Faecal microbiota composition and host-microbe cross-talk following gastroenteritis and in postinfectious irritable bowel syndrome

Microbiota-neuroimmune cross talk in stress-induced visceral hypersensitivity of the bowel

Visceral hypersensitivity of the lower gastrointestinal tract, defined as an increased response to colorectal distension, frequently prompts episodes of debilitating abdominal pain in irritable bowel syndrome (IBS). Although the pathophysiology of IBS is not yet fully elucidated, it is well known that stress is a major risk factor for development and acts as a trigger of pain sensation. Stress modulates both immune responses as well as the gut microbiota and vice versa. Additionally, either microbes themselves or through involvement of the immune system, activate or sensitize afferent nociceptors. In this paper, we review current knowledge on the influence of stress along the gut-brain-microbiota axis and exemplify relevant neuroimmune cross talk mechanisms in visceral hypersensitivity, working toward understanding how gut microbiota-neuroimmune cross talk contributes to visceral pain sensation in IBS patients.

Efficacy and Safety of Probiotics in Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis

Background

Irritable bowel syndrome is a functional gastrointestinal disease. Evidence has suggested that probiotics may benefit IBS symptoms. However, clinical trials remain conflicting.

Aims

To implement a systematic review and meta-analysis of clinical trials regarding the efficacy and safety of probiotics for IBS patients.

Methods

We searched for relevant trials in Medline(1966 to Jan 2019), Embase(1974 to Jan 2019), the Cochrane Central Register of Controlled Trials(up to Jan 2019), the ClinicalTrials.gov trials register(up to Jan 2019), and Chinese Biomedical Literature Database(1978 to Jan 2019). Risk ratio (RR) and a 95% confidence interval (CI) were calculated for dichotomous outcomes. Standardized mean difference (SMD) and 95% CI were calculated for continuous outcomes.

Results

A total of 59 studies, including 6,761 patients, were obtained. The RR of the improvement or response with probiotics versus placebo was 1.52 (95% CI 1.32-1.76), with significant heterogeneity (I² = 71%, P < 0.001). The SMD of Probiotics in improving global IBS symptoms vs. Placebo was -1.8(95% CI -0.30 to -0.06), with significant heterogeneity (I² = 65%, P < 0.001). It was impossible to draw a determinate conclusion. However, there were differences in subgroup analyses of probiotics type, dose, treatment duration, and geographic position. Probiotics seem to be safe by the analysis of adverse events(RR = 1.07; 95% CI 0.92-1.24; I² = 0, P = 0.83).

Conclusion

Probiotics are effective and safe for IBS patients. Single probiotics with a higher dose (daily dose of probiotics ≥10¹⁰) and shorter duration (< 8 weeks) seem to be a better choice, but it still needs more trials to prove it.

Feeling down? A systematic review of the gut microbiota in anxiety/depression and irritable bowel syndrome

Background Anxiety/depression and irritable bowel syndrome (IBS) are highly prevalent and burdensome conditions, whose co-occurrence is estimated between 44 and 84%. Shared gut microbiota alterations have been identified in these separate disorders relative to controls; however, studies have not adequately considered their comorbidity. This review set out to identify case-control studies comparing the gut microbiota in anxiety/depression, IBS, and both conditions comorbidly relative to each other and to controls, as well as gut microbiota investigations including measures of both IBS and anxiety/depression. Methods Four databases were systematically searched using comprehensive search terms (OVID Medline, Embase, PsycINFO, and PubMed), following PRISMA guidelines. Results Systematic review identified 17 studies (10 human, 7 animal). Most studies investigated the gut microbiota and anxiety/depression symptoms in IBS cohorts. Participants with IBS and high anxiety/depression symptoms had lower alpha diversity compared to controls and IBS-only cohorts. Machine learning and beta diversity distinguished between IBS participants with and without anxiety/depression by their gut microbiota. Comorbid IBS and anxiety/depression also had higher abundance of Proteobacteria, Prevotella/Prevotellaceae, Bacteroides and lower Lachnospiraceae relative to controls. Limitations A large number of gut microbiota estimation methods and statistical techniques were utilized; therefore, meta-analysis was not possible. Conclusions Well-designed case-control and longitudinal studies are required to disentangle whether the gut microbiota is predicted as a continuum of gastrointestinal and anxiety/depression symptom severity, or whether reported dysbiosis is unique to IBS and anxiety/depression comorbidity. These findings may inform the development of targeted treatment through the gut microbiota for individuals with both anxiety/depression and IBS.

