Differences of microbiota in small bowel and faeces between irritable bowel syndrome patients and healthy subjects

Time-dependent gut microbiota analysis of juvenile Oreochromis niloticus by dietary supplementation of resveratrol

To evaluate the changes in bacterial diversity at various time points under resveratrol supplementation, we aimed to investigate the diversification of gut microbiota and the changes in total genetic diversity. We performed 16S rDNA gene sequencing at different time points (15, 30, and 45 days) to analyze the gut microbiota of tilapia. Fusobacteria, Proteobacteria, and Bacteroidetes (15 days) or Cyanobacteria (30 and 45 days) were found to be the three most abundant phyla. Cyanobacteria (15 and 30 days), Proteobacteria (15 days), Firmicutes and Chlamydiae (30 and 45 days), Planctomycetes (30 days), Bacteroidetes, Actinobacteria, and Fusobacteria (45 days) in the 0.05 g/kg RES group increased as compared to that in the controls. Proteobacteria and Cyanobacteria significantly decreased and increased at 30 and 45 days, respectively, while the reverse pattern was observed at 15 days. The Bacteroidetes:Firmicutes and Proteobacteria:Cyanobacteria ratios were significantly increased (15 and 45 days, P < 0.05) and decreased (30 days, P < 0.05). RES supplementation did not affect the richness and diversity of the gut microbiota in tilapia. Our findings may contribute to the development of strategies for the management of diseases.

Beneficial effect of butyrate-producing Lachnospiraceae on stress-induced visceral hypersensitivity in rats

BACKGROUND AND AIM

Emerging evidence indicates that psychological stress is involved in the pathogenesis of irritable bowel syndrome, which is characterized by visceral hypersensitivity and may be accompanied by gut dysbiosis. However, how such stress contributes to the development of visceral hypersensitivity is incompletely understood. Here, we aimed to investigate the influence that stress-induced microbial changes exert on visceral sensitivity, as well as the possible underlying mechanisms associated with this effect.

METHODS

Male Sprague-Dawley rats underwent chronic water avoidance stress (WAS) to induce visceral hypersensitivity. Visceral sensitivity, colonic tight junction protein expression, and short-chain fatty acids of cecal contents were measured. Fecal samples were collected to characterize microbiota profiles. In a separate study, oral gavage of Roseburia in WAS rats was conducted to verify its potential role in the effectiveness on visceral hypersensitivity.

RESULTS

Repeated WAS caused visceral hypersensitivity, altered fecal microbiota composition and function, and decreased occludin expression in the colon. Stressed rats exhibited reduced representation of pathways involved in the metabolism of butyrate and reduced abundance of several operational taxonomic units associated with butyrate-producing bacteria, such as Lachnospiraceae. Consistently, supplementation with Roseburia hominis, a species belonging to Lachnospiraceae, significantly increased cecal butyrate content. Moreover, Roseburia supplementation alleviated visceral hypersensitivity and prevented the decreased expression of occludin.

CONCLUSIONS

Reduction in the abundance of butyrate-producing Lachnospiraceae, which is beneficial for the intestinal barrier, was involved in the formation of visceral hypersensitivity. R. hominis is a potential probiotic for treating stress-induced visceral hypersensitivity.

The Structure and Function of the Human Small Intestinal Microbiota: Current Understanding and Future Directions

Despite growing literature characterizing the fecal microbiome and its association with health and disease, few studies have analyzed the microbiome of the small intestine. Here, we examine what is known about the human small intestinal microbiota in terms of community structure and functional properties. We examine temporal dynamics of select bacterial populations in the small intestine, and the effects of dietary carbohydrates and fats on shaping these populations. We then evaluate dysbiosis in the small intestine in several human disease models, including small intestinal bacterial overgrowth, short-bowel syndrome, pouchitis, environmental enteric dysfunction, and irritable bowel syndrome. What is clear is that the bacterial biology, and mechanisms of bacteria-induced pathophysiology, are enormously broad and elegant in the small intestine. Studying the small intestinal microbiota is challenged by rapidly fluctuating environmental conditions in these intestinal segments, as well as the complexity of sample collection and bioinformatic analysis. Because the functionality of the digestive tract is determined primarily by the small intestine, efforts must be made to better characterize this unique and important microbial ecosystem.

Second Asian Consensus on Irritable Bowel Syndrome

BACKGROUND/AIMS

There has been major progress in our understanding of the irritable bowel syndrome (IBS), and novel treatment classes have emerged. The Rome IV guidelines were published in 2016 and together with the growing body of Asian data on IBS, we felt it is timely to update the Asian IBS Consensus.

METHODS

Key opinion leaders from Asian countries were organized into 4 teams to review 4 themes: symptoms and epidemiology, pathophysiology, diagnosis and investigations, and lifestyle modifications and treatments. The consensus development process was carried out by using a modified Delphi method.

RESULTS

Thirty-seven statements were developed. Asian data substantiate the current global viewpoint that IBS is a disorder of gut-brain interaction. Socio-cultural and environmental factors in Asia appear to influence the greater overlap between IBS and upper gastrointestinal symptoms. New classes of treatments comprising low fermentable oligo-, di-, monosacharides, and polyols diet, probiotics, non-absorbable antibiotics, and secretagogues have good evidence base for their efficacy.

CONCLUSIONS

Our consensus is that all patients with functional gastrointestinal disorders should be evaluated comprehensively with a view to holistic management. Physicians should be encouraged to take a positive attitude to the treatment outcomes for IBS patients.

Gut Microbiota in Patients With Irritable Bowel Syndrome-A Systematic Review

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is common but difficult to treat. Altering the gut microbiota has been proposed as a strategy for treatment of IBS, but the association between the gut microbiome and IBS symptoms has not been well established. We performed a systematic review to explore evidence for this association.

METHODS

We searched databases, including MEDLINE, EMBASE, Cochrane CDSR, and CENTRAL, through April 2, 2018 for case-control studies comparing the fecal or colon microbiomes of adult or pediatric patients with IBS with microbiomes of healthy individuals (controls). The primary outcome was differences in specific gut microbes between patients with IBS and controls.

RESULTS

The search identified 2631 citations; 24 studies from 22 articles were included. Most studies evaluated adults presenting with various IBS subtypes. Family Enterobacteriaceae (phylum Proteobacteria), family Lactobacillaceae, and genus Bacteroides were increased in patients with IBS compared with controls, whereas uncultured Clostridiales I, genus Faecalibacterium (including Faecalibacterium prausnitzii), and genus Bifidobacterium were decreased in patients with IBS. The diversity of the microbiota was either decreased or not different in IBS patients compared with controls. More than 40% of included studies did not state whether cases and controls were comparable (did not describe sex and/or age characteristics).

CONCLUSIONS

In a systematic review, we identified specific bacteria associated with microbiomes of patients with IBS vs controls. Studies are needed to determine whether these microbes are a product or cause of IBS.

Composition of the mucosa-associated microbiota along the entire gastrointestinal tract of human individuals

Background

Homeostasis of the gastrointestinal tract depends on a healthy bacterial microbiota, with alterations in microbiota composition suggested to contribute to diseases. To unravel bacterial contribution to disease pathology, a thorough understanding of the microbiota of the complete gastrointestinal tract is essential. To date, most microbial analyses have either focused on faecal samples, or on the microbial constitution of one gastrointestinal location instead of different locations within one individual.

Objective

We aimed to analyse the mucosal microbiome along the entire gastrointestinal tract within the same individuals.

Methods

Mucosal biopsies were taken from nine different sites in 14 individuals undergoing antegrade and subsequent retrograde double-balloon enteroscopy. The bacterial composition was characterised using 16 S rRNA sequencing with Illumina Miseq.

Results

At double-balloon enteroscopy, one individual had a caecal adenocarcinoma and one individual had Peutz-Jeghers polyps. The composition of the microbiota distinctively changed along the gastrointestinal tract with larger bacterial load, diversity and abundance of Firmicutes and Bacteroidetes in the lower gastrointestinal tract than the upper gastrointestinal tract, which was predominated by Proteobacteria and Firmicutes.

Conclusions

We show that gastrointestinal location is a larger determinant of mucosal microbial diversity than inter-person differences. These data provide a baseline for further studies investigating gastrointestinal microbiota-related disease.

Small intestinal microbial dysbiosis underlies symptoms associated with functional gastrointestinal disorders

Small intestinal bacterial overgrowth (SIBO) has been implicated in symptoms associated with functional gastrointestinal disorders (FGIDs), though mechanisms remain poorly defined and treatment involves non-specific antibiotics. Here we show that SIBO based on duodenal aspirate culture reflects an overgrowth of anaerobes, does not correspond with patient symptoms, and may be a result of dietary preferences. Small intestinal microbial composition, on the other hand, is significantly altered in symptomatic patients and does not correspond with aspirate culture results. In a pilot interventional study we found that switching from a high fiber diet to a low fiber, high simple sugar diet triggered FGID-related symptoms and decreased small intestinal microbial diversity while increasing small intestinal permeability. Our findings demonstrate that characterizing small intestinal microbiomes in patients with gastrointestinal symptoms may allow a more targeted antibacterial or a diet-based approach to treatment.

Impact of Gut Dysbiosis on Neurohormonal Pathways in Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide major health problem. Traditional risk factors for CKD are hypertension, obesity, and diabetes mellitus. Recent studies have identified gut dysbiosis as a novel risk factor for the progression CKD and its complications. Dysbiosis can worsen systemic inflammation, which plays an important role in the progression of CKD and its complications such as cardiovascular diseases. In this review, we discuss the beneficial effects of the normal gut microbiota, and then elaborate on how alterations in the biochemical environment of the gastrointestinal tract in CKD can affect gut microbiota. External factors such as dietary restrictions, medications, and dialysis further promote dysbiosis. We discuss the impact of an altered gut microbiota on neuroendocrine pathways such as the hypothalamus⁻pituitary⁻adrenal axis, the production of neurotransmitters and neuroactive compounds, tryptophan metabolism, and the cholinergic anti-inflammatory pathway. Finally, therapeutic strategies including diet modification, intestinal alpha-glucosidase inhibitors, prebiotics, probiotics and synbiotics are reviewed.

Alterations of Gut Microbiota in Patients With Irritable Bowel Syndrome Based on 16S rRNA-Targeted Sequencing: A Systematic Review

INTRODUCTION

Alterations of gut microbiota have been thought to be associated with irritable bowel syndrome (IBS). Many studies have reported significant alterations of gut microbiota in patients with IBS based on 16S ribosomal RNA-targeted sequencing. However, results from these studies are inconsistent or even contradictory. We performed a systematic review to explore the alterations of gut microbiota in patients with IBS compared with healthy controls (HCs).

METHODS

The databases PubMed, Cochrane Library, Web of Science, and Embase were searched for studies published until February 28, 2018, for case-control studies detecting gut microbiota in patients with IBS. Methodological quality was assessed using the Newcastle-Ottawa Scale. The α-diversity and alterations of gut microbiota in patients with IBS compared with HCs were analyzed.

RESULTS

Sixteen articles involving 777 patients with IBS and 461 HCs were included. Quality assessment scores of the studies ranged from 5 to 7. For most studies, patients with IBS had a lower α-diversity than HCs in both fecal and mucosal samples. Relatively consistent changes in fecal microbiota for patients with IBS included increased Firmicutes, decreased Bacteroidetes, and increased Firmicutes:Bacteroidetes ratio at the phylum level, as well as increased Clostridia and Clostridiales, decreased Bacteroidia and Bacteroidales at lower taxonomic levels. Results for mucosal microbiota were inconsistent.

CONCLUSIONS

Alterations of gut microbiota exist in patients with IBS and have significant association with the development of IBS. Further studies are needed to draw conclusions about gut microbiota changes in patients with IBS.

TRANSLATIONAL IMPACT

This knowledge might improve the understanding of microbial signatures in patients with IBS and would guide future therapeutic strategies.

Lacto-fermented sauerkraut improves symptoms in IBS patients independent of product pasteurisation - a pilot study

Lacto-fermented sauerkraut contains a natural variety of lactic acid bacteria (LAB) and has not previously been studied in the treatment of irritable bowel syndrome (IBS) patients. The present study investigated the effect of a daily lacto-fermented sauerkraut supplement in relation to IBS patients' gastrointestinal symptoms and gut microbiota composition. A randomized double-blinded intervention was conducted with 34 Norwegian IBS patients. The patients were consuming either pasteurized sauerkraut (PS; n = 15) or unpasteurized sauerkraut (UPS; n = 19) as a supplement to their daily diet for 6 weeks. The differences in change of symptoms were assessed using the questionnaire IBS-Symptom Severity Score (IBS-SSS) measured at the baseline, and at weeks 2, 4, 6 and 8 (follow-up). The gut microbiota composition was analysed using 16S rRNA gene amplicon sequencing of faecal samples from the baseline and week 6. The mean change in IBS-SSS was -38.57 ± 17.08 PS vs. -56.99 ± 16.92 UPS and was significantly improved in both groups (P < 0.04), while the improvement in symptoms was not different between the intervention groups. The sauerkraut intervention (pasteurized or not) also led to significant gut microbiota compositional changes as determined by 16S rRNA gene amplicon sequencing (un-weighted UniFrac: P = 0.001, weighted UniFrac: P = 0.001). Sauerkraut related LAB in feces (Lactobacillus plantarum and Lactobacillus brevis) were significantly more often present in the UPS-group. In conclusion lacto-fermented sauerkraut had an effect on IBS patients' symptoms and gut microbiota even though the study was underpowered. Our results indicate that the observed effect to a larger extent can be attributed to the potential prebiotics in lacto-fermented sauerkraut rather than the viable LAB. Future studies with greater statistical power are needed to clarify the possible effects of LAB from lacto-fermented sauerkraut in the treatment of IBS patients.

A bacteriophage cocktail targeting Escherichia coli reduces E. coli in simulated gut conditions, while preserving a non-targeted representative commensal normal microbiota

Antibiotics offer an efficient means for managing diseases caused by bacterial pathogens. However, antibiotics are typically broad spectrum and they can indiscriminately kill beneficial microbes in body habitats such as the gut, deleteriously affecting the commensal gut microbiota. In addition, many bacteria have developed or are developing resistance to antibiotics, which complicates treatment and creates significant challenges in clinical medicine. Therefore, there is a real and urgent medical need to develop alternative antimicrobial approaches that will kill specific problem-causing bacteria without disturbing a normal, and often beneficial, gut microbiota. One such potential alternative approach is the use of lytic bacteriophages for managing bacterial infections, including those caused by multidrug-resistant pathogens. In the present study, we comparatively analysed the efficacy of a bacteriophage cocktail targeting Escherichia coli with that of a broad-spectrum antibiotic (ciprofloxacin) using an in vitro model of the small intestine. The parameters examined included (i) the impact on a specific, pre-chosen targeted E. coli strain, and (ii) the impact on a selected non-targeted bacterial population, which was chosen to represent a defined microbial consortium typical of a healthy small intestine. During these studies, we also examined stability of bacteriophages against various pH and bile concentrations commonly found in the intestinal tract of humans. The bacteriophage cocktail was slightly more stable in the simulated duodenum conditions compared to the simulated ileum (0.12 vs. 0.58 log decrease in phage titers, respectively). It was equally effective as ciprofloxacin in reducing E. coli in the simulated gut conditions (2-3 log reduction), but had much milder (none) impact on the commensal, non-targeted bacteria compared to the antibiotic.

Hypoxia-induced intestinal barrier changes in balloon-assisted enteroscopy

KEY POINTS

Balloon-assisted enteroscopy (BAE) is an emerging standard procedure by utilizing distensible balloons to facilitate deep endoscopy in the small and large intestine. Sporadic cases of bacteraemia were found after BAE. Balloon distension by BAE caused gut tissue hypoxia. The impact of balloon distension-induced hypoxia on intestinal barriers remains unclear. Murine models of BAE by colonic balloon distension showed that short- and long-term hypoxia evoked opposite effects on epithelial tight junctions (TJs). Short-term hypoxia fortified TJ integrity, whereas long-term hypoxia caused damage to barrier function. Our data showed for the first time the molecular mechanisms and signalling pathways of epithelial barrier fortification and TJ reorganization by short-term hypoxia for the maintenance of gut homeostasis. The findings suggest avoiding prolonged balloon distension during BAE to reduce the risk of hypoxia-induced gut barrier dysfunction.

ABSTRACT

Balloon-assisted enteroscopy (BAE) is an emerging standard procedure that uses distensible balloons to facilitate deep endoscopy. Intestines are known to harbour an abundant microflora. Whether balloon distension causes perturbation of blood flow and gut barrier dysfunction, and elicits risk of bacterial translocation remains unknown. Our aims were to (1) conduct a prospective study to gather microbiological and molecular evidence of bacterial translocation by BAE in patients, (2) establish a murine model of colonic balloon distension to investigate tissue hypoxia and intestinal barrier, and (3) assess the effect of short- and long-term hypoxia on epithelial permeability using cell lines. Thirteen patients were enrolled for BAE procedures, and blood samples were obtained before and after BAE for paired comparison. Four of the 13 patients (30.8%) had positive bacterial DNA in blood after BAE. Post-BAE endotoxaemia was higher than the pre-BAE level. Nevertheless, no clinical symptom of sepsis or fever was reported. To mimic clinical BAE, mice were subjected to colonic balloon distension. Local tissue hypoxia was observed during balloon inflation, and reoxygenation after deflation. A trend of increased gut permeability was seen after long-term distension, whereas a significant reduction of permeability was observed by short-term distension in the proximal colon. Human colonic epithelial Caco-2 cells exposed to hypoxia for 5-20 min exhibited increased tight junctional assembly, while those exposed to longer hypoxia displayed barrier disruption. In conclusion, sporadic cases of bacteraemia were found after BAE, without septic symptoms. Short-term hypoxia by balloon distension yielded a protective effect whereas long-term hypoxia caused damage to the gut barrier.

Role of Gut Microbiota-Gut Hormone Axis in the Pathophysiology of Functional Gastrointestinal Disorders

Gut microbiota exert a pivotal influence on various functions including gastrointestinal (GI) motility, metabolism, nutrition, immunity, and the neuroendocrine system in the host. These effects are mediated by not only short-chain fatty acids produced by microbiota but also gut hormones and inflammatory signaling by enteroendocrine and immune cells under the influence of the microbiota. GI motility is orchestrated by the enteric nervous system and hormonal networks, and disturbance of GI motility plays an important role in the pathophysiology of functional gastrointestinal disorders (FGIDs). In this context, microbiota-associated mediators are considered to act on specific receptors, thus affecting the enteric nervous system and, subsequently, GI motility. Thus, the pathophysiology of FGIDs is based on alterations of the gut microbiota/gut hormone axis, which have crucial effects on GI motility.

Involvement of shared mucosal-associated microbiota in the duodenum and rectum in diarrhea-predominant irritable bowel syndrome

BACKGROUND AND AIM

Most studies of diarrhea-predominant irritable bowel syndrome (IBS-D) focused on microbiota dysbiosis in a single segment of the intestine such as the colon. However, the intestine as a whole is involved in IBS-D and knowledge about the role of microbiota shared by the duodenum and rectum in IBS-D is limited. Here, we investigated the characteristics of mucosal microbiota shared by the duodenum and rectum in IBS-D patients.

METHODS

We collected duodenal and rectal mucosal samples from 33 adult IBS-D patients and 15 healthy control (HC) subjects. The 454 pyrosequencing method and multiple bioinformatics analyses were used to examine bacterial 16S rRNA. Clinical data including symptoms and Bristol Stool Form were analyzed.

RESULTS

Mucosal microbiota in duodenal samples differed from rectal samples in HC, while less difference was shown in IBS-D. More numbers in terms of shared operational taxonomic units and genera found in IBS-D compared with HC. The frequency of genera in the duodenum and rectum of HC differed from that of IBS-D. We identified 24 genera shared in the duodenum and rectum, which both changed dramatically in IBS-D. Among these 24 genera, half had similar trends in frequency differences, and the other half had opposite trends. The frequency of Faecalibacterium and Hyphomicrobium were associated with clinical data of IBS-D patients.

CONCLUSIONS

Shared mucosal-associated microbiota in the duodenum and rectum appear to contribute to the etiology and pathophysiology of whole intestine of IBS-D and to be potential therapeutic targets.

Interplay of host genetics and gut microbiota underlying the onset and clinical presentation of inflammatory bowel disease

OBJECTIVE

Patients with IBD display substantial heterogeneity in clinical characteristics. We hypothesise that individual differences in the complex interaction of the host genome and the gut microbiota can explain the onset and the heterogeneous presentation of IBD. Therefore, we performed a case-control analysis of the gut microbiota, the host genome and the clinical phenotypes of IBD.

DESIGN

Stool samples, peripheral blood and extensive phenotype data were collected from 313 patients with IBD and 582 truly healthy controls, selected from a population cohort. The gut microbiota composition was assessed by tag-sequencing the 16S rRNA gene. All participants were genotyped. We composed genetic risk scores from 11 functional genetic variants proven to be associated with IBD in genes that are directly involved in the bacterial handling in the gut: NOD2, CARD9, ATG16L1, IRGM and FUT2.

RESULTS

Strikingly, we observed significant alterations of the gut microbiota of healthy individuals with a high genetic risk for IBD: the IBD genetic risk score was significantly associated with a decrease in the genus Roseburia in healthy controls (false discovery rate 0.017). Moreover, disease location was a major determinant of the gut microbiota: the gut microbiota of patients with colonic Crohn's disease (CD) is different from that of patients with ileal CD, with a decrease in alpha diversity associated to ileal disease (p=3.28×10^-13).

CONCLUSIONS

We show for the first time that genetic risk variants associated with IBD influence the gut microbiota in healthy individuals. Roseburia spp are acetate-to-butyrate converters, and a decrease has already been observed in patients with IBD.

The gastrointestinal microbiota and its role in oncogenesis

Advances in research techniques have made it possible to map the microbial communities in the gastrointestinal (GI) tract, where the majority of bacteria in the human body reside. Disturbances in these communities are referred to as dysbiosis and have been associated with GI cancers. Although dysbiosis is observed in several GI malignancies, the specific role of these changes has not been understood to the extent of Helicobacter pylori (HP) in gastric cancer (GC). This review will address the bacterial communities along the GI tract, from the oral cavity to the anal canal, particularly focusing on bacterial dysbiosis and carcinogenesis. Just as non-HP bacteria in the stomach may interact with HP in gastric carcinogenesis, the same may hold true for other GI tract malignancies, where an interplay between microbes in carcinogenesis seems conceivable, especially in colorectal cancer (CRC). In the last part of this review we will discuss the potential mechanisms of bacterial dysbiosis in GI carcinogenesis.

[Therapeutic modulation of intestinal microbiota in irritable bowel syndrome. From probiotics to fecal microbiota therapy]

BACKGROUND

An abnormal intestinal microbiota (dysbiosis) plays a central role in the pathogenesis of the irritable bowel syndrome.

METHOD

An overview of four current options for the treatment of irritable bowel syndrome, which are characterized by modulation of intestinal microbiota, is given.

RESULTS AND CONCLUSIONS

Probiotics have very different effects on the individual symptoms of the irritable bowel. The choice of the appropriate preparation should therefore be based on the clinical symptomatology. The antibiotic rifaximin is effective in selected patients. Some patients also benefit from the repetition of this therapy. A FODMAP-reduced diet has shown significant alleviation of irritable bowel symptoms in studies. The fecal microbiota therapy (FMT) is a promising treatment option. At present, however, there are no such placebo-controlled studies to assess the effectiveness of this method.

From clinical uncertainties to precision medicine: the emerging role of the gut barrier and microbiome in small bowel functional diseases

Over the last decade, remarkable progress has been made in the understanding of disease pathophysiology. Many new theories expound on the importance of emerging factors such as microbiome influences, genomics/omics, stem cells, innate intestinal immunity or mucosal barrier complexities. This has introduced a further dimension of uncertainty into clinical decision-making, but equally, may shed some light on less well-understood and difficult to manage conditions. Areas covered: Comprehensive review of the literature on gut barrier and microbiome relevant to small bowel pathology. A PubMed/Medline search from 1990 to April 2017 was undertaken and papers from this range were included. Expert commentary: The scenario of clinical uncertainty is well-illustrated by functional gastrointestinal disorders (FGIDs). The movement towards achieving a better understanding of FGIDs is expressed in the Rome IV guidelines. Novel diagnostic and therapeutic protocols focused on the GB and SB microbiome can facilitate diagnosis, management and improve our understanding of the underlying pathological mechanisms in FGIDs.

Small intestinal bacterial overgrowth as a cause for irritable bowel syndrome: guilty or not guilty?

PURPOSE OF REVIEW

Small intestinal bacterial overgrowth (SIBO) has been proposed as a cause of irritable bowel syndrome (IBS). However, this relationship has been subject to controversy. This review aims to provide a current perspective on the SIBO-IBS hypothesis.

RECENT FINDINGS

Case-control studies evaluating the prevalence of SIBO in IBS and healthy individuals have shown conflicting results. Moreover, the tests available in routine clinical practice to diagnose SIBO are not valid and lack both sensitivity and specificity. Hence, interpreting the effect of interventions based on these tests is fraught with uncertainty. Furthermore, the SIBO-IBS hypothesis has paved the way to assess antibiotic therapy in nonconstipated IBS, with rifaximin, a nonabsorbable antibiotic, showing modest but significant clinical benefit. However, individuals were not tested for SIBO and the mechanism of action of rifaximin in IBS remains to be elucidated. Preliminary data suggest that rifaximin decreases microbial richness and previous studies have noted antibacterial interventions in IBS to reduce colonic fermentation and improve symptoms. The advent of rapid culture-independent molecular techniques is a promising tool that will seek to clarify and advance our understanding of the gut microbial function.

SUMMARY

The SIBO-IBS hypothesis lacks convincing evidence but remains under scrutiny. The mechanism resulting in symptom improvement after rifaximin treatment in some IBS individuals requires exploration. Novel molecular techniques provide an exciting and challenging opportunity to explore the host-gut microbiota interaction.

Mind-Body Interventions for Pediatric Inflammatory Bowel Disease

Pediatric inflammatory bowel disease is an autoimmune disease that causes chronic inflammation of the gastrointestinal mucosa. There is emerging evidence that the brain–gut connection affects inflammatory bowel disease (IBD) patients more than previously thought. This is evidenced by comorbid mood disorders, irritable bowel symptoms concurrent with quiescent IBD, and the potential of psychosocial stressors to trigger IBD flares. Mind–body interventions such as psychotherapy, relaxation, mindfulness, biofeedback, yoga, and clinical hypnosis offer an adjunct to standard medical treatment for IBD. We will review the current evidence base for these mind–body interventions in the treatment of pediatric IBD, illustrate a case study, and offer suggestions for future research for this promising field.

Mucosal pathobiology and molecular signature of epithelial barrier dysfunction in the small intestine in irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most prevalent gastrointestinal disorders in developed countries. Its etiology remains unknown; however, a common finding, regardless of IBS subtype, is the presence of altered intestinal barrier. In fact, signaling and location of cell-to-cell adhesion proteins, in connection with increased immune activity, seem abnormal in the intestinal epithelium of IBS patients. Despite that most research is performed on distal segments of the intestine, altered permeability has been reported in both, the small and the large bowel of all IBS subtypes. The small intestine carries out digestion and nutrient absorption and is also the site where the majority of immune responses to luminal antigens takes place. In fact, the upper intestine is more exposed to environmental antigens than the colon and is also a site of symptom generation. Recent studies have revealed small intestinal structural alterations of the epithelial barrier and mucosal immune activation in association with intestinal dysfunction, suggesting the commitment of the intestine as a whole in the pathogenesis of IBS. This review summarizes the most recent findings on mucosal barrier alterations and its relationship to symptoms arising from the small intestine in IBS, including epithelial structural abnormalities, mucosal immune activation, and microbial dysbiosis, further supporting the hypothesis of an organic origin of IBS.

Effects of plant fermentation extract on intestinal microbiota in patients with irritable bowel syndrome

AIM: To investigate the effect of plant fermentation extracts (PFE) on intestinal microbiota in patients with irritable bowel syndrome (IBS), using high-throughput sequencing.

METHODS: The feces were collected from IBS patients before (day 0) and 30 days (day 30) after consumption of PFE, respectively. The community structure and abundance of the intestinal microbiota were examined via analyzing 16S rRNA high throughput sequencing using an Illumima System.

RESULTS: The overall diversity of the intestinal microbiota had no significant change on day 30. At the phylum level, the abundance of Firmicutes was significantly decreased (P < 0.05), while that of Bacteroidetes was significantly increased (P < 0.05). The ratio of Bacteroidetes/Firmicutes was greatly elevated. At the family level, Campylobacteraceae, Cryomorphaceae, Erysipelotrichaceae and Fibrobacteraceae were detected after the PFE consumption, and their abundance all significantly increased (P < 0.05).

CONCLUSION: PFE improves the abundance of intestinal microbiota in IBS patients, which may be utilized as a type of dietary intervention of IBS.

Gastrointestinal and hepatic mechanisms limiting entry and dissemination of lipopolysaccharide into the systemic circulation

The human microbiota consists of 100 trillion microorganisms that provide important metabolic and biological functions benefiting the host. However, the presence in host plasma of a gut-derived bacteria component, the lipopolysaccharide (LPS), has been identified as a causal or complicating factor in multiple serious diseases such as sepsis and septic shock and, more recently, obesity-associated metabolic disorders. Understanding the precise mechanisms by which gut-derived LPS is transported from the gut lumen to the systemic circulation is crucial to advance our knowledge of LPS-associated diseases and elaborate targeted strategies for their prevention. The aim of this review is to synthetize current knowledge on the host mechanisms limiting the entry and dissemination of LPS into the systemic circulation. To prevent bacterial colonization and penetration, the intestinal epithelium harbors multiple defense mechanisms including the secretion of antimicrobial peptides and mucins as well as detoxification enzymes. Despite this first line of defense, LPS can reach the apical site of intestinal epithelial cells (IECs) and, because of its large size, likely crosses IECs via transcellular transport, either lipid raft- or clathrin-mediated endocytosis or goblet cell-associated passage. However, the precise pathway remains poorly described. Finally, if LPS crosses the gut mucosa, it is directed via the portal vein to the liver, where major detoxification processes occur by deacetylation and excretion through the bile. If this disposal process is not sufficient, LPS enters the systemic circulation, where it is handled by numerous transport proteins that clear it back to the liver for further excretion.