A Cohort Study of the Influence of the 12-Component Modified Japanese Diet Index on Oral and Gut Microbiota in the Japanese General Population.

The Japanese diet is a healthy dietary pattern, and the oral or gut microbiota have been identified as the main factors underlying the beneficial effects of the Japanese diet. However, epidemiological studies on Japanese dietary patterns calculated from daily eating habits in the general population yielded inconsistent findings. This study aimed to determine the association between the 12-component modified Japanese Diet Index (mJDI12) and the oral and gut microbiota in the general population of a rural area in Japan. After propensity-score matching, 396 participants (198 each in the low and high mJDI12 groups) were picked out. One year after the follow up survey, we reclassified the subjects and compared the low and high mJDI12 groups again. Participants with a high mJDI12 had a higher relative abundance of butyric acid-producing bacteria in their gut microbiota. Moreover, the significantly higher dietary fiber intake in the high mJDI12 group suggested that the high intake of dietary fiber contributed to an increase in butyric acid-producing bacteria in the gut. In contrast, in individuals with a high mJDI12, only Allpprevotella was decreased in the oral microbiota. Thus, the Japanese dietary pattern can have beneficial effects by improving the oral and gut microbiota.

Antimicrobial-resistant Helicobacter pylori in Japan: Report of nationwide surveillance for 2018-2020.

BACKGROUND: Antimicrobial therapy is necessary to eradicate Helicobacter pylori infection. The emergence of antimicrobial-resistant bacteria poses a threat to continued treatment with antimicrobial agents. For those who prescribe antimicrobial therapy, it is necessary to constantly monitor the emergence of antimicrobial-resistant bacteria. METHOD: H. pylori clinical isolates were collected in Japan from August 2018 to December 2020 for antimicrobial susceptibility testing. The agar dilution method was used for the determination of the minimum inhibitory concentration (MIC) of clarithromycin (CLR), amoxicillin (AMX), metronidazole (MNZ), and sitafloxacin (STX). RESULTS: MICs for 938 H. pylori isolates were examined. The primary resistance rates of H. pylori clinical isolates for CLR, AMX, MNZ, and STX in Japan were 35.5%, 2.7%, 4.2%, and 27.6%, respectively. The primary resistance rates for CLR, AMX, and MNZ were significantly higher than those of the 2002-2005 isolates. The resistance rate for CLR was significantly higher in females (males: 30.7%, females: 41.5%, p < 0.001) and higher in the ≤29 years age group (54.8%) than in the other age groups, although there were no significant differences (p = 0.104). The MNZ resistance rate was significantly higher in the ≤29 years age group than in the other age groups (p = 0.004). The resistance rate for STX increased with age, but a significant difference was only seen between the 30-49 years age group and the ≥70 years age group (p < 0.001), and the resistance rate was significantly higher in strains isolated in the Kyushu region than in the other regions (p < 0.001). CONCLUSIONS: The primary resistance rates for CLR, AMX, and MNZ of H. pylori clinical isolates in Japan were higher than those of the 2002-2005 isolates. Continuous surveillance is needed to monitor the trends in antimicrobial-resistant H. pylori.

A Logistic Regression Model for Predicting the Risk of Subsequent Surgery among Patients with Newly Diagnosed Crohn's Disease Using a Brute Force Method.

Surgery avoidance is an important goal in Crohn's disease (CD) treatment and predicting the risk of subsequent surgery is important to determine adequate therapeutic strength for patients with newly diagnosed CD. Herein, we aimed to construct a prediction model for the risk of subsequent surgery based on disease characteristics at the patients' initial visit. We retrospectively collected disease characteristic data from 93 patients with newly diagnosed CD. A logistic regression model with a brute force method was used to maximize the area under the receiver operating characteristic curve (auROC) by employing a combination of potential predictors from 14 covariates (16,383). The auROC remained almost constant when one to 12 covariates were considered, reaching a peak of 0.89 at four covariates (small-bowel patency, extensive small-bowel lesions, main lesions, and the number of poor prognostic factors), and it decreased with increasing covariate size. The most significant predictors were small-bowel patency, extensive small-bowel lesions, and age or major lesions. Therefore, this prediction model using covariates may be helpful in determining the likelihood that a patient with newly diagnosed CD will require surgery, which can aid in appropriate treatment selection for high-risk patients.

Association between reactive oxygen species production in neutrophils and liver fibrosis in the general population.

Fibrosis, induced by reactive oxygen species (ROS) production in neutrophils, has harmful effects on the liver and various other organs. However, little is known about the association between liver fibrosis and ROS levels in neutrophils in the general population. This large-scale epidemiological study aimed to determine the association between liver fibrosis and neutrophil-generated ROS levels according to age and sex in the general population. This cross-sectional study included 1,000 participants from a district health promotion project. Participants were grouped based on sex (male; female) and age (young, <65 years; old, ≥65 years). The four groups were as follows: male, young (n = 289); male, old (n = 100); female, young (n = 425); and female, old (n = 186). Liver fibrosis was assessed using the fibrosis 4 (FIB-4) index, aspartate aminotransferase-to-platelet ratio index (APRI), and non-alcoholic fatty liver disease (NAFLD) fibrosis score (NFS). Basal and stimulated ROS were considered in the analysis. Multiple linear analyses showed (1) significant positive correlations between all liver fibrosis scores and basal ROS in the young groups, and (2) significant negative correlations between NFS and stimulated ROS in females. Preventing liver fibrosis through neutrophil-related immune system enhancement may avert the development of lifestyle-related diseases and infections.

Effect of Liver Fibrosis on Oral and Gut Microbiota in the Japanese General Population Determined by Evaluating the FibroScan-Aspartate Aminotransferase Score.

The association between liver fibrosis and oral or gut microbiota has been studied before. However, epidemiological studies in the general population are limited owing to the difficulty of noninvasive liver-fibrosis assessment. FibroScan-asparate aminotransferase (FAST) scores can be used to accurately and non-invasively evaluate liver fibrosis. This study aimed to determine the association between liver fibrosis and oral or gut microbiota using the FAST score in the general population. After propensity score matching of 1059 participants based on sex, age, body mass index, homeostasis model assessment of insulin resistance, and triglyceride levels, 125 (non-liver-fibrosis group, 100; liver fibrosis group, 25) were included. The diversity of gut microbiota differed significantly between the two groups; however, no significant differences were noted in their oral microbiota. The liver fibrosis group showed an increase in the relative abundance of Fusobacteria strains and a decrease in the relative abundance of Faecalibacterium, with the presence of Fusicatenibacter in the gut microbiota. Feacalibacterium was not identified as an independent factor of liver fibrosis in adjusting the fatty liver index. In the general population, gut microbiota may be more involved in liver fibrosis than oral microbiota.

Assessment of the Physical Invasiveness of Peroral Endoscopic Myotomy during the Perioperative Period Based on Changes in Energy Metabolism.

A novel treatment method for achalasia of the esophagus and related disorders is known as peroral endoscopic myotomy (POEM). This study aimed to calculate the resting energy expenditure (REE) and evaluated the degree of physical invasiveness based on metabolic changes during the perioperative period of POEM. Fifty-eight patients who underwent POEM were prospectively enrolled; REE, body weight (BW), and basal energy expenditure were measured on the day of POEM, postoperative day 1 (POD 1), and three days after POEM (POD 3). The median REE/BW increased from 19.6 kcal/kg on the day of POEM to 24.5 kcal/kg on POD 1. On POD 3, it remained elevated at 20.9 kcal/kg. The stress factor on POD 1 was 1.20. Among the factors, including the Eckardt score, operation time, and the length of myotomy, the length of myotomy was associated with changes in REE/BW. During the perioperative period of POEM, the level of variation in energy expenditure was lower than that of esophageal cancer surgeries performed under general anesthesia. However, because the length of myotomy is a factor affecting changes in energy expenditure, careful perioperative management is desirable for patients with longer myotomy lengths.

Vitamin A Promotes the Fusion of Autophagolysosomes and Prevents Excessive Inflammasome Activation in Dextran Sulfate Sodium-Induced Colitis.

Vitamin A ensures intestinal homeostasis, impacting acquired immunity and epithelial barrier function; however, its role in innate immunity is mostly unknown. Here, we studied the impact of vitamin A in different dextran sulfate sodium (DSS)-induced colitis animal models. Interestingly, more severe DSS-induced colitis was observed in vitamin A-deficient (VAD) mice than in vitamin A-sufficient (VAS) mice; the same was observed in VAD severe combined immunodeficient mice lacking T/B cells. Remarkably, IL-1ß production, LC3B-II expression, and inflammasome activity in the lamina propria were significantly elevated in VAD mice. Electron microscopy revealed numerous swollen mitochondria with severely disrupted cristae. In vitro, non-canonical inflammasome signaling-induced pyroptosis, LC3B-II and p62 expression, and mitochondrial superoxide levels were increased in murine macrophages (RAW 264.7) pretreated with retinoic acid receptor antagonist (Ro41-5253). These findings suggest that vitamin A plays a crucial role in the efficient fusion of autophagosomes with lysosomes in colitis.

Evaluation of Crohn's Disease Small-Bowel Mucosal Healing Using Capsule Endoscopy and Usefulness of Leucine-Rich α2-Glycoprotein.

Recently, the importance of achieving clinical and deep remissions with mucosal healing (MH) has been demonstrated as a therapeutic goal to avoid Crohn's disease (CD) surgical operations. Although ileocolonoscopy (CS) is considered the gold standard, there are increasing reports on the benefits of capsule endoscopy (CE) and serum leucine-rich α2-glycoprotein (LRG) for evaluating small-bowel lesions in CD. We evaluated the data of 20 patients with CD who underwent CE in our department between July 2020 and June 2021 and whose serum LRG level was measured within 2 months. Concerning the mean LRG value, there was no significant difference between the CS-MH and CS-non-MH groups. Conversely, the mean LRG level was 10.0 µg/mL in seven patients in the CE-MH group and 15.2 µg/mL in 11 patients in the CE-non-MH group with a significant difference between the two groups (p = 0.0025). This study's findings show that CE can sufficiently determine total MH in most cases, and LRG is useful for evaluating CD small-bowel MH because of its correlation with CE-MH. Furthermore, satisfying CS-MH criteria and a cut-off value of 13.4 µg/mL for LRG suggests its usefulness as a CD small-bowel MH marker, which could be incorporated into the treat-to-target strategy.

Bacterial exposure risk to the endoscopist's face while performing endoscopy.

Objectives: Gastrointestinal endoscopy increases the risk of bacterial exposure to endoscopists. However, before 2019, most endoscopists did not pay attention to microorganism transmission from patients. This study aimed to investigate the incidence of bacterial exposure to endoscopists' faces during gastrointestinal endoscopic procedures using the bacterial culture method. Methods: This was a single-centered, retrospective study including endoscopists who performed various gastrointestinal endoscopy procedures at the Division of Endoscopy, Hirosaki University Hospital between August 31 and October 6, 2020. Endoscopists wore surgical masks and affixed pre-sterilized films over them. Following the gastrointestinal endoscopic procedures, attached microbes were collected from the endoscopists' surface films using sterilized swabs. Collected microorganisms were cultured on tryptic soy agar and 5% sheep blood agar, and the incidence of bacterial exposure was determined by bacterial culture positivity. Cultured bacteria were identified by gram staining and 16S rRNA gene sequencing. Results: Bacterial culture positivity was 12.6%, and it was significantly higher in therapeutic than in diagnostic endoscopy. Notably, therapeutic endoscopy increased bacterial culture positivity in colonoscopy, but not in esophagogastroduodenoscopy. Staphylococci, including Staphylococcus epidermidis and Staphylococcus capitis, were the most commonly found bacteria in samples identified through 16S rRNA gene sequencing. Conclusions: The risk of bacterial exposure to the endoscopist's face was increased in colonoscopy treatment procedures. Therefore, endoscopists should be aware of the significant risk of microbial infection from scattering fluid that comes from the endoscopy's working channel.

Assessment of physical stress during the perioperative period of endoscopic submucosal dissection.

The advantage of endoscopic submucosal dissection (ESD) is that it is less invasive than surgery. ESD is one of the best treatments for older patients as surgery in this age group of patients is difficult. However, it is unclear how much lower the physical stress of ESD is compared with that of surgery. Thus, objective methods are required to assess physical stress in patients who have undergone ESD. The current review of ESD aimed to summarize the recent advancements in the assessment of physical stress during the perioperative period, focusing on changes in energy metabolism and serum opsonic activity (SOA). Based on metabolic changes, resting energy expenditure (REE) was measured using an indirect calorimeter. The stress factor calculated from the REE and the basal energy expenditure computed using the Harris-Benedict equation can be used to assess physical stress. SOA was assessed using the chemiluminescence method, wherein the use of chemiluminescent probes (i.e., lucigenin and luminol) allowed quantification of reactive oxygen species generated by neutrophils. Using an auto luminescence analyzer, the results were evaluated based on the maximum light emission and area under the emission curve. These quantifiable results revealed the minimal invasiveness of ESD.

A Cohort Study of the Effects of Daily-Diet Water-Soluble Dietary Fiber on Butyric Acid-Producing Gut Microbiota in Middle-Aged and Older Adults in a Rural Region.

Water-soluble dietary fiber is primarily a substrate for degradation of short chain fatty acids (SCFAs), particularly butyric acid, by gut microbiota. SCFAs have beneficial effects on the whole body. However, epidemiological studies on the association between water-soluble dietary fiber from daily food intake and butyric acid-producing bacteria are inconsistent. The purpose of this study was to determine the association between levels of water-soluble dietary fiber from daily food intake and gut microbiota, particularly butyric acid producers, in middle-aged and older adults in a rural area in Japan. We examined the effects of water-soluble dietary fiber intake on gut microbiota after adjusting for confounding factors. After propensity score matching, 520 subjects (260 in the low-intake group and 260 in the high-intake group) were selected. One year later after a follow-up survey, we re-classified the participants and again compared low- and high-intake groups. As a result, people with a high intake had a higher relative abundance of butyric acid-producing bacteria. It was also revealed that butyric acid-producing bacteria remained high in the group that maintained high intake the next year. We concluded that continuous intake of water-soluble dietary fiber from daily food is necessary to maintain sufficient amounts of butyric acid-producing bacteria.

Automated evaluation of colon capsule endoscopic severity of ulcerative colitis using ResNet50.

Capsule endoscopy has been widely used as a non-invasive diagnostic tool for small or large intestinal lesions. In recent years, automated lesion detection systems using machine learning have been devised. This study aimed to develop an automated system for capsule endoscopic severity in patients with ulcerative colitis along the entire length of the colon using ResNet50. Capsule endoscopy videos from patients with ulcerative colitis were collected prospectively. Each single examination video file was partitioned into four segments: the cecum and ascending colon, transverse colon, descending and sigmoid colon, and rectum. Fifty still pictures (576 × 576 pixels) were extracted from each partitioned video. A patch (128 × 128 pixels) was trimmed from the still picture at every 32-pixel-strides. A total of 739,021 patch images were manually classified into six categories: 0) Mayo endoscopic subscore (MES) 0, 1) MES1, 2) MES2, 3) MES3, 4) inadequate quality for evaluation, and 5) ileal mucosa. ResNet50, a deep learning framework, was trained using 483,644 datasets and validated using 255,377 independent datasets. In total, 31 capsule endoscopy videos from 22 patients were collected. The accuracy rates of the training and validation datasets were 0.992 and 0.973, respectively. An automated evaluation system for the capsule endoscopic severity of ulcerative colitis was developed. This could be a useful tool for assessing topographic disease activity, thus decreasing the burden of image interpretation on endoscopists.

Influence of Esophageal Endoscopic Submucosal Dissection on the Changes of Energy Metabolism during the Perioperative Period.

Esophageal endoscopic submucosal dissection (ESD) is considered to be more complex than gastric ESD. This study aimed to assess the physical invasiveness of esophageal ESD during perioperative periods by measuring resting energy expenditure (REE). The factors affecting REE that could be used to identify patients requiring perioperative management were also investigated. Overall, 75 patients who had undergone esophageal ESD were prospectively enrolled. REE, body weight, and basal energy expenditure were measured on the day of and the day following ESD. The mean REE/body weight was 20.2 kcal/kg/day on the day of ESD and significantly increased to 23.0 kcal/kg/day one day after ESD. The stress factor on the day after ESD was 1.11. White blood cell, neutrophil, and C-reactive protein levels increased on the day after ESD and correlated with the changes in REE. Among the factors including age, body mass index, total resection area, operation time, and sarcopenia, only the total resection area was associated with changes in REE. In conclusion, energy metabolism increases during the perioperative period for esophageal ESD. The increase in the stress factor for esophageal ESD was higher than that in gastric and colorectal ESD. Furthermore, patients with large resection areas require greater attention in perioperative management.

Spatial distribution of live gut microbiota and bile acid metabolism in various parts of human large intestine.

Gut microbiomics is based on analysis of both live and dead cells in the stool. However, to understand the ecology of gut microbiota and their symbiotic relationships with hosts, spatial distribution of live bacteria must be examined. Here, we analyzed the live composition of luminal microbiota (LM) and mucosa-associated microbiota (MAM) in the ascending and descending colons and the rectums of 10 healthy adults and compared it with the total composition. The abundance of Lachnospiraceae in live LM decreased along the gut length and was significantly lower than that in total LM. Contrastingly, the abundance of Bacteroidaceae and Bifidobacteriaceae in live LM was higher than that in total LM, suggesting differences in death rate during gut migration. Live Enterobacteriaceae levels in MAM were significantly higher in rectum than in the ascending and descending colons and in LM. High-performance liquid chromatographic analysis of luminal bile acids revealed that 7α-dehydroxylation occurred towards the rectum. In live LM where a bile acid-inducible gene could be detected, 7α-dehydroxylation rates were higher than those in the group without the gene. Overall, we showed differences in live bacteria composition among three gut sites and between LM and MAM, highlighting the importance of understanding their spatial distribution.

Endoscopic and histopathologic features of Anti-PD-1-related collagenous colitis.

Objectives: Cancer patients treated with immune checkpoint inhibitors occasionally show persistent diarrhea accompanied by endoscopic features of ulcerative colitis. The endoscopic mucosal inflammation may appear mild in some patients compared to the clinical severity, which can make choosing a treatment challenging. In this study, we evaluated the factors that support the continuation of chemotherapy by assessing the endoscopic and histopathological characteristics of patients who experienced diarrhea after immune checkpoint inhibitor administration. Methods: This study included eight patients who were diagnosed with collagenous colitis based on pathological assessments. We retrospectively investigated these patients' backgrounds, laboratory data, and computed tomography images that were extracted from their medical records. We also summarized their endoscopic and pathologic findings. Results: All eight patients were being treated with anti-programmed cell death-1/programmed cell death-ligand 1 therapeutic agents and had a recent history of oral proton pump inhibitor therapy. The anti-programmed cell death-1-related collagenous colitis in these cases was characterized by endoscopically mild mucosal inflammation, high fecal calprotectin levels, and a lower frequency of intestinal wall thickening on computed tomography. Histological assessments showed CD8+ lymphocytes predominantly infiltrating the lamina propria and crypts of the colonic mucosa. Suspending the proton pump inhibitor therapy relieved the patients' symptoms and allowed the continuation of the anti-programmed cell death-1/programmed cell death-ligand 1 therapy. Conclusions: Anti-programmed cell death-1-related collagenous colitis is reversible; appropriate diagnosis of adverse events is crucial for the continuation of immune checkpoint inhibitor therapy.

Long-term efficacy and tolerability of dose-adjusted thiopurine treatment in maintaining remission in inflammatory bowel disease patients with NUDT15 heterozygosity.

BACKGROUND/AIMS: Thiopurines are key drugs for inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD). Recently, NUDT15 polymorphism (R139C, c.415C > T) has been shown to be associated with thiopurineinduced adverse events in Asian populations. In patients with the C/T genotype, low-dose thiopurine treatment is recommended, but its long-term efficacy and tolerability remain unclear. This study aimed to uncover the long-term efficacy and appropriate dosage of thiopurine for IBD patients with the C/T genotype. METHODS: A total of 210 patients with IBD (103 UC and 107 CD) determined to have NUDT15 R139C variants were enrolled. Clinical data were retrospectively reviewed from medical records. RESULTS: Of 46 patients (21.9%) with the C/T genotype, 30 patients (65.2%) were treated with thiopurines. Three of whom (10.0%) discontinued thiopurine treatment due to adverse events and 27 of whom continued. The median maintenance dosage of 6-mercaptopurine was 0.25 mg/kg/day (range, 0.19-0.36 mg/kg/day), and 6-thioguanine nucleotides level was 230 (104-298) pmol/8 × 108 red blood cells. Cumulative thiopurine continuation rates for 120 months for patients with the C/C and C/T genotypes were not significantly different (P= 0.895). Cumulative non-relapse rates in the patients with UC treated with thiopurine monotherapy and surgery-free rates in CD patients treated with combination therapy (thiopurines and anti-tumor necrosis factor-α agents) for maintenance remission were not significantly different at 60 months (C/C vs. C/T, P= 0.339 and P= 0.422, respectively). CONCLUSIONS: Low-dose thiopurine treatment is an effective and acceptable treatment for patients with C/T genotype.

Esophageal achalasia with mucosal damage due to enteric-coated aspirin.

A 76-year-old man was referred to our hospital for examination and treatment of dysphagia. He has been taking enteric-coated aspirin for myocardial infarction. Esophagogastroduodenoscopy (EGD) revealed the presence of esophageal ulcers in the distal esophagus and five to six tablets of enteric-coated aspirin. The esophageal ulcers were believed to have been caused by the retention of aspirin within the esophagus due to achalasia. We substituted enteric-coated aspirin with powdered aspirin. A follow-up EGD performed 1 month later showed improvement of esophageal mucosa. The patient was diagnosed with type I achalasia. Per-oral endoscopic myotomy was performed, and his symptoms improved after the procedure. Although a few studies have investigated the direct effect of aspirin, none of them has reported on the direct effect of aspirin on the esophagus. It might be effective to administer powdered aspirin for patients with achalasia to prevent esophageal ulcers caused by the direct effect of aspirin.

Effective Endoscopic Closure of Cholecysto-duodenal and Transverse Colon Fistulas Due to Squamous Cell Carcinoma of the Gallbladder Using Polyglycolic Acid Sheets and a Covered Metal Stent.

An 81-year-old woman presented with abdominal distension and right hypochondrial pain. Abdominal contrast computed tomography and magnetic resonance imaging revealed an 11-cm gallbladder tumor. The patient was diagnosed with squamous cell carcinoma of the gallbladder by endoscopic ultrasound-guided fine-needle aspiration from the gastric antrum. Thereafter, the gallbladder tumor enlarged, and cholecysto-duodenal and transverse colon fistulas were formed. A covered metal stent was placed on the transverse colon, and polyglycolic acid sheets were injected into the duodenum to close the fistulas endoscopically. Endoscopic closure is less invasive than surgery and considered effective for patients with poor general health conditions.

Dynamic analysis of human small intestinal microbiota after an ingestion of fermented milk by small-intestinal fluid perfusion using an endoscopic retrograde bowel insertion technique.

Probiotic products have been shown to have beneficial effects on human hosts, but what happens in the gastrointestinal tract after its ingestion remains unclear. Our aim was to investigate the changes within the small intestines after a single intake of a fermented milk product containing a probiotic. We have periodically collected the small-intestinal fluids from the terminal ileum of seven healthy subjects for up to 7 h after ingestion by small-intestinal fluid perfusion using an endoscopic retrograde bowel insertion technique. The bacterial composition of the terminal ileum clearly revealed that the ingested probiotics (Lactobacillus casei strain Shirota: LcS and Bifidobacterium breve strain Yakult: BbrY) occupied the ileal microbiota for several hours, temporarily representing over 90% of the ileal microbiota in several subjects. Cultivation of ileal fluids showed that under a dramatic pH changes before reaching the terminal ileum, a certain number of the ingested bacteria survived (8.2 ± 6.4% of LcS, 7.8 ± 11.0% of BbrY). This means that more than 1 billion LcS and BbrY cells reached the terminal ileum with their colony-forming ability intact. These results indicate that there is adequate opportunity for the ingested probiotics to continuously stimulate the host cells in the small intestines. Our data suggest that probiotic fermented milk intake affects intestinal microbes and the host, explaining part of the process from the intake of probiotics to the exertion of their beneficial effects on the host.

Influence of Helicobacter pylori Infection and Atrophic Gastritis on the Gut Microbiota in a Japanese Population.

BACKGROUND: Although infection with Helicobacter pylori and subsequent atrophic gastritis modulate the gastric conditions, their relationship with the gut microbiota in -Japanese population has not been clearly characterized. METHODS: A cohort of 1,123 subjects who participated in a health survey was studied. Infection of H. pylori was defined by both serum antibody and stool antigen test. The presence and severity of atrophic gastritis were defined by serum levels of pepsinogens. The relative abundance of each bacterial species in fecal samples was calculated by using 16S ribosomal RNA amplification, and the composition ratios of bacterial taxa were evaluated using propensity score matching. RESULTS: The abundance of 3 orders, 4 families, and 4 genera was significantly higher in H. pylori-infected subjects than in noninfected subjects (false discovery rate [FDR] <0.05). In H. pylori-infected subjects with severe atrophic gastritis, the abundance of the class Bacilli, order Lactobacillales, family Streptococcaceae, and genus Streptococcus was significantly higher than that in H. pylori-infected subjects without atrophic gastritis (FDR < 0.05). CONCLUSIONS: A significant increase in the relative abundance of several taxa was observed in gut microbiota of Japanese subjects with H. pylori infection. Among the subjects with severe atrophic gastritis, the increase in the genus Streptococcus is a remarkable characteristic.