Non-Helicobacter pylori bacterial flora during acid-suppressive therapy: differential findings in gastric juice and gastric mucosa

Interactions between Dietary Antioxidants, Dietary Fiber and the Gut Microbiome: Their Putative Role in Inflammation and Cancer

The intricate relationship between the gastrointestinal (GI) microbiome and the progression of chronic non-communicable diseases underscores the significance of developing strategies to modulate the GI microbiota for promoting human health. The administration of probiotics and prebiotics represents a good strategy that enhances the population of beneficial bacteria in the intestinal lumen post-consumption, which has a positive impact on human health. In addition, dietary fibers serve as a significant energy source for bacteria inhabiting the cecum and colon. Research articles and reviews sourced from various global databases were systematically analyzed using specific phrases and keywords to investigate these relationships. There is a clear association between dietary fiber intake and improved colon function, gut motility, and reduced colorectal cancer (CRC) risk. Moreover, the state of health is reflected in the reciprocal and bidirectional relationships among food, dietary antioxidants, inflammation, and body composition. They are known for their antioxidant properties and their ability to inhibit angiogenesis, metastasis, and cell proliferation. Additionally, they promote cell survival, modulate immune and inflammatory responses, and inactivate pro-carcinogens. These actions collectively contribute to their role in cancer prevention. In different investigations, antioxidant supplements containing vitamins have been shown to lower the risk of specific cancer types. In contrast, some evidence suggests that taking antioxidant supplements can increase the risk of developing cancer. Ultimately, collaborative efforts among immunologists, clinicians, nutritionists, and dietitians are imperative for designing well-structured nutritional trials to corroborate the clinical efficacy of dietary therapy in managing inflammation and preventing carcinogenesis. This review seeks to explore the interrelationships among dietary antioxidants, dietary fiber, and the gut microbiome, with a particular focus on their potential implications in inflammation and cancer.

A Novel Characteristic Gastric Mucus Named "Web-like Mucus" Potentially Induced by Vonoprazan

Background: In the absence of Helicobacter pylori (HP) infection, a characteristic gastric mucus adhesion may appear during the use of vonoprazan. We named this novel characteristic mucus "web-like mucus" (WLM). This study aimed to determine the incidence and risk factors for WLM. Methods: Between January 2017 and January 2022, 5665 patients were enrolled in this study. The patients were divided into a proton-pump inhibitor (PPI)-prescribed group (n = 2000), a vonoprazan-prescribed group (n = 268), and a no-PPI/vonoprazan-prescribed (n = 3397) group, and the presence of WLM was examined. After excluding four patients with autoimmune gastritis, the remaining 264 patients in the vonoprazan group were divided into WLM and non-WLM groups, and their clinical features were analyzed. Results: A total of 55 (21%) patients had WLM, all in the vonoprazan-prescribed group. There were no significant differences in factors such as, sex, age, chronic kidney disease, diabetes mellitus, HP eradication history, smoking, or alcohol consumption between the WLM and non-WLM groups. The median duration from the start of vonoprazan administration to the endoscopic detection of WLM was 2 (1-24) months. Conclusions: WLM appears to be a characteristic feature in patients treated with vonoprazan.

Intragastric bacterial infection and endoscopic findings in Helicobacter pylori-negative patients

In the present study, the authors examined the association between gastric bacterial infection and gastric endoscopic findings in Helicobacter pylori (H. pylori)-negative patients. The subjects were 105 H. pylori-negative patients. The mean age was 72.8 ± 9.1 years. Endoscopy and gastric juice culture were performed. The presence or absence of endoscopic findings was checked according to the Kyoto classification of gastritis. Culture was positive in 69 patients (65.7%), with Streptococcus α-hemolytic being the most common (51 patients), followed by Neisseria sp. (43 patients). According to the univariate analysis, there was a significant difference between the results of culture and background factors in the use of gastric antisecretory drugs and between the results of culture and various endoscopic findings in atrophic gastritis, intestinal metaplasia, regular arrangement of collecting venule, mucosal swelling, sticky mucus, hyperplastic polyps, hematin, and gastric cobblestone-like lesions. Furthermore, multivariate analysis revealed significant differences in background factors such as the use of gastric antisecretory drugs and endoscopic findings only in patients with mucosal swelling. Endoscopic findings of non-H. pylori bacteria-positive gastritis differed from endoscopic findings of H. pylori-infected gastritis in several respects. In conclusion, our results suggest that non-H. pylori bacteria may infect the stomach and cause gastric inflammation, especially in patients who long term use gastric antisecretory drugs.

Proton pump inhibitor-induced gut dysbiosis and immunomodulation: current knowledge and potential restoration by probiotics

Proton pump inhibitors (PPIs) are the most commonly prescribed drugs for the treatment of non-erosive reflux disease (NERD), ulcers associated with non-steroidal anti-inflammatory drugs (NSAIDs), esophagitis, peptic ulcer disease (PUD), Zollinger-Ellison syndrome (ZES), gastroesophageal reflux disease (GERD), non-ulcer dyspepsia, and Helicobacter pylori eradication therapy. The drugs have the effect of inhibiting acid production in the stomach. According to research, PPIs can affect the composition of gut microbiota and modulate the immune response. Recently, there has been a problem with the over-prescription of such drugs. Although PPIs do not have many side effects, their long-term use can contribute to small intestinal bacterial overgrowth (SIBO) or C. difficile and other intestinal infections. Probiotic supplementation during PPIs therapy may provide some hope in the reduction of emerging therapy side effects. This review aims to present the most important effects of long-term PPI use and provides critical insights into the role of probiotic intervention in PPI therapy.

Microbial composition of tumorous and adjacent gastric tissue is associated with prognosis of gastric cancer

Helicobacter pylori (H. pylori) infection has been considered as the main causal factor in gastric carcinogenesis, but other bacterial species may also play an important role in pathophysiology of gastric cancer. The aim of the study was to explore the link between gastric cancer prognosis and the mucosal microbial community in tumorous and adjacent gastric tissue. The bacterial profile was analysed using 16S sequencing (V1-V2 region). Microbial differences were mostly characterized by lower relative abundances of H. pylori in tumorous gastric tissues. Bacterial community and outcome data analysis revealed the genus Fusobacterium and Prevotella significantly associated with worse overall survival in gastric cancer patients. In particular, Fusobacterium was associated with significant increase in hazard ratio in both univariable and multivariable analysis and independently validated using TCMA data. Phylogenetic biodiversity of Fusobacterium species in the stomach revealed F. periodonticum as the most prevalent in healthy subjects, while F. nucleatum was most abundant in patients with gastric cancer. Bacterial community network analysis in gastric cancer suggests substantial complexity and a strong interplay between F. nucleatum and Prevotella. In summary, mucosal microbial community in the stomach was associated with worse overall survival in gastric cancer patients. Strongest negative impact on prognosis was linked to the abundance of F. nucleatum in tumorous specimens, suggesting its translational relevance in management of gastric cancer patients.

Dynamic variations of the gastric microbiota: Key therapeutic points in the reversal of Correa's cascade

Correa's cascade is a dynamic process in the development of intestinal-type gastric cancer (GC), and its pathological features, gastric microbiota and interactions between microorganisms and their hosts vary at different developmental stages. The characteristics of cells, tissues and gastric microbiota before or after key therapeutic points are critical for monitoring malignant transformation and early tumour reversal. This review summarises the pathological features of gastric mucosa, characteristics of gastric microbiota, specific microbial markers, microbe-microbe interactions and microbe-host interactions at different stages in Correa's cascade. The markers related to each Correa's cascade point were analysed in detail. We attempted to identify key therapeutic points for early cancer reversal and provide a novel approach to reduce the incidence of GC and improve precise treatment.

Intraprocedural gastric juice analysis as compared to rapid urease test for real-time detection of Helicobacter pylori

BACKGROUND

Endofaster is an innovative technology that can be combined with upper gastrointestinal endoscopy (UGE) to perform gastric juice analysis and real-time detection of Helicobacter pylori (H. pylori).

AIM

To assess the diagnostic performance of this technology and its impact on the management of H. pylori in the real-life clinical setting.

METHODS

Patients undergoing routine UGE were prospectively recruited. Biopsies were taken to assess gastric histology according to the updated Sydney system and for rapid urease test (RUT). Gastric juice sampling and analysis was performed using the Endofaster, and the diagnosis of H. pylori was based on real-time ammonium measurements. Histological detection of H. pylori served as the diagnostic gold standard for comparing Endofaster-based H. pylori diagnosis with RUT-based H. pylori detection.

RESULTS

A total of 198 patients were prospectively enrolled in an H. pylori diagnostic study by Endofaster-based gastric juice analysis (EGJA) during the UGE. Biopsies for RUT and histological assessment were performed on 161 patients (82 men and 79 women, mean age 54.8 ± 19.2 years). H. pylori infection was detected by histology in 47 (29.2%) patients. Overall, the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value (NPV) for H. pylori diagnosis by EGJA were 91.5%, 93.0%, 92.6%, 84.3%, and 96.4%, respectively. In patients on treatment with proton pump inhibitors, diagnostic sensitivity was reduced by 27.3%, while specificity and NPV were unaffected. EGJA and RUT were comparable in diagnostic performance and highly concordant in H. pylori detection (κ-value = 0.85).

CONCLUSION

Endofaster allows for rapid and highly accurate detection of H. pylori during gastroscopy. This may guide taking additional biopsies for antibiotic susceptibility testing during the same procedure and then selecting an individually tailored eradication regimen.

Intraprocedural gastric juice analysis as compared to rapid urease test for real-time detection of Helicobacter pylori

BACKGROUND

Endofaster is an innovative technology that can be combined with upper gastrointestinal endoscopy (UGE) to perform gastric juice analysis and real-time detection of Helicobacter pylori (H. pylori).

AIM

To assess the diagnostic performance of this technology and its impact on the management of H. pylori in the real-life clinical setting.

METHODS

Patients undergoing routine UGE were prospectively recruited. Biopsies were taken to assess gastric histology according to the updated Sydney system and for rapid urease test (RUT). Gastric juice sampling and analysis was performed using the Endofaster, and the diagnosis of H. pylori was based on real-time ammonium measurements. Histological detection of H. pylori served as the diagnostic gold standard for comparing Endofaster-based H. pylori diagnosis with RUT-based H. pylori detection.

RESULTS

A total of 198 patients were prospectively enrolled in an H. pylori diagnostic study by Endofaster-based gastric juice analysis (EGJA) during the UGE. Biopsies for RUT and histological assessment were performed on 161 patients (82 men and 79 women, mean age 54.8 ± 19.2 years). H. pylori infection was detected by histology in 47 (29.2%) patients. Overall, the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value (NPV) for H. pylori diagnosis by EGJA were 91.5%, 93.0%, 92.6%, 84.3%, and 96.4%, respectively. In patients on treatment with proton pump inhibitors, diagnostic sensitivity was reduced by 27.3%, while specificity and NPV were unaffected. EGJA and RUT were comparable in diagnostic performance and highly concordant in H. pylori detection (κ-value = 0.85).

CONCLUSION

Endofaster allows for rapid and highly accurate detection of H. pylori during gastroscopy. This may guide taking additional biopsies for antibiotic susceptibility testing during the same procedure and then selecting an individually tailored eradication regimen.

Use of proton pump inhibitors for the risk of gastric cancer

BACKGROUND

This study aimed to systematically analyze the association between long-term use of proton pump inhibitors (PPIs) and the risk of gastric cancer (GC).

METHODS

We performed a systematic search of articles on the relationship between long-term use of PPIs and the risk of GC from PubMed and EMBASE. We calculated the pooled odds ratio of GC in PPI users compared to non-PPI users using random-effects models.

RESULTS

This meta-analysis included 18 studies from 20 different databases with 4348,905 patients enrolled. In the random effects model, we found that an increased risk of GC among PPI users (OR = 1.94; 95% CI [1.43, 2.64]). The long-term use of PPIs compared with histamine-2 receptor antagonist users did not increase the risk of GC (OR = 1.65; 95% CI [0.92, 2.97]). Stratified analysis showed that PPI users had a significantly increased risk of noncardia GC (OR = 2.53; 95% CI [2.03, 3.15]), but had a relatively small relationship with the risk of gastric cardia cancer. (OR = 1.79; 95% CI [1.06, 3.03]). With the extension of PPI use time, the estimated risk value decreases (<1 year: OR = 6.33, 95% CI [3.76, 10.65]; 1-3 years: OR = 1.82, 95% CI [1.30, 2.55]; >3 years: OR = 1.25, 95% CI [1.00, 1.56]). Despite Helicobacter pylori eradication, the long-term use of PPIs did not alter the increased risk of GC (OR = 2.29; 95% CI [1.57, 3.33]).

CONCLUSION

Our meta-analysis found that PPI use may be associated with an increased risk of GC. Further research on the causal relationship between these factors is necessary.

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.

Effect of a Proton Pump Inhibitor on the Duodenum Microbiome of Gastric Ulcer Patients

The gut microbiota are regarded as a functional organ that plays a substantial role in human health and disease. Proton pump inhibitors (PPIs) are widely used in medicine but can induce changes in the overall gut microbiome and cause disease-associated dysbiosis. The microbiome of the duodenum has not been sufficiently studied, and the effects of PPIs on the duodenal microbiome are poorly understood. In this study, we investigated the effect of PPI administration on duodenum microbiota in patients with a gastric ulcer. A total of 12 gastric ulcer patients were included, and PPI (Ilaprazole, Noltec^®, 10 mg) was prescribed in all patients for 4 weeks. A total of 17 samples from the second portion of the duodenum were analyzed. Microbiome compositions were assessed by sequencing the V3–V4 region of the 16s rRNA gene (Miseq). Changes in microbiota compositions after 4 weeks of PPI treatment were analyzed. a-Diversity was higher after PPI treatment (p = 0.02, at Chao1 index), and β-diversity was significantly different after treatment (p = 0.007). Welch’s t-test was used to investigate changes in phyla, genus, and species level, and the abundance of Akkermansia muciniphila, belonging to the phylum Verrucomicrobia, and Porphyromonas endodontalis, belonging to the phylum Bacteroidetes, was significantly increased after treatment (p = 0.044 and 0.05). PPI administration appears to induce duodenal microbiome dysbiosis while healing gastric ulcers. Further large-scale studies on the effects of PPIs on the duodenal microbiome are required.

Association of proton pump inhibitor use with survival outcomes in cancer patients treated with immune checkpoint inhibitors: a systematic review and meta-analysis

Background:

Proton pump inhibitors (PPIs) have been shown to regulate the gut microbiome and affect the response to immune checkpoint inhibitors (ICIs). Contradictory results on survival have been observed in patients concomitantly treated with ICIs and PPIs. We performed a systematic review and meta-analysis to determine the association between PPI use and survival outcomes in ICI-treated cancer patients.

Methods:

EMBASE, MEDLINE/PubMed, Cochrane Library databases, and major oncology conference proceedings were searched. Studies comparing overall survival (OS) and progression-free survival (PFS) between PPI-treated and PPI-free groups of ICI-treated cancer patients were included. Data regarding study and patient characteristics, ICI and PPI treatments, and survival outcomes were extracted. Hazard ratios (HRs) with 95% confidence interval (CI) were pooled using random effects models. Subgroup meta-analyses and meta-regressions were performed to explore possible factors of heterogeneity among the studies.

Results:

A total of 33 studies were included, comprising 7383 ICI- and PPI-treated patients and 8574 ICI-treated and PPI-free patients. The pooled HR was 1.31 (95% CI, 1.19–1.44; p < 0.001) for OS and 1.30 (95% CI, 1.17–1.46; p < 0.001) for PFS, indicating a significant negative association between PPI use and survival in ICI-treated patients. Subgroup meta-analyses by factors including cancer type, ICI type, and time window of PPI use revealed that ICI and PPI use impacted survival in patients with non-small cell lung or urothelial cancer, patients treated with anti-PD-1/PD-L1 antibodies, and patients receiving PPI as baseline treatment or 60 days before ICI treatment initiation.

Conclusions:

PPI use in patients treated with ICIs was associated with shorter OS and PFS, especially in several specific subgroups of cancer patients. PPIs should be strictly controlled and appear to not impact survival if given temporarily after ICI initiation. These observations could provide the basis for clinical guidelines for concomitant PPI and ICI use.

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.

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.

Association of Common Medications and the Risk of Early-Onset Gastric Cancer: A Population-Based Matched Study

BACKGROUND

Early-onset gastric cancer (EOGC, age ≤ 60 years at diagnosis) now comprises >30% of new gastric cancers in the United States. It is hypothesized that chronic acid suppression with proton-pump inhibitors (PPIs) may promote tumorigenesis, while other medications including statins, nonsteroidal anti-inflammatory drugs (NSAIDs), metformin, and cyclooxygenase-2 (COX-2) inhibitors have been proposed as protective. We aimed to assess for an association between use of the aforementioned commonly prescribed medications and EOGC development.

METHODS

We used a population-based medical record linkage system, to identify cases of EOGC in Olmsted County, Minnesota, between January 1, 1995, and December 31, 2020. Patients were matched 1 : 1 with controls based on age at diagnosis, sex, smoking status, and body mass index (BMI). Conditional logistic regression was used to examine associations with the odds of EOGC development.

RESULTS

Ninety-six cases of EOGC were identified during the study period. On both univariate and multivariate regression analysis, there was no significant association between use of PPIs, statins, NSAIDs, or metformin and EOGC development. In a final multivariable model, there was a significant reduction in odds of EOGC with COX-2 inhibitor use for six months or more prior to cancer diagnosis (OR = 0.39, 95% CI 0.16-0.94).

CONCLUSION

In this retrospective, population-based study of individuals in Olmsted County, MN, we found significantly reduced odds of EOGC development associated with COX-2 inhibitor use for six months or more prior to diagnosis, but no association between EOGC development and use of PPIs and other commonly prescribed medications.

Association between proton pump inhibitor use and gastric cancer: a population-based cohort study using two different types of nationwide databases in Korea

OBJECTIVE

The association between proton pump inhibitor (PPI) use and gastric cancer related to Helicobacter pylori eradication has not been fully investigated in geographical regions with high risk of gastric cancer. We aimed to evaluate the association between PPIs and gastric cancer in Korea.

DESIGN

This study analysed the original and common data model versions of the Korean National Health Insurance Service database from 2002 to 2013. We compared the incidence rates of gastric cancer after 1-year drug exposure, between new users of PPIs and other drugs excluding PPIs, by Cox proportional hazards model. We also analysed the incidence of gastric cancer among PPI users after H. pylori eradication.

RESULTS

The analysis included 11 741 patients in matched PPI and non-PPI cohorts after large-scale propensity score matching. During a median follow-up of 4.3 years, PPI use was associated with a 2.37-fold increased incidence of gastric cancer (PPI≥30 days vs non-PPI; 118/51 813 person-years vs 40/49 729 person-years; HR 2.37, 95% CI 1.56 to 3.68, p=0.001). The incidence rates of gastric cancer showed an increasing trend parallel to the duration of PPI use. In H. pylori-eradicated subjects, the incidence of gastric cancer was significantly associated with PPI use over 180 days compared with the non-PPI group (PPI≥180 days vs non-PPI; 30/12 470 person-years vs 9/7814 person-years; HR 2.22, 95% CI 1.05 to 4.67, p=0.036).

CONCLUSION

PPI use was associated with gastric cancer, regardless of H. pylori eradication status. Long-term PPIs should be used with caution in high-risk regions for gastric cancer.

Interplay and cooperation of Helicobacter pylori and gut microbiota in gastric carcinogenesis

Chronic Helicobacter pylori infection is a critical risk factor for gastric cancer (GC). However, only 1–3 % of people with H. pylori develop GC. In gastric carcinogenesis, non-H. pylori bacteria in the stomach might interact with H. pylori. Bacterial dysbiosis in the stomach can strengthen gastric neoplasia development via generating tumor-promoting metabolites, DNA damaging, suppressing antitumor immunity, and activating oncogenic signaling pathways. Other bacterial species may generate short-chain fatty acids like butyrate that may inhibit carcinogenesis and inflammation in the human stomach. The present article aimed at providing a comprehensive overview of the effects of gut microbiota and H. pylori on the development of GC. Next, the potential mechanisms of intestinal microbiota were discussed in gastric carcinogenesis. We also disserted the complicated interactions between H. pylori, intestinal microbiota, and host in gastric carcinogenesis, thus helping us to design new strategies for preventing, diagnosing, and treating GC.

Proton Pump Inhibitors and Gastric Cancer

Concerns have been raised regarding the long-term use of proton pump inhibitors (PPIs) as an important risk factor for gastric cancer in clinical practice. PPIs can cause hypergastrinemia at clinical doses, and hypergastrinemia has been reported to induce malignant neoplasms in the stomach in previous animal studies. In humans, the proliferation of enterochromaffin-like (ECL) cells induced by hypergastrinemia is suspected as a potential mechanism of gastric cancer. Meanwhile, persistent Helicobacter pylori (H. pylori) infection causes gastric atrophic change, which itself is a major cause of gastric cancer, and it can further increase the risk of gastric cancer by strengthening corpus atrophy through interaction with PPIs. Recent epidemiologic studies have reported an important link between long-term PPI intake and gastric cancer risk even after successful eradication of H. pylori. However, due to the methodological limitations of observational clinical studies, the causal relationship is still not clear, and a recent big data-based study reported that long-term PPI use was not related to gastric cancer incidence. Taken together, despite the potential detrimental effects of PPIs, it is currently difficult to draw a definite conclusion about its association with gastric cancer. To minimize the possibility of gastric cancer in H. pylori-infected patients or precancerous lesions in long-term PPI users, long-term PPI administration should be limited to the minimum effective dose, and antibacterial treatment for H. pylori should be considered.

Gastric Microbiota in a Low-Helicobacter pylori Prevalence General Population and Their Associations With Gastric Lesions

INTRODUCTION:

Non–Helicobacter pylori microbiota might account for some cases with unexplained chronic gastritis that may in a minority eventually progress to gastric cancer through the Correa cascade. We characterized gastric microbiota by describing the normal stomach, compared it with early precancerous lesions and other disease states, and assessed whether H. pylori status affects bacterial diversity.

METHODS:

In a population-based study of those with and without gastrointestinal symptoms, cytology brush samples were collected during endoscopy from 316 individuals. Mucosal status was classified as normal mucosa (171), nonatrophic H. pylori gastritis (33), atrophic gastritis (12), or antral chemical gastritis (61). The 16S rRNA gene sequencing and analysis were performed to characterize the microbiota.

RESULTS:

Microbiota in atrophic gastritis and nonatrophic H. pylori gastritis stomachs were dysbiotic and differed from those in the normal stomach (P = 0.001). The normal stomach had the highest microbial diversity, followed by antral chemical gastritis. The atrophic gastritis and chronic H. pylori gastritis groups had the lowest diversity, a difference that was statistically significant (P = 0.01). Besides H. pylori, non–H. pylori bacteria accounted for group differences. Microbial network analysis showed that the normal group network was most highly connected, whereas the H. pylori gastritis group had the lowest connection. We found an increasing positive co-occurrence of oral bacteria in the stomach because samples deviated from the normal network, some of which were pathogens. The H. pylori–negative group had the highest microbial diversity (Shannon index) compared with the H. pylori–positive group (P = 0.001).

DISCUSSION:

In this low–H. pylori prevalence general population, the gastric mucosal microbiota of the normal stomach differed significantly from those with nonatrophic or atrophic gastritis. There was an increasing abundance of pathogenic bacteria from the normal state to early precancerous states.

Integrating microbiome, transcriptome and metabolome data to investigate gastric disease pathogenesis: a concise review

Microbiome, the study of microbial communities in specific environments, has developed significantly since the Human Microbiome Project began. Microbiomes have been associated with changes within environmental niches and the development of various diseases. The development of high-throughput technology such as next-generation sequencing has also allowed us to perform transcriptome studies, which provide accurate functional profiling data. Metabolome studies, which analyse the metabolites found in the environment, are the most direct environmental condition indicator. Although each dataset provides valuable information on its own, the integration of multiple datasets provides a deeper understanding of the relationship between the host, agent and environment. Therefore, network analysis using multiple datasets might give a clearer understanding of disease pathogenesis.

The Related Study on the Pathogenesis of Gastrointestinal Diseases in Gastrointestinal Flora and the Risk of Gastric Ulcer Carcinogenesis

Gastrointestinal diseases are common diseases of many kinds. The pathogenesis of gastrointestinal disease has not been fully understood. In this study with gastric mucosa specimen, among the three groups of chronic gastritis, gastric ulcer, and duodenal ulcer, there were differences of Helicobacter pylori (H. pylori), Lactobacillus, Prevotella, Clostridium, B. fragilis, and Enterobacteriaceae. There was no significant difference in Lactobacillus among chronic gastritis, gastric ulcers, and duodenal ulcers with fecal specimens, but there was a significant difference between these three groups and the gastric cancer group. Correlation analysis showed that six kinds of flora had a negative correlation with H. pylori, procalcitonin (PCT), tumor necrosis factor α (TNF-α), cluster of differentiation 4 (CD4+), cluster of differentiation 8 (CD8+), immunoglobulin G (IgG), and immunoglobulin M (IgM) were different in different gastrointestinal diseases, and PCT, TNF-α and CD8+ were positively correlated with H. pylori and negatively correlated with CD4+, IgM and IgG. Logistic regression analysis showed that age, recurrent gastric ulcer times, atrophic gastritis, and H. pylori were independent risk factors of gastric ulcer canceration. Therefore, we believe that gastrointestinal flora, especially H. pylori, plays a vital role in the pathogenesis of gastrointestinal diseases, and H. pylori is an essential risk factor for gastric ulcer carcinogenesis.

Risk of peritonitis after gastroscopy in peritoneal dialysis patients

BACKGROUND

Peritonitis is a common and serious complication of peritoneal dialysis (PD). Translocation of gut bacteria to peritoneum is an important mechanism, which may be enhanced by gastrointestinal endoscopy.

METHODS

In this retrospective observational cohort study, we identified 450 gastroscopies performed in PD patients within a single centre between 2014 and 2019. Gastroscopy-related peritonitis was defined by peritonitis within 1 week after endoscopy.

RESULTS

A total of 408 endoscopic episodes in 216 patients were analysed after excluding 42 cases with either pre-existing peritonitis before endoscopy, or concomitant biliary, small bowel or large bowel endoscopy. There were 16 episodes of peritonitis within 1 week of endoscopy (3.9%). One-quarter of cases were polymicrobial (four episodes, 25.0%). Logistic regression model showed that patient's age, number of endoscopic biopsies, and histamine-2 receptor blocker use were independently associated with peritonitis, while prior antibiotics exposure was associated with lower risk of peritonitis, odds ratio 0.23 (95% confidence interval 0.06-0.95; p = 0.04).

CONCLUSION

Peritonitis can complicate gastroscopy in PD patients and occurs more often in elderly or after repeated biopsy procedures.

Role of Bacterial and Viral Pathogens in Gastric Carcinogenesis

Gastric cancer (GC) is one of the deadliest malignancies worldwide. In contrast to many other tumor types, gastric carcinogenesis is tightly linked to infectious events. Infections with Helicobacter pylori (H. pylori) bacterium and Epstein-Barr virus (EBV) are the two most investigated risk factors for GC. These pathogens infect more than half of the world's population. Fortunately, only a small fraction of infected individuals develops GC, suggesting high complexity of tumorigenic processes in the human stomach. Recent studies suggest that the multifaceted interplay between microbial, environmental, and host genetic factors underlies gastric tumorigenesis. Many aspects of these interactions still remain unclear. In this review, we update on recent discoveries, focusing on the roles of various gastric pathogens and gastric microbiome in tumorigenesis.

Nonlinear machine learning pattern recognition and bacteria-metabolite multilayer network analysis of perturbed gastric microbiome

The stomach is inhabited by diverse microbial communities, co-existing in a dynamic balance. Long-term use of drugs such as proton pump inhibitors (PPIs), or bacterial infection such as Helicobacter pylori, cause significant microbial alterations. Yet, studies revealing how the commensal bacteria re-organize, due to these perturbations of the gastric environment, are in early phase and rely principally on linear techniques for multivariate analysis. Here we disclose the importance of complementing linear dimensionality reduction techniques with nonlinear ones to unveil hidden patterns that remain unseen by linear embedding. Then, we prove the advantages to complete multivariate pattern analysis with differential network analysis, to reveal mechanisms of bacterial network re-organizations which emerge from perturbations induced by a medical treatment (PPIs) or an infectious state (H. pylori). Finally, we show how to build bacteria-metabolite multilayer networks that can deepen our understanding of the metabolite pathways significantly associated to the perturbed microbial communities.

A case of phlegmonous gastritis after acute pharyngitis

We report a case of phlegmonous gastritis that followed an episode of acute pharyngitis. A 21-year-old man visited our emergency room because of intense epigastric pain. Fourteen days before the visit, he had symptoms of a sore throat and high fever. He was diagnosed with acute pharyngitis and treated with antibiotics. Although the symptoms of acute pharyngitis were relieved, epigastric pain began 5 days before the emergency visit. Computed tomography showed diffuse gastric wall thickening, and emergent esophagogastroduodenoscopy revealed diffusely spreading hyperemic mucosa with multiple erosions. He was admitted with a diagnosis of acute phlegmonous gastritis and was treated with antibiotics. The antibiotic treatment was effective and resulted in resolution of his clinical symptoms and normalized C-reactive protein concentrations. On hospital day 29, he was discharged. However, he was re-admitted because of recurrence of phlegmonous gastritis 5 days after discharge and 15 days after finishing the antibiotics. Cultures of gastric biopsies and juice were both positive for Streptococcus constellatus/milleri. Antibiotic treatment was effective, and he recovered without recurrence. A possible association between upper respiratory infections and subsequent phlegmonous gastritis has been reported, and this case supports causality. However, further studies are needed to evaluate causality and pathogenesis.

The microbiome: Composition and locations

The human body is home to a diverse and functionally important assemblage of symbiotic microbes that varies predictably over different spatial scales, both within and across body sites. The composition of these spatially distinct microbial consortia can be impacted by a variety of stochastic and deterministic forces, including dispersal from different source communities, and selection by regionally-specific host processes for the enrichment of physiologically significant taxa. In this chapter, we review the composition, function, and assembly of the healthy human gastrointestinal, skin, vaginal, and respiratory microbiomes, with special emphasis on the regional distribution of microbes throughout the gastrointestinal tract.

Precancerous lesions of the stomach, gastric cancer and hereditary gastric cancer syndromes

Gastric cancer accounts for about 6% of cancers worldwide, being the fifth most frequently diagnosed malignancy and the third leading cause of cancer related death. Gastric carcinogenesis is a multistep and multifactorial process and is the result of the complex interplay between genetic susceptibility and environmental factors. The identification of predisposing conditions and of precancerous lesions is the basis for screening programs and early stage treatment. Furthermore, although most gastric cancers are sporadic, familial clustering is observed in up to 10% of patients. Among them, hereditary cases, related to known cancer susceptibility syndromes and/or genetic causes are thought to account for 1-3% of all gastric cancers. The pathology report of gastric resections specimens therefore requires a standardized approach as well as in depth knowledge of prognostic and treatment associated factors.

Patients With Reflux Esophagitis Possess a Possible Different Oral Microbiota Compared With Healthy Controls

Background and Aim

Reflux Esophagitis (RE) is caused by a variety of factors including anatomical and functional alterations involved in the pathogenesis. Oral microbiota is influenced by many factors such as heredity, nutrition, environments and host conditions, but little is known about relationship between oral microbiota and RE. The aim of this study was to explore whether the oral microbiota is changed in patients with RE.

Methods

To clarify this correlation, fresh saliva samples from all subjects were collected and then oral microorganism diversity was analysed in 55 patients with RE and 51 controls via hypervariable tag sequencing and analyzing the V3–V4 region of the 16S rDNA gene.

Results

There was no difference found in oral microbial diversity between RE patients and healthy controls by Shannon diversity index (p=0.60) and Simpson diversity index (p= 0.38). The abundance of Proteobacteria was lower, but Bacteroidetes was higher in patients with RE at the phylum level. At the genus level the abundances of Prevotella, Veillonella, Megasphaera, Peptostreptococcus, Atopobium, Oribacterium, Eubacterium, and Lachnoanaerobaculum were increased, while Neisseria, Streptococcus, Rothia, Granulicatella, Gemella, Aggregatibacter, Treponema, Campylobacter, Filifactor, Corynebacterium, and Lactivibrio were decreased in RE patients than the controls.

Conclusions

Our study suggested oral microbial dysbiosis in patients with RE, and identified bacterial species with potential biomarker significance. Further studies are required to understand role of oral microbial dysbiosis in the pathogenesis of RE.

Use of proton pump inhibitors and histamine-2 receptor antagonists and risk of gastric cancer in two population-based studies

BACKGROUND

Studies have shown increased gastric cancer risk in users of proton pump inhibitors (PPI) and histamine-2 receptor antagonists, questioning the safety of gastric acid suppression. Therefore, we conducted a case-control study within the Scottish Primary Care Clinical Informatics Unit (PCCIU) database and a cohort study in the UK Biobank.

METHODS

In PCCIU, five controls were matched to cases diagnosed in 1999-2011, and medications were determined from GP records. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using conditional logistic regression. In the UK Biobank, medications were self-reported at cohort entry 2006-2010, and gastric cancer ascertained from cancer registries until 2014. Hazard ratios (HR) were calculated using Cox regression.

RESULTS

PCCIU contained 1119 cases and 5394 controls. UK Biobank contained 250 cases in 471,779 participants. PPI users had a higher gastric cancer risk in PCCIU and UK Biobank when applying a 1-year lag (adjusted OR = 1.49, 95% CI 1.24, 1.80; adjusted HR = 1.28, 95% CI 0.86, 1.90, respectively), but these associations were attenuated when using a 2-year lag (adjusted OR = 1.13, 95% CI 0.91, 1.40; adjusted HR = 1.15, 95% CI 0.73, 1.82, respectively).

CONCLUSIONS

Overall, we observed little consistent evidence of an increased risk of gastric cancer with PPI use.

Transient and Persistent Gastric Microbiome: Adherence of Bacteria in Gastric Cancer and Dyspeptic Patient Biopsies after Washing

Helicobacter pylori is a common colonizer of the human stomach, and long-term colonization has been related to development of atrophic gastritis, peptic ulcers and gastric cancer. The increased gastric pH caused by H. pylori colonization, treatment with antibiotics or proton pump inhibitors (PPI) may allow growth of other bacteria. Previous studies have detected non-Helicobacter bacteria in stomach biopsies, but no conclusion has been made of whether these represent a transient contamination or a persistent microbiota. The aim of this study was to evaluate the transient and persistent bacterial communities of gastric biopsies. The washed or unwashed gastric biopsies were investigated by cultivation and microbiota analysis (16S rRNA gene-targeted amplicon sequencing) for the distribution of H. pylori and other non-Helicobacter bacteria. The number of cultured non-Helicobacter bacteria decreased in the washed biopsies, suggesting that they might be a transient contamination. No significant differences in the bacterial diversity were observed in the microbiome analysis between unwashed and washed biopsies. However, the bacterial diversity in biopsies shown H. pylori-positive and H. pylori-negative were significantly different, implying that H. pylori is the major modulator of the gastric microbiome. Further large-scale studies are required to investigate the transient and persistent gastric microbiota.

Prevalence of non Helicobacter pylori gastric Helicobacters in Iranian dyspeptic patients

BACKGROUND

Non Helicobacter pylori gastric Helicobacters (NHPGHs) are associated with a range of upper gastrointestinal symptoms, histologic and endoscopic findings. For the first time in Iran, we performed a cross-sectional study in order to determine the prevalence of five species of NHPGHs in patients presenting with dyspepsia.

METHODS

The participants were divided into H. pylori-infected and NHPGH-infected groups, based on the rapid urease test, histological analysis of biopsies, and PCR assay of ureA, ureB, and ureAB genes. The study included 428 gastric biopsies form dyspeptic patients, who did not receive any treatment for H. pylori. The samples were collected and sent to the laboratory within two years. H. pylori was identified in 368 samples, which were excluded from the study. Finally, a total of 60 non-H. pylori samples were studied for NHPGH species.

RESULTS

The overall frequency of NHPGH species was 10 for H. suis (three duodenal ulcer, three gastritis, and four gastric ulcer samples), 10 for H. felis (one gastritis, three duodenal ulcer, and six gastric ulcer samples), 20 for H. salomonis (four duodenal ulcer, five gastritis, and 11 gastric ulcer samples), 13 for H. heilmannii (three gastritis, five duodenal ulcer, and five gastric ulcer samples), and 7 for H. bizzozeronii (zero gastric ulcer, two duodenal ulcer, and five gastritis samples).

CONCLUSIONS

Given our evidence about the possibility of involvement of NHPGHs in patients suffering from gastritis and nonexistence of mixed H. pylori infection, bacteriological testing of subjects negative for H. pylori becomes clinically relevant and important. Our findings suggest H. salomonis has the highest rate among the NHPGH species in Iranian dyspeptic patients.

Association Between Acid-Suppressive Agents’ Use and Risk of Hepatocellular Carcinoma

Background:

Acid-suppressive agents (ASAs), which are mostly used in patients with upper gastrointestinal diseases (UGIDs), may influence the risk of hepatocellular carcinoma (HCC).

Methods:

A population-based retrospective cohort study was conducted. Patients with UGID who used ASAs and those who did not receive ASAs were identified. Patients without UGIDs were randomly selected and matched (comparison group). All groups were followed up for 6 years. A Cox proportional hazard model was used to estimate the risk of HCC among the different groups.

Results:

Patients with UGID who used ASAs had a significantly elevated HCC risk (adjusted hazard ratio [HR] 1.53; 95% confidence interval [CI], 1.32-1.76] compared to those who did not use ASAs. Patients with UGID who used more than 540 defined daily doses of ASAs had a significantly higher risk of HCC (adjusted HR 2.04; 95% CI, 1.62-2.58). Moreover, the dose effect on HCC risk exhibited a significant increasing trend ( P < .01). Furthermore, patients with UGID who did not use ASAs had a significantly elevated HCC risk (adjusted HR 1.94; 95% CI, 1.59-2.36) compared to the comparison group.

Conclusion:

The use of ASAs increased the risk of HCC in patients with UGIDs, and the effect of ASAs was dose dependent. In addition, UGIDs alone increased the risk of HCC.

Systematic review: the effects of proton pump inhibitors on the microbiome of the digestive tract-evidence from next-generation sequencing studies

BACKGROUND

Proton pump inhibitors (PPI) are widely used to treat acid-related disorders of the upper gastrointestinal tract. However, large observational studies have raised concerns about PPI-associated adverse events. In recent years, data from next-generation sequencing studies suggested that PPIs affect the composition of the intestinal microbiota, while a balanced gut microbiome is essential for maintaining health.

AIM

To review the available evidence from next-generation sequencing studies on the effect of PPIs on the intestinal microbiome and to discuss possible implications of PPI-induced dysbiosis in health and disease.

METHODS

A systematic review was conducted following the recommendations of the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement. A PubMed query yielded 197 results. 19 publications met the prespecified eligibility criteria.

RESULTS

Twelve observational study cohorts with 708 PPI users and 11 interventional cohorts with 180 PPI users were included in the review. In most studies, PPI treatment did not affect microbiological richness and diversity, but was associated with distinct taxonomic alterations: In the upper gastrointestinal tract, PPI users showed overgrowth of orally derived bacteria, mostly Streptococcaceae (findings based on six independent cohorts with 126 PPI users). In faecal samples, PPIs increased multiple taxa from the orders Bacillales (eg, Staphylococcaceae), Lactobacillales (eg, Enterococcaceae, Lactobacillaceae, Streptococcaceae) and Actinomycetales (eg, Actinomycetaceae, Micrococcaceae), the families Pasteurellaceae and Enterobacteriaceae and the genus Veillonella. Taxa decreased by PPIs include Bifidobacteriaceae, Ruminococcaceae, Lachnospiraceae and Mollicutes (findings in faecal samples based on 19 independent cohorts with 790 PPI users).

CONCLUSION

PPI use is associated with moderate alterations to upper and distal gut microbiota. The available data suggest that PPI-induced hypochlorhydria facilitates colonization of more distal parts of the digestive tract by upper gastrointestinal microbiota.

The role of the gastric bacterial microbiome in gastric cancer: Helicobacter pylori and beyond

A link between chronic inflammation and carcinogenesis has been depicted in many organ systems. Helicobacter pylori is the most prevalent bacterial pathogen, induces chronic gastritis and is associated with more than 90% of cases of gastric cancer (GC). However, the introduction of nucleotide sequencing techniques and the development of biocomputional tools have surpassed traditional culturing techniques and opened a wide field for studying the mucosal and luminal composition of the bacterial gastric microbiota beyond H. pylori. In studies applying animal models, a potential role in gastric carcinogenesis for additional bacteria besides H. pylori has been demonstrated. At different steps of gastric carcinogenesis, changes in bacterial communities occur. Whether these microbial changes are a driver of malignant disease or a consequence of the histologic progression along the precancerous cascade, is not clear at present. It is hypothesized that atrophy, as a consequence of chronic gastric inflammation, alters the gastric niche for commensals that might further urge the development of H. pylori-induced GC. Here, we review the current state of knowledge on gastric bacteria other than H. pylori and on their synergism with H. pylori in gastric carcinogenesis.

The Clinician's Guide to Proton Pump Inhibitor Related Adverse Events

A substantial volume of literature exists linking proton pump inhibitor (PPI) use with a multitude of serious adverse events. There is uncertainty, however, over whether these associations are clinically important. Excessive concern about PPI-related adverse events may leave patients at risk of harm by leaving acid-related upper gastrointestinal disease untreated. Conversely, the risk of treatments may outweigh the benefits if any of the purported adverse events are directly caused by PPI use; this is of particular concern where indications for PPI use are not present. In this paper, we review the studies which have reported associations between adverse events and PPI use, discuss the proposed mechanisms of action, grade the confidence in whether these associations are truly causal, and provide advice regarding balancing the benefits of PPI use against their possible harms.

What is the Relevance of Gastric Microbiota Beyond H. pylori?

PURPOSE

The role of Helicobacter pylori as key factor in gastric inflammation and the development of (pre-)cancerous lesions is undisputable. As an open system, the human upper gastrointestinal tract harbors a complex bacterial community which is highly impacted by the absence or presence of H. pylori. The interaction between other bacteria and H. pylori might impact on gastric carcinogenesis.

RECENT FINDINGS

Several studies demonstrated differences in the composition of the gastric bacterial community in different stages of gastritis and between samples from tumor and adjacent tissue. In addition, animal studies demonstrated an increased and accelerated development of precancerous lesions in mice colonized with intestinal flora and H. pylori compared with mice mono-infected with H. pylori.

CONCLUSION

Other bacteria beyond H. pylori enter the focus in research on gastric carcinogenesis. However, we are still far from a thorough understanding of the pathophysiology of host-microbiota interaction and its impact on the development of malignant and precancerous changes.

Relationship between long-term use of proton pump inhibitors and risk of gastric cancer: A systematic analysis

BACKGROUND AND AIM

This study aims to systematically analyze the effect of long-term therapy with proton pump inhibitors (PPIs) on the risk of gastric cancer.

METHODS

PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI), and China biomedical literature database (CBM) were searched for studies before February 2019. We evaluated the quality of the included articles through the Newcastle-Ottawa Scale and gathered relevant data to calculate the pooled odds ratio (OR) through Stata14.0.

RESULTS

Seven relevant articles conformed to the inclusion criteria; 943 070 patients were included. The pooled OR was 2.50; 95% CI (1.74, 3.85); the subgroup analysis results showed that patients who had used PPIs for more than 36 months were most likely to develop gastric cancer, and an increased risk was observed among patients after Helicobacter pylori eradication. Noncardia gastric cancer was more likely to develop.

CONCLUSIONS

Long-term use of PPIs can possibly increase the risk of gastric cancer even among patients after H. pylori eradication; in particular, for noncardia gastric cancer, the risk increases with longer durations of PPI use. Due to the limited number of studies, more high-quality studies are required to be designed.

Bacterial colonization of the stomach and duodenum in a Swedish population with and without proton pump inhibitor treatment

Background and Aim

Microbial contamination of the abdominal cavity is a serious concern during transgastric endoscopic interventions and perforations, particularly in patients who have inhibited gastric acid secretion due to treatment with proton pump inhibitors (PPIs).

The aim of this study was to investigate the gastric and duodenal bacterial flora in patients with and without PPI treatment.

Methods

Patients referred for gastroscopy, without recent antibiotic treatment, were eligible for inclusion. Use of PPIs was recorded. Samples for bacterial culturing were obtained from the antrum of the stomach and from the duodenal bulb through a gastroscope. Positive cultures were examined for bacterial types and subtypes. Biopsies were taken in the antrum for urease test to detect Helicobacter pylori.

Results

Bacterial cultures from the stomach were obtained from 103 patients, and duodenal samples were also cultured from 49 of them, for a total of 53 patients with PPI use and 50 patients without. Positive gastric cultures were found in 42 of 53 patients with PPI use and in 13 of 50 without (P < 0.0001). Duodenal cultures were positive in 20 of 24 with PPI and 8 of 25 without (P < 0.0001). The most commonly identified bacterial species were oral strains of Streptococcus, followed by Neisseria and Haemophilus influenzae. Of 103 patients, 10 had a positive urease test, indicating H. pylori infection, 1 with PPI and 9 without.

Conclusions

Bacterial growth in the stomach and duodenum is more common in patients with PPI treatment. The dominating bacterial species found in the stomach and duodenum originates from the oropharynx.

Clinical trials registry: Trial registration number 98041 in Researchweb (FoU in Sweden).

Impact of the Gastrointestinal Microbiome in Health and Disease: Co-evolution with the Host Immune System

Microbes within the gastrointestinal tract communicate with each other and with the host, which has profound effects on health and disease development. Only now, it is becoming apparent that how and when we acquire our own unique collection of "gut microbes" and also how we choose to maintain them is fundamental to our health. Helicobacter pylori is the most common bacterial infection worldwide, colonizing around half of the world's population, and is the major risk factor for gastric adenocarcinoma. More recently, it has also been shown to have some beneficial effects in terms of protecting against the development of other diseases. Here, we review the current knowledge on how H. pylori has shaped gastrointestinal microbiota colonization and the host immune system with specific focus on the impact of H. pylori on the various microbiome niches of the gastrointestinal tract. We discuss how the presence of H. pylori influences the physiology of three major regions within the gastrointestinal tract-specifically the oesophagus, stomach and colon. We pay particular attention to the role of H. pylori under chronic inflammatory conditions including the development of cancer. With increased incidence of diseases such as eosinophilic oesophagitis, oesophageal adenocarcinoma and squamous cell carcinoma being attributed to the decline in H. pylori, their disease pathogenesis in light of changing H. pylori colonization is also discussed.

A Novel View of Human Helicobacter pylori Infections: Interplay between Microbiota and Beta-Defensins

The gut microbiota is significantly involved in the preservation of the immune system of the host, protecting it against the pathogenic bacteria of the stomach. The correlation between gut microbiota and the host response supports human gastric homeostasis. Gut microbes may be shifted in Helicobacter pylori (Hp)-infected individuals to advance gastric inflammation and distinguished diseases. Particularly interesting is the establishment of cooperation between gut microbiota and antimicrobial peptides (AMPs) of the host in the gastrointestinal tract. AMPs have great importance in the innate immune reactions to Hp and participate in conservative co-evolution with an intricate microbiome. β-Defensins, a class of short, cationic, arginine-rich proteins belonging to the AMP group, are produced by epithelial and immunological cells. Their expression is enhanced during Hp infection. In this review, we discuss the impact of the gut microbiome on the host response, with particular regard to β-defensins in Hp-associated infections. In microbial infections, mostly in precancerous lesions induced by Hp infection, these modifications could lead to different outcomes.

Gastric Parietal Cell Physiology and Helicobacter pylori-Induced Disease

Acidification of the gastric lumen poses a barrier to transit of potentially pathogenic bacteria and enables activation of pepsin to complement nutrient proteolysis initiated by salivary proteases. Histamine-induced activation of the PKA signaling pathway in gastric corpus parietal cells causes insertion of proton pumps into their apical plasma membranes. Parietal cell secretion and homeostasis are regulated by signaling pathways that control cytoskeletal changes required for apical membrane remodeling and organelle and proton pump activities. Helicobacter pylori colonization of human gastric mucosa affects gastric epithelial cell plasticity and homeostasis, promoting epithelial progression to neoplasia. By intervening in proton pump expression, H pylori regulates the abundance and diversity of microbiota that populate the intestinal lumen. We review stimulation-secretion coupling and renewal mechanisms in parietal cells and the mechanisms by which H pylori toxins and effectors alter cell secretory pathways (constitutive and regulated) and organelles to establish and maintain their inter- and intracellular niches. Studies of bacterial toxins and their effector proteins have provided insights into parietal cell physiology and the mechanisms by which pathogens gain control of cell activities, increasing our understanding of gastrointestinal physiology, microbial infectious disease, and immunology.

Potential Role of Biofilm Formation in the Development of Digestive Tract Cancer With Special Reference to Helicobacter pylori Infection

Bacteria are highly social organisms that communicate via signaling molecules and can assume a multicellular lifestyle to build biofilm communities. Until recently, complications from biofilm-associated infection have been primarily ascribed to increased bacterial resistance to antibiotics and host immune evasion, leading to persistent infection. In this theory and hypothesis article we present a relatively new argument that biofilm formation has potential etiological role in the development of digestive tract cancer. First, we summarize recent new findings suggesting the potential link between bacterial biofilm and various types of cancer to build the foundation of our hypothesis. To date, evidence has been particularly convincing for colorectal cancer and its precursor, i.e., polyps, pointing to several key individual bacterial species, such as Bacteroides fragilis, Fusobacterium nucleatum, and Streptococcus gallolyticus subsp. Gallolyticus. Then, we further extend this hypothesis to one of the most common bacterial infection in humans, Helicobacter pylori (Hp), which is considered a major cause of gastric cancer. Thus far, there has been no direct evidence linking in vivo Hp gastric biofilm formation to gastric carcinogenesis. Yet, we synthesize the information to support an argument that biofilm associated-Hp is potentially more carcinogenic, summarizing biological characteristics of biofilm-associated bacteria. We also discuss mechanistic pathways as to how Hp or other biofilm-associated bacteria control biofilm formation and highlight recent findings on Hp genes that influence biofilm formation, which may lead to strain variability in biofilm formation. This knowledge may open a possibility of developing targeted intervention. We conclude, however, that this field is still in its infancy. To test the hypothesis rigorously and to link it ultimately to gastric pathologies (e.g., premalignant lesions and cancer), studies are needed to learn more about Hp biofilms, such as compositions and biological properties of extracellular polymeric substance (EPS), presence of non-Hp microbiome and geographical distribution of biofilms in relation to gastric gland types and structures. Identification of specific Hp strains with enhanced biofilm formation would be helpful not only for screening patients at high risk for sequelae from Hp infection, but also for development of new antibiotics to avoid resistance, regardless of its association with gastric cancer.