The Evolving Role of Gut Microbiota in the Management of Irritable Bowel Syndrome: An Overview of the Current Knowledge

The intestinal microbiota is one of the most rapidly evolving areas in biology and medicine. Extensive research in the last decade has escalated our understanding of the role of the microbiota in the pathogenesis of several intestinal and extra-intestinal disorders. Marked by high prevalence, substantial morbidity, and enormous costs, irritable bowel syndrome (IBS) is an important chronic gastrointestinal disorder that is widely encountered by gastroenterologists. Despite advances in our understanding of its pathophysiology, curative interventions have yet to be discovered, and therapeutic approaches remain symptom-driven. Recently, accumulating evidence has enlightened the possible impact of an imbalanced gut microbiome in the pathogenesis of IBS. In fact, several studies have documented altered microbiota in patients, while others have shown that IBS severity was associated with a distinct microbiota signature. These findings may pave the way for the use of microbiota manipulation strategies as an attractive option for IBS management, and may have an essential role in efforts to reduce the societal and economic effects of this ever-growing disorder. In this review, we have outlined the results of the latest research on the association between microbiota and IBS and their implications for the clinical management of affected patients.

Efficacy and safety of probiotics in irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND/AIM

Irritable Bowel Syndrome (IBS) is a common chronic functional bowel disorder and the evidence shows most drug therapies in the treatment of IBS are weak. Recently, some studies showed probiotics may have a positive effect in IBS and they are widely used to improve the symptom of IBS, which indicate probiotics may play an important role in the treatment of IBS. However, the exact effectiveness and safety of probiotics are largely unknown. This systematic review focuses on identifying the efficacy and safety of probiotics in the treatment of IBS.

MATERIALS AND METHODS

Data sources were searched up to February 2019. Databases included MEDLINE, CENTRAL, CINAHL, and Embase. Randomized controlled trials (RCTs) comparing probiotics including complex or individual probiotics with placebo or no therapy were screened, extracted, and appraised by two independent reviewers. The data were pooled using a random-effects model. The methodological quality of all RCTs was assessed using the Cochrane risk of bias and Jadad scale. Outcomes included symptom-relevant and patient-relevant characteristics, such as symptom relief, abdominal pain, bloating, flatulence, quality of life, and adverse event.

RESULTS

This review includes 28 studies with a total of 3606 participants. Particular combinations of probiotics, or specific species and strains, showed probiotics have beneficial effect on overall IBS symptoms (22 studies, n = 3144, RR of improvement in overall IBS symptoms = 1.5, CI 1.23 to 1.83) or overall IBS symptom and abdominal pain scores (18 studies, n = 2766, SMD = -0.31, CI -0.45 to -0.17). In addition, adverse events were not significantly higher with probiotics (8 studies, n = 923, RR = 1.05; 95% CI 0.85-1.31). However, there was no significant benefit on individual IBS symptom scores and quality of life.

CONCLUSION

Current evidence shows particular combinations, species or strains of probiotics are effective for overall IBS symptoms. However, it is hard to derive a definite conclusion due to high heterogeneity and unclear risk of bias of some trials. Large well-designed and rigorous trials are warranted.

Naturally Occurring TPE-CA Maintains Gut Microbiota and Bile Acids Homeostasis via FXR Signaling Modulation of the Liver-Gut Axis

Antibiotics-induced changes in intestinal flora (dysbiosis) may have various effects on the host. Dysbiosis is associated with numerous metabolites including bile acids, which are produced in the liver from cholesterol and metabolized in the gut by intestinal microbiota. Total phenolic extracts of Citrus aurantium L. (TPE-CA) are rich in dietary flavanones and their glycosyl derivatives, including flavones, flavonols, polymethoxyflavones and coumarins, which exert positive health effects on the microbiota. The aim of this study is to elucidate the interplays between the intestinal microbiota and bile acids metabolism attributed to antibiotics. Mice were exposed to broad-spectrum antibiotics, such as ampicillin, streptomycin and clindamycin, for 14 days. This exposure resulted in reduced bacterial diversity and richness, and destroyed intestinal permeability. The homeostasis of bile acids was also affected. Subsequent TPE-CA administration, counteracted most of the dysbiosis, and reshaped intestinal permeability, these effects occurred via upregulation of zonula occludens 1 and occludin associated proteins and downregulation of serum endotoxin compared to the antibiotics group. TPE-CA maintained the homeostasis of bile acids via modulation of the liver-gut axis related farnesoid X receptor (FXR)/fibroblast growth factor 15 (FGF15) pathway and FXR-targeted protein. Our findings indicated that TPE-CA exerted a protective effect on the restoration of intestinal microbiota composition, reshaped barrier integrity and maintained bile acid homeostasis via the liver-gut axis with antibiotics-induced dysbiosis.

Peroxiredoxin 1 as an inflammatory marker in diarrhea-predominant and postinfectious irritable bowel syndrome

BACKGROUND

Low-grade inflammation occurs in some patients with irritable bowel syndrome (IBS). However, the exact inflammatory markers of IBS and the relationship of these markers with IBS subtypes and symptoms are poorly defined. Peroxiredoxin 1 (PRDX1) plays an important role in inflammatory responses, including intestinal inflammation. We investigated whether PRDX1 is associated with the diagnosis, subtypes, and symptom severity of IBS.

METHODS

A total of 177 IBS patients and 174 sex- and age-matched healthy controls (HCs) were recruited. The PRDX1 levels in the sera and colonic mucosa of the participants were detected by enzyme-linked immunosorbent assays and immunohistochemistry. The severity of IBS symptoms was assessed using the IBS Severity Scoring System (SSS) questionnaire.

RESULTS

The PRDX1 levels in the sera (F = 71.81, P < .001) and colonic mucosa (F = 5.359, P < .001) of postinfectious (PI-IBS) and diarrhea-predominant IBS (IBS-D) groups were significantly higher than those of the other three IBS subtypes and HC group. The PRDX1 level in the serum and colonic mucosa of IBS-D (serum, P < .01, mucosa, P < .001) and PI-IBS (serum, P < .05, mucosa, P < .001) groups with the most severe symptoms was significantly higher than that in the groups with mild and moderate symptoms. Correlation analysis revealed that in patients with IBS-D (P < .001) and PI-IBS (P < .05), the levels of PRDX1 and TNF-α in sera had a significant positive correlation with IBS-SSS.

CONCLUSION

Elevated PRDX1 in the serum and colon mucosa may be closely related to the progression of IBS (especially IBS-D and PI-IBS) and the expression of gastrointestinal symptoms.

Irritable Bowel Syndrome between Molecular Approach and Clinical Expertise-Searching for Gap Fillers in the Oxidative Stress Way of Thinking

Irritable bowel syndrome (IBS) remains to date an intriguing functional gastrointestinal disorder. Recent studies described a multitude of exogenous factors that work together in IBS, gradually impairing intestinal lining cellular metabolism, including oxidative status balance, with or without a genetic background. Although the current biomarkers support the differentiation between IBS subtypes and other functional gastrointestinal disorder, they are mostly non-specific, referring to clinical, biochemical, and inflammatory imbalances. Since IBS could be also the result of deficient signaling pathways involving both gastrointestinal secretion and neuro-vegetative stimulation, IBS makes no exception from the oxidative hypothesis in the pathological mechanisms. Regarding the oxidative stress implication in IBS, the previous research efforts showed controversial results, with some animal models and patient studies reporting clear oxidative imbalance both on systemic and local levels, but still with no concrete evidence to point to a direct correlation between oxidative stress and IBS. Additionally, it seems that a major role could be also attributed to gut microbiota and their ability to shape our bodies and behaviors. Moreover, the genetic features study in IBS patients showed that several genetic similarities point to a possible correlation of IBS with affective spectrum disorders. Thus, we focus here the discussion on the assumption that IBS could in fact be more likely a stress-related disorder rather than a gastrointestinal one.

Evidence of altered mucosa-associated and fecal microbiota composition in patients with Irritable Bowel Syndrome

Altered bacterial composition and small intestinal bacterial overgrowth (SIBO) may be associated with irritable bowel syndrome (IBS). This study aimed to determine the fecal and mucosa-associated bacterial composition along the gastrointestinal (GI) tract and to assess SIBO in IBS. Bacterial composition of feces, and mucosa of the duodenum and sigmoid colon was determined by 16S rRNA-amplicon-sequencing. SIBO was evaluated by bacterial culture of duodenal aspirate, glucose and lactulose breath tests. Mucosal antibacterial gene expression was assessed by PCR Array. The bacterial profiles of feces and the mucosa of sigmoid colon, but not duodenum, differed between IBS patients (n = 17) and HS (n = 20). The IBS specific bacterial profiles were linked to the colonic antibacterial gene expression. Fecal bacterial profile differed between IBS subtypes, while the mucosa-associated bacterial profile was associated with IBS symptom severity and breath tests results at baseline (H₂ and/or CH₄ ≥ 15 ppm). The prevalence of SIBO was similar between IBS patients and HS. This study demonstrates that alterations in the bacterial composition of the sigmoid colon of IBS patients were linked to symptoms and immune activation. While breath tests reflected the mucosa-associated bacterial composition, there was no evidence for high prevalence of SIBO or small intestinal bacterial alterations in IBS.

Clinical Management of the Microbiome in Irritable Bowel Syndrome

Background

A growing body of evidence suggests that dysbiosis contributes to the onset and symptomatology of irritable bowel syndrome (IBS) and other functional bowel disorders. Changes to the gastrointestinal microbiome may contribute to the underlying pathophysiology of IBS.

Methods

The present review summarizes the potential effects of microbiome changes on GI transit, intestinal barrier function, immune dysregulation and inflammation, gut–brain interactions and neuropsychiatric function.

Results

A multimodal approach to IBS management is recommended in accordance with current Canadian guidelines. Pharmacologic treatments are advised to target the presumed underlying pathophysiological mechanism, such as dysregulation of GI transit, peristalsis, intestinal barrier function and pain signalling. The management plan for IBS may also include treatments directed at dysbiosis, including dietary modification and use of probiotics, which may promote the growth of beneficial bacteria, affect intestinal gas production and modulate the immune response; and the administration of periodic short courses of a nonsystemic antibiotic such as rifaximin, which may re-establish microbiota diversity and improve IBS symptoms.

Conclusion

Dysregulated host–microbiome interactions are complex and the use of microbiome-directed therapies will necessarily be empiric in individual patients. A management algorithm comprising microbiome- and nonmicrobiome-directed therapies is proposed.

Role of Gut Dysbiosis in Liver Diseases: What Have We Learned So Far?

Accumulating evidence supports that gut dysbiosis may relate to various liver diseases. Alcoholics with high intestinal permeability had a decrease in the abundance of Ruminnococcus. Intestinal dysmotility, increased gastric pH, and altered immune responses in addition to environmental and genetic factors are likely to cause alcohol-associated gut microbial changes. Alcohol-induced dysbiosis may be associated with gut barrier dysfunction, as microbiota and their products modulate barrier function by affecting epithelial pro-inflammatory responses and mucosal repair functions. High levels of plasma endotoxin are detected in alcoholics, in moderate fatty liver to advanced cirrhosis. Decreased abundance of Faecalibacterium prausnitzii, an anti-inflammatory commensal, stimulating IL-10 secretion and inhibiting IL-12 and interferon-γ expression. Proteobacteria, Enterobacteriaceae, and Escherichia were reported to be increased in NAFLD (nonalcoholic fatty liver disease) patients. Increased abundance of fecal Escherichia to elevated blood alcohol levels in these patients and gut microbiota enriched in alcohol-producing bacteria produce more alcohol (alcohol hypothesis). Some undetermined pathological sequences related to gut dysbiosis may facilitate energy-producing and proinflammatory conditions for the progression of NAFLD. A shortage of autochthonous non-pathogenic bacteria and an overgrowth of potentially pathogenic bacteria are common findings in cirrhotic patients. The ratio of the amounts of beneficial autochthonous taxa (Lachnospiraceae + Ruminococaceae + Veillonellaceae + Clostridiales Incertae Sedis XIV) to those of potentially pathogenic taxa (Enterobacteriaceae + Bacteroidaceae) was low in those with early death and organ failure. Cirrhotic patients with decreased microbial diversity before liver transplantation were more likely to develop post-transplant infections and cognitive impairment related to residual dysbiosis. Patients with PSC had marked reduction of bacterial diversity. Enterococcus and Lactobacillus were increased in PSC patients (without liver cirrhosis.) Treatment-naive PBC patients were associated with altered composition and function of gut microbiota, as well as a lower level of diversity. As serum anti-gp210 antibody has been considered as an index of disease progression, relatively lower species richness and lower abundance of Faecalibacterium spp. in gp210-positive patients are interesting. The dysbiosis-induced altered bacterial metabolites such as a hepatocarcinogenesis promotor DCA, together with a leaky gut and bacterial translocation. Gut protective Akkermansia and butyrate-producing genera were decreased, while genera producing-lipopolysaccharide were increased in early hepatocellular carcinoma (HCC) patients.

The human gut bacteria Christensenellaceae are widespread, heritable, and associated with health

The Christensenellaceae, a recently described family in the phylum Firmicutes, is emerging as an important player in human health. The relative abundance of Christensenellaceae in the human gut is inversely related to host body mass index (BMI) in different populations and multiple studies, making its relationship with BMI the most robust and reproducible link between the microbial ecology of the human gut and metabolic disease reported to date. The family is also related to a healthy status in a number of other different disease contexts, including obesity and inflammatory bowel disease. In addition, Christensenellaceae is highly heritable across multiple populations, although specific human genes underlying its heritability have so far been elusive. Further research into the microbial ecology and metabolism of these bacteria should reveal mechanistic underpinnings of their host-health associations and enable their development as therapeutics.

Fecal microbiota transplantation in irritable bowel syndrome: A systematic review and meta-analysis

Background

Modulating gut microbiota is a potential treatment for irritable bowel syndrome (IBS). This meta-analysis explored whether fecal microbiota transplantation (FMT) is successful in treating IBS.

Methods

A systematic review was performed to find trials on FMT in IBS. Ratios and relative ratios (RR) of improvement for single-arm trials (SATs) and randomized controlled trials (RCTs) were calculated, respectively. Changes in IBS Severity Scoring System (IBS-SSS) and IBS Quality of Life (IBS-QOL) instrument compared to baseline in FMT versus placebo groups were pooled.

Results

In SATs, 59.5% (95% confidence interval (CI) 49.1-69.3) of IBS patients showed significant improvement. In RCTs, there were no differences between FMT and control in improvement (RR=0.93 (95% CI 0.50-1.75)) or changes in the IBS-SSS and IBS-QOL.

Conclusions

FMT was not effective in IBS. Variations in FMT methods and patient factors may contribute to the heterogeneous results of the trials.

Microbiota: a novel regulator of pain

Among the various regulators of the nervous system, the gut microbiota has been recently described to have the potential to modulate neuronal cells activation. While bacteria-derived products can induce aversive responses and influence pain perception, recent work suggests that "abnormal" microbiota is associated with neurological diseases such as Alzheimer's, Parkinson's disease or autism spectrum disorder (ASD). Here we review how the gut microbiota modulates afferent sensory neurons function and pain, highlighting the role of the microbiota/gut/brain axis in the control of behaviors and neurological diseases. We outline the changes in gut microbiota, known as dysbiosis, and their influence on painful gastrointestinal disorders. Furthermore, both direct host/microbiota interaction that implicates activation of "pain-sensing" neurons by metabolites, or indirect communication via immune activation is discussed. Finally, treatment options targeting the gut microbiota, including pre- or probiotics, will be proposed. Further studies on microbiota/nervous system interaction should lead to the identification of novel microbial ligands and host receptor-targeted drugs, which could ultimately improve chronic pain management and well-being.

The study evaluating the effect of probiotic supplementation on the mental status, inflammation, and intestinal barrier in major depressive disorder patients using gluten-free or gluten-containing diet (SANGUT study): a 12-week, randomized, double-blind, and placebo-controlled clinical study protocol

BACKGROUND

Current treatment of major depressive disorder (MDD) often does not achieve full remission of symptoms. Therefore, new forms of treatment and/or adjunct therapy are needed. Evidence has confirmed the modulation of the gut-brain-microbiota axis as a promising approach in MDD patients. The overall purpose of the SANGUT study-a 12-week, randomized, double-blind, and placebo-controlled Study Evaluating the Effect of Probiotic Supplementation on the Mental Status, Inflammation, and Intestinal Barrier in Major Depressive Disorder Patients Using Gluten-free or Gluten-containing Diet - is to determine the effect of interventions focused on the gut-brain-microbiota axis in a group of MDD patients.

METHODS

A total of 120 outpatients will be equally allocated into one of four groups: (1) probiotic supplementation+gluten-free diet group (PRO-GFD), (2) placebo supplementation+ gluten-free diet group (PLA-GFD), (3) probiotic supplementation+ gluten containing diet group (PRO-GD), and (4) placebo supplementation+gluten containing diet group (PLA-GD). PRO groups will receive a mixture of psychobiotics (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175), and GFD groups will follow a gluten-free diet. The intervention will last 12 weeks. The primary outcome measure is change in wellbeing, whereas the secondary outcome measures include physiological parameters.

DISCUSSION

Microbiota and its metabolites have the potential to influence CNS function. Probiotics may restore the eubiosis within the gut while a gluten-free diet, via changes in the microbiota profile and modulation of intestinal permeability, may alter the activity of microbiota-gut-brain axis previously found to be associated with the pathophysiology of depression. It is also noteworthy that microbiota being able to digest gluten may play a role in formation of peptides with different immunogenic capacities. Thus, the combination of a gluten-free diet and probiotic supplementation may inhibit the immune-inflammatory cascade in MDD course and improve both psychiatric and gut barrier-associated traits.

TRIAL REGISTRATION

NCT03877393 .

Gut Microbial Dysbiosis in the Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis of Case-Control Studies

BACKGROUND

Irritable bowel syndrome (IBS) is the most common functional digestive condition in the industrialized world. The gut microbiota plays a key role in disease pathogenesis.

OBJECTIVE

A systematic review and meta-analysis on case-control studies was conducted to determine whether there is gut microbial dysbiosis in participants with IBS in comparison with healthy controls and, if so, whether the dysbiosis pattern differs among IBS subtypes and geographic regions.

METHODS

This review was conducted and reported according to the MOOSE (Meta-Analysis of Observational Studies in Epidemiology) 2000 and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2009 guidelines. Research articles published up to May 9, 2018 were identified through MEDLINE (PubMed), Cochrane Central Register of Controlled Trials (Cochrane Library), ClinicalTrials.gov, EMBASE, and Web of Science. Study quality was assessed using the Newcastle-Ottawa Scale. Case-control studies of participants with IBS who had undergone quantitative gut microbial stool analysis were included. The primary exposure measure of interest is log₁₀ bacterial counts per gram of stool. Meta-analyses were performed to estimate the mean difference (MD) in gut microbiota between participants with IBS and healthy controls using the random-effects model with inverse variance in Revman 5.3 and R 3.5.1. Publication bias was assessed with funnel plots and Egger's test. Between-study heterogeneity was analyzed using Higgins I² statistic with 95% CIs.

RESULTS

There were 6,333 unique articles identified; 52 qualified for full-text screening. Of these, 23 studies were included for analysis (n=1,340 participants from North America, Europe, and Asia). Overall, the studies were moderate in quality. Comparing participants with IBS to healthy controls, lower fecal Lactobacillus (MD= -0.57 log₁₀ colony-forming unit [CFU]/g; P<0.01) and Bifidobacterium (MD= -1.04 log₁₀CFU/g; P<0.01), higher Escherichia coli (MD=0.60 log₁₀CFU/g; P<0.01), and marginally higher Enterobacter (MD=0.74 log₁₀CFU/g; P=0.05). No difference was found between participants with IBS and healthy controls in fecal Bacteroides and Enterococcus (P=0.18 and 0.68, respectively). Publication bias was not observed except in Bifidobacterium (P=0.015). Subgroup analyses on participants with diarrhea-predominant and constipation-predominant IBS showed consistent results with the primary results. A subgroup analysis of Chinese studies was consistent with the primary results, except for fecal Bacteroides, which was increased in participants with IBS vs healthy controls (MD=0.29; 95% CI 0.13 to 0.46; P<0.01). Although substantial heterogeneity was detected (I²>75%) in most comparisons, the direction of the effect estimates is relatively consistent across studies.

CONCLUSIONS

IBS is characterized by gut microbial dysbiosis. Prospective, large-scale studies are needed to delineate how gut microbial profiles can be used to guide targeted therapies in this challenging patient population.

Effect of mild moxibustion on intestinal microbiota and NLRP6 inflammasome signaling in rats with post-inflammatory irritable bowel syndrome

BACKGROUND

About one-third of refractory irritable bowel syndrome (IBS) cases are caused by gastrointestinal (GI) infection/inflammation, known as post-infectious/post-inflammatory IBS (PI-IBS). Although it is known that intestinal microbiota and host NOD-like receptor family pyrin domain containing 6 (NLRP6) inflammsome signaling are closely related to PI-IBS and moxibustion has a therapeutic effect on PI-IBS, whether moxibustion regulates the intestinal flora and host NLRP6 events in PI-IBS remains unclear.

AIM

To examine the regulatory effect of moxibustion on intestinal microbiota and host NLRP6 inflammatory signaling in PI-IBS.

METHODS

Sprague-Dawley rats were divided into a normal control group, a model control group, a mild moxibustion group, and a sham mild moxibustion group. PI-IBS rats in the mild moxibustion group were treated with moxibusiton at bilateral Tianshu (ST 25) and Zusanli (ST36) for 7 consecutive days for 10 min each time. The sham group rats were given the same treatment as the mild moxibustion group except the moxa stick was not ignited. Abdominal withdrawal reflex (AWR) score was measured to assess the visceral sensitivity, and colon histopathology and ultrastructure, colonic myeloperoxidase (MPO) activity, and serum C-reactive protein (CRP) level were measured to evaluate low-grade colonic inflammation in rats. The relative abundance of selected intestinal bacteria in rat feces was detected by 16S rDNA PCR and the NLRP6 inflammsome signaling in the colon was detected by immunofluorescence, qRT-PCR, and Western blot.

RESULTS

The AWR score was significantly decreased and the low-grade intestinal inflammation reflected by serum CRP and colonic MPO levels was inhibited in the mild moxibustion group compared with the sham group. Mild moxibustion remarkably increased the relative DNA abundances of Lactobacillus, Bifidobacterium, and Faecalibacterium prausnitzii but decreased that of Escherichia coli in the gut of PI-IBS rats. Additionally, mild moxibustion induced mRNA and protein expression of intestine lectin 1 but inhibited the expression of IL-1β, IL-18, and resistance-like molecule β by promoting the NLRP6 and reducing the mRNA and protein expression of apoptosis-associated speck-like protein containing CARD (ASC) and cysteinyl-aspartate-specific proteinase 1 (Caspase-1). The relative DNA abundances of Lactobacillus, Bifidobacteria, Faecalibacterium prausnitzii, and Escherichia coli in each group were correlated with the mRNA and protein expression of NLRP6, ASC, and Caspase-1 in the colon.

CONCLUSION

These findings indicated that mild moxibustion can relieve low-grade GI inflammation and alleviate visceral hypersensitivity in PI-IBS by regulating intestinal microbes and controlling NLRP6 inflammasome signaling.

Systematic review with meta-analysis: efficacy of faecal microbiota transplantation for the treatment of irritable bowel syndrome

BACKGROUND

Increasing evidence supports the role of the gut microbiota in the aetiology of irritable bowel syndrome (IBS). Faecal microbiota transplantation (FMT) is a highly effective treatment against recurrent Clostridioides difficile infection in randomised controlled trials (RCTs), and may be beneficial in ulcerative colitis. However, its efficacy in IBS is uncertain.

AIM

To perform a systematic review and meta-analysis to examine this issue.

METHODS

We searched MEDLINE, EMBASE, EMBASE Classic, the Cochrane Central Register of Controlled Trials, and clinicaltrials.gov through to March 2019. RCTs recruiting adults with IBS, which compared FMT with placebo, were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% CI.

RESULTS

The search strategy identified 322 citations. Five RCTs were eligible for inclusion, containing 267 patients. Overall, 92.2% of included patients had IBS-D or IBS-M, and only 7.8% IBS-C. When data were pooled for all patients, irrespective of stool type, the RR of IBS symptoms not improving was 0.98 (95% CI 0.58-1.66). Placebo capsules administered orally were superior to capsules containing donor stool in two pooled trials (RR = 1.96; 95% CI 1.19-3.20). FMT from donor stool delivered via colonoscopy was superior to autologous stool in two pooled RCTs (RR = 0.63; 95% CI 0.43-0.93). FMT from donor stool via nasojejunal tube showed a trend towards a benefit over autologous stool in one trial (RR = 0.69; 95% CI 0.46-1.02).

CONCLUSIONS

Fresh or frozen donor stool delivered via colonoscopy or nasojejunal tube may be beneficial in IBS. Larger, more rigorously conducted trials of FMT in IBS are needed.

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.

The Microbiome and Irritable Bowel Syndrome - A Review on the Pathophysiology, Current Research and Future Therapy

Irritable bowel syndrome (IBS) is a functional disorder which affects a large proportion of the population globally. The precise etiology of IBS is still unknown, although consensus understanding proposes IBS to be of multifactorial origin with yet undefined subtypes. Genetic and epigenetic factors, stress-related nervous and endocrine systems, immune dysregulation and the brain-gut axis seem to be contributing factors that predispose individuals to IBS. In addition to food hypersensitivity, toxins and adverse life events, chronic infections and dysbiotic gut microbiota have been suggested to trigger IBS symptoms in tandem with the predisposing factors. This review will summarize the pathophysiology of IBS and the role of gut microbiota in relation to IBS. Current methodologies for microbiome studies in IBS such as genome sequencing, metagenomics, culturomics and animal models will be discussed. The myriad of therapy options such as immunoglobulins (immune-based therapy), probiotics and prebiotics, dietary modifications including FODMAP restriction diet and gluten-free diet, as well as fecal transplantation will be reviewed. Finally this review will highlight future directions in IBS therapy research, including identification of new molecular targets, application of 3-D gut model, gut-on-a-chip and personalized therapy.

Can Gut Microbiota Composition Predict Response to Dietary Treatments?

Dietary intervention is a challenge in clinical practice because of inter-individual variability in clinical response. Gut microbiota is mechanistically relevant for a number of disease states and consequently has been incorporated as a key variable in personalised nutrition models within the research context. This paper aims to review the evidence related to the predictive capacity of baseline microbiota for clinical response to dietary intervention in two specific health conditions, namely, obesity and irritable bowel syndrome (IBS). Clinical trials and larger predictive modelling studies were identified and critically evaluated. The findings reveal inconsistent evidence to support baseline microbiota as an accurate predictor of weight loss or glycaemic response in obesity, or as a predictor of symptom improvement in irritable bowel syndrome, in dietary intervention trials. Despite advancement in quantification methodologies, research in this area remains challenging and larger scale studies are needed until personalised nutrition is realistically achievable and can be translated to clinical practice.

How Microbes Shape Their Communities? A Microbial Community Model Based on Functional Genes

Exploring the mechanisms of maintaining microbial community structure is important to understand biofilm development or microbiota dysbiosis. In this paper, we propose a functional gene-based composition prediction (FCP) model to predict the population structure composition within a microbial community. The model predicts the community composition well in both a low-complexity community as acid mine drainage (AