the statements were voted upon and eventually modified. The participants could vote using five alternatives: 1) strongly agree; 2) partially agree; 3) undecided; 4) disagree; and 5) strongly disagree. The adopted consensus index was that 80% of the participants responded that they strongly or partially agreed with each statement. The recommendations reported are intended to provide the most current and relevant evidences to management of H. pylori infection in adult population in Brazil.

Common Variable Immunodeficiency and Gastric Malignancies

Common variable immunodeficiency (CVID) is an immunodeficiency disorder with a high incidence of gastrointestinal manifestations and an increased risk of gastric carcinoma and lymphoma. This review discusses the latest advancements into the immunological, clinical and diagnostic aspects of gastric malignancies in patients with CVID. The exact molecular pathways underlying the relationships between CVID and gastric malignancies remain poorly understood. These include genetics, immune dysregulation and chronic infections by Helicobacter pylori. Further studies are needed to better stratify the risk for cancer in these patients, to elaborate surveillance programs aimed at preventing these complications, and to develop new and more effective therapeutic approaches.

Gastric microbiota and carcinogenesis: the role of non-Helicobacter pylori bacteria - A systematic review

BACKGROUND AND AIM

Helicobacter pylori is the strongest risk factor for gastric cancer. However, recent advances in DNA sequencing technology have revealed a complex microbial community in the stomach that could also contribute to the development of gastric cancer. The aim of this study was to present recent scientific evidence regarding the role of non-Helicobacter pylori bacteria in gastric carcinogenesis.

METHODS

A systematic review of original articles published in PubMed in the last ten years related to gastric microbiota and gastric cancer in humans was performed.

RESULTS

Thirteen original articles were included. The constitution of gastric microbiota appears to be significantly affected by gastric cancer and premalignant lesions. In fact, differences in gastric microbiota have been documented, depending on Helicobacter pylori status and gastric conditions, such as non-atrophic gastritis, intestinal metaplasia and cancer. Gastric carcinogenesis can be associated with an increase in many bacteria (such as Lactobacillus coleohominis, Klebsiella pneumoniae or Acinetobacter baumannii) as well as decrease in others (such as Porphyromonas spp, Neisseria spp, Prevotella pallens or Streptococcus sinensis). However, there is no conclusive data that confirms if these changes in microbiota are a cause or consequence of the process of carcinogenesis.

CONCLUSIONS

Even though there is limited evidence in humans, microbiota differences between normal individuals, pre-malignant lesions and gastric cancer could suggest a progressive shift in the constitution of gastric microbiota in carcinogenesis, possibly resulting from a complex cross-talk between gastric microbiota and Helicobacter pylori. However, further studies are needed to elucidate the specific role (if any) of different microorganisms.

The interaction between smoking, alcohol and the gut microbiome

The gastrointestinal microbiome is a complex echosystem that establishes a symbiotic, mutually beneficial relation with the host, being rather stable in health, but affected by age, drugs, diet, alcohol, and smoking. Alcohol and smoking contribute to changes in the stomach and affect H pylori-related disorders including the risk of gastric cancer. In the small intestine and in the colon alcohol causes depletion of bacteria with anti-inflammatory activity, eventually resulting in intestinal damage with "leaky gut". These changes contribute to hepatic damage in both alcoholic and non-alcoholic liver disease and have been associated with other disorders. Lactobacillus GG and A. muciniphila exert a protective effect in this setting. Smoking leads to modifications of the gut microbiome linked with a protective effect toward ulcerative colitis and deleterious for Crohn's disease. The exact cause-effect relation between alcohol and smoking and changes of the gastrointestinal microbiome needs further exploration with high throughput methodologies, and controlled studies are necessary to define the role of microbiome modulation on the immune response and systemic activation of pro-inflammatory pathways.

Hunger and microbiology: is a low gastric acid-induced bacterial overgrowth in the small intestine a contributor to malnutrition in developing countries?

Underproduction of hydrochloric acid into the stomach is frequently encountered in subjects from developing countries. We explore the hypothesis that hypochlorhydria compromises the gastric barrier and favours bacterial overgrowth in the proximal parts of the small intestine where nutrient absorption takes place. Food calories are thus deviated into bacterial metabolism. In addition to an adequate caloric supply, correcting hypochlorhydria might be needed to decrease childhood malnutrition.

Alteration of stomach microbiota compositions in the progression of gastritis induces nitric oxide in gastric cell

Atrophic gastritis is considered to be an antecedent to intestinal metaplasia and gastric cancer. A previous study identified that Helicobacter pylori was absent at the severe atrophic gastritis stage, and alterations in the gastric microbial composition resembled those in gastric cancer. To explore the role of the bacteria absence of H. pylori in gastric carcinogenesis, in the current study, we compared the microbiota of clinically collected H. pylori-free gastric fluids from 30 patients with non-atrophic gastritis (N) and 22 patients with severe atrophic gastritis (S). We estimated the bacterial loads in the N and S groups by colony counting in culture agar as well as by measuring the concentration of the extracted DNA. The results showed a significant increase in bacterial load in patients with atrophic gastritis in comparison to non-atrophic gastritis. Then, we analyzed the microbial communities of the gastric fluids from all 52 patients using high-throughput sequencing of 16S rRNA amplicons. The Chao 1, Shannon and Simpson diversity indexes demonstrated that the bacterial richness and diversity were not significantly different between the N and S groups. Moreover, principal component analysis illustrated that the microbiomes from the S group were more scattered. Microbiota composition analysis showed that the entire dataset was clustered into 27 phyla, 61 classes, 106 orders, 177 families, 292 genera and 121 species. At the genus level, only the abundance of Prevotella was significantly different between the N and S groups. Further analysis showed that all the higher taxonomic categories were significantly different between the N and S groups. To assess the effects of the metabolic products of Prevotella spp. on gastric cell physiology, we treated the human gastric epithelial cell line AGS with acetic acid and monitored nitric oxide (NO) production. The results showed that acetic acid at low concentrations (0.5 and 5 µM) significantly inhibited AGS cells to secrete NO compared to phosphate buffer saline-treated control cells. These results suggest that the microbiota in non-atrophic gastritis may influence gastric epithelial cell physiology.

Bacterial Diversity of the Gastric Content of Preterm Infants during Their First Month of Life at the Hospital

Studies focused on the stomach microbiota are relatively scarce, and most of them are focused on the adult population. The aim of this work is to describe the bacterial communities inhabiting the gastric content (GC) of preterm neonates. For that purpose, GC samples were collected weekly from a total of 13 preterm neonates during their first month of life within their hospital stay. Samples were analyzed by using both culture-dependent and -independent techniques. The former allowed the isolation of bacteria belonging mainly to the genera Enterococcus, Staphylococcus, Streptococcus, Serratia, Klebsiella, and Escherichia. The cultured dominant species in the GC samples during all the hospitalization period were Enterococcus faecalis and Staphylococcus epidermidis. Multilocus sequence typing (MLST) analysis revealed the presence of high-risk clonal complexes associated with the hospital environment, which may colonize enteral feeding tubes. Similarly, the 16S rRNA sequencing showed that Streptococcus, Staphylococcus, Lactobacillus, Enterococcus, Corynebacterium, and Propionibacterium were the dominant genera present at 75% of the gastric samples. However, the genera Serratia, Klebsiella, and Streptococcus were the most abundant. Own mother's milk (OMM) and donor milk (DM) were collected after their pass through the external feeding tubes to assess their bacterial content. OMM and DM had a similar bacterial pattern to GC. Based on these data, the GC of preterm neonates is dominated by Proteobacteria and Firmicutes and harbors high-risk bacterial clones, which may colonize enteral feeding tubes, and therefore the feeds that pass through them.

A microbiota-centric view of diseases of the upper gastrointestinal tract

The distinctive anatomy and physiology of the upper gastrointestinal tract and the difficulty of obtaining samples led to the theory that it was bacteria free. However, multiomics studies are indicating otherwise. Although influenced by both oral and gastric bacteria, the resident microbial ecosystem in the oesophagus is dominated by Streptococcus. A shift from Gram-positive to Gram-negative bacteria occurs in oesophagitis and Barrett's oesophagus, and this shift might be involved in the pathogenesis of oesophageal adenocarcinoma. The gastric microenvironment is populated by microbial communities mainly of the Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria phyla and species of the Lactobacillus, Streptococcus, and Propionibacterium genera. The composition of gastric microbiota is highly dynamic, and is influenced by acid suppression, gastric inflammation, and Helicobacter pylori. Duodenal microbes are also implicated in the onset and outcome of coeliac disease. Bacteria of the genera Bacteroides, Clostridium, and Staphylococcus dominate the duodenal flora in active coeliac disease whereas lactobacilli and bifidobacteria decrease. Although knowledge of the composition of the microbiota of the upper gastrointestinal tract has advanced substantially, this information is far from being translated to the clinical setting. In this Review, we assess the data related to the potential contribution of microbes to the susceptibility for and pathogenesis of upper gastrointestinal diseases.

Characterization of Gastric Microbiota in Twins

Contribution of host genetic backgrounds in the development of gastric microbiota has not been clearly defined. This study was aimed to characterize the biodiversity, structure and composition of gastric microbiota among twins. A total of four pairs of twins and eight unrelated individuals were enrolled in the study. Antral biopsies were obtained during endoscopy. The bacterial 16S rRNA gene was amplified and pyrosequenced. Sequences were analyzed for the composition, structure, and α and β diversities of gastric microbiota. Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Fusobacteria were the most predominant phyla of gastric microbiota. Each individual, twins as well as unrelated individuals, harbored a microbiota of distinct composition. There was no evidence of additional similarity in the richness and evenness of gastric microbiota among co-twins as compared to unrelated individuals. Calculations of θ_YC and PCoA demonstrated that the structure similarity of gastric microbial community between co-twins did not increase compared to unrelated individuals. In contrast, the structure of microbiota was altered enormously by Helicobacter pylori infection. These results suggest that host genetic backgrounds had little effect in shaping the gastric microbiota. This property of gastric microbiota could facilitate the studies discerning the role of microbiota from genetic grounds in the pathogenesis.

Effects of Proton Pump Inhibitors on the Gastric Mucosa-Associated Microbiota in Dyspeptic Patients

Besides being part of anti-Helicobacter pylori treatment regimens, proton pump inhibitors (PPIs) are increasingly being used to treat dyspepsia. However, little is known about the effects of PPIs on the human gastric microbiota, especially those related to H. pylori infection. The goal of this study was to characterize the stomach microbial communities in patients with dyspepsia and to investigate their relationships with PPI use and H. pylori status. Using 16S rRNA gene pyrosequencing, we analyzed the mucosa-associated microbial populations of 24 patients, of whom 12 were treated with the PPI omeprazole and 9 (5 treated and 4 untreated) were positive for H. pylori infection. The Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria, and Actinobacteria phyla accounted for 98% of all of the sequences, with Helicobacter, Streptococcus, and Prevotella ranking among the 10 most abundant genera. H. pylori infection or PPI treatment did not significantly influence gastric microbial species composition in dyspeptic patients. Principal-coordinate analysis of weighted UniFrac distances in these communities revealed clear but significant separation according to H. pylori status only. However, in PPI-treated patients, Firmicutes, particularly Streptococcaceae, were significantly increased in relative abundance compared to those in untreated patients. Consistently, Streptococcus was also found to significantly increase in relation to PPI treatment, and this increase seemed to occur independently of H. pylori infection. Our results suggest that Streptococcus may be a key indicator of PPI-induced gastric microbial composition changes in dyspeptic patients. Whether the gastric microbiota alteration contributes to dyspepsia needs further investigation.

IMPORTANCE

Although PPIs have become a popular treatment choice, a growing number of dyspeptic patients may be treated unnecessarily. We found that patients treated with omeprazole showed gastric microbial communities that were different from those of untreated patients. These differences regarded the abundances of specific taxa. By understanding the relationships between PPIs and members of the gastric microbiota, it will be possible to envisage new strategies for better managing patients with dyspepsia.

Bacterial overgrowth and diversification of microbiota in gastric cancer

OBJECTIVE

Microbiota is potentially linked to the development of cancer. However, the features of microbiota in gastric cancer remain unclear. The aim of this study was to characterize the gastric microbiota in cancer.

METHODS

A total of 315 patients, including 212 patients with chronic gastritis and 103 patients with gastric cancer, were enrolled in the study. The bacterial load of gastric mucosa was determined using quantitative PCR. To analyze the biodiversity, structure, and composition of microbiota, amplicons of the 16S rRNA gene from 12 patients were pyrosequenced. The sequences were processed and subsequently analyzed.

RESULTS

The amount of bacteria in gastric mucosa was estimated to be 6.9×10 per gram tissue on average. It was higher in Helicobacter pylori-infected patients (7.80±0.71) compared with those uninfected (7.59±0.57, P=0.005). An increased bacterial load up to 7.85±0.70 was detected in gastric cancer compared with chronic gastritis (P=0.001). The unweighted principal coordinate analysis showed that the structure of microbiota in gastric cancer was more diversified. Five genera of bacteria with potential cancer-promoting activities were enriched in gastric cancer. The weighted principal coordinate analysis showed that the presence of Helicobacter pylori markedly altered the structure of microbiota, but had little influence on the relative proportions of the other members in the microbiota.

CONCLUSION

Findings from this study indicated an altered microbiota in gastric cancer with increased quantity of bacteria, diversified microbial communities, and enrichment of bacteria with potential cancer-promoting activities. These alterations could contribute toward the gastric carcinogenesis.

Role of Helicobacter pylori infection in pathogenesis of gastric carcinoma

Gastric cancer (GC) is one of the most common carcinoma and the second leading cause of cancer-related deaths worldwide. Helicobacter pylori (H. pylori) infection causes a series of precancerous lesions like gastritis, atrophy, intestinal metaplasia and dysplasia, and is the strongest known risk factor for GC, as supported by epidemiological, preclinical and clinical studies. However, the mechanism of H. pylori developing gastric carcinoma has not been well defined. Among infected individuals, approximately 10% develop severe gastric lesions such as peptic ulcer disease, 1%-3% progresses to GC. The outcomes of H. pylori infection are determined by bacterial virulence, genetic polymorphism of hosts as well as environmental factors. It is important to gain further understanding of the pathogenesis of H. pylori infection for developing more effective treatments for this common but deadly malignancy. The recent findings on the bacterial virulence factors, effects of H. pylori on epithelial cells, genetic polymorphism of both the bacterium and its host, and the environmental factors for GC are discussed with focus on the role of H. pylori in gastric carcinogenesis in this review.

Association between the gut microbiota and diet: Fetal life, early childhood, and further life

Gut microbiota establishment and further microbiota shifts are very important for maintaining host health throughout life. There are some factors, including genetics, the mother's health and diet, delivery mode, breast or formula feeding, that may influence the gut microbiota. By the end of approximately the first 3 y of life, the gut microbiota becomes an adult-like stable system. Once established, 60 to 70% of the microbiota composition remains stable throughout life, but 30 to 40% can be altered by changes in the diet and other factors such as physical activity, lifestyle, bacterial infections, and antibiotic or surgical treatment. Diet-related factors that influence the gut microbiota in people of all ages are of great interest. Nutrition may have therapeutic success in gut microbiota correction. This review describes current evidence concerning the links between gut microbiota composition and dietary patterns throughout life.

Changes in gastric microbiota induced by Helicobacter pylori infection and preventive effects of Lactobacillus plantarum ZDY 2013 against such infection

Helicobacter pylori is a gram-negative pathogen linked to gastric ulcers and stomach cancer. Gastric microbiota might play an essential role in the pathogenesis of these stomach diseases. In this study, we investigated the preventive effect of a probiotic candidate Lactobacillus plantarum ZDY 2013 as a protective agent against the gastric mucosal inflammation and alteration of gastric microbiota induced by H. pylori infection in a mouse model. Prior to infection, mice were pretreated with or without 400 µL of L. plantarum ZDY 2013 at a concentration of 10(9) cfu/mL per mouse. At 6 wk postinfection, gastric mucosal immune response and alteration in gastric microbiota mice were examined by quantitative real-time PCR and high-throughput 16S rRNA gene amplicon sequencing, respectively. The results showed that L. plantarum ZDY 2013 pretreatment prevented increase in inflammatory cytokines (e.g., IL-1β and IFN-γ) and inflammatory cell infiltration in gastric lamina propria induced by H. pylori infection. Weighted UniFrac principal coordinate analysis showed that L. plantarum ZDY 2013 pretreatment prevented the alteration in gastric microbiota post-H. pylori infection. Linear discriminant analysis coupled with effect size identified 22 bacterial taxa (e.g., Pasteurellaceae, Erysipelotrichaceae, Halomonadaceae, Helicobacteraceae, and Spirochaetaceae) that overgrew in the gastric microbiota of H. pylori-infected mice, and most of them belonged to the Proteobacteria phylum. Lactobacillus plantarum ZDY 2013 pretreatment prevented this alteration; only 6 taxa (e.g., Lachnospiraceae, Ruminococcaceae, and Clostridiaceae), mainly from the taxa of Firmicutes and Bacteroidetes, were dominant in the gastric microbiota of the L. plantarum ZDY 2013 pretreated mice. Administration of L. plantarum ZDY 2013 for 3 wk led to increase in several bacterial taxa (e.g., Rikenella, Staphylococcus, Bifidobacterium), although a nonsignificant alteration was found in the gastric microbiota. Overall, this study demonstrated that L. plantarum ZDY 2013 pretreatment played an important role in preventing gastric mucosal inflammation and gastric microbiota alteration induced by H. pylori infection, and the selective modulation in gastric microbiota posed by this intervention suggested that targeting gastric microbiota through oral administration of probiotics might be an alternative strategy to prevent H. pylori infection.

The human gastric microbiota: Is it time to rethink the pathogenesis of stomach diseases?

INTRODUCTION

Although long thought to be a sterile organ, due to its acid production, the human stomach holds a core microbiome.

AIM

To provide an update of findings related to gastric microbiota and its link with gastric diseases.

METHODS

We conducted a systematic review of the literature.

RESULTS

The development of culture-independent methods facilitated the identification of many bacteria. Five major phyla have been detected in the stomach: Firmicutes, Bacteroidites, Actinobacteria, Fusobacteria and Proteobacteria. At the genera level, the healthy human stomach is dominated by Prevotella, Streptococcus, Veillonella, Rothia and Haemophilus; however, the composition of the gastric microbiota is dynamic and affected by such factors as diet, drugs and diseases. The interaction between the pre-existing gastric microbiota and Helicobacter pylori infection might influence an individual's risk of gastric disease, including gastric cancer.

CONCLUSIONS

The maintenance of bacterial homeostasis could be essential for the stomach's health and highlights the chance for therapeutic interventions targeting the gastric microbiota, even if gastric pH, peristalsis and the mucus layer may prevent bacteria colonization; and the definition of gastric microbiota of the healthy stomach is still an ongoing challenging task.

The Microbiome and Sustainable Healthcare

Increasing prevalences, morbidity, premature mortality and medical needs associated with non-communicable diseases and conditions (NCDs) have reached epidemic proportions and placed a major drain on healthcare systems and global economies. Added to this are the challenges presented by overuse of antibiotics and increased antibiotic resistance. Solutions are needed that can address the challenges of NCDs and increasing antibiotic resistance, maximize preventative measures, and balance healthcare needs with available services and economic realities. Microbiome management including microbiota seeding, feeding, and rebiosis appears likely to be a core component of a path toward sustainable healthcare. Recent findings indicate that: (1) humans are mostly microbial (in terms of numbers of cells and genes); (2) immune dysfunction and misregulated inflammation are pivotal in the majority of NCDs; (3) microbiome status affects early immune education and risk of NCDs, and (4) microbiome status affects the risk of certain infections. Management of the microbiome to reduce later-life health risk and/or to treat emerging NCDs, to spare antibiotic use and to reduce the risk of recurrent infections may provide a more effective healthcare strategy across the life course particularly when a personalized medicine approach is considered. This review will examine the potential for microbiome management to contribute to sustainable healthcare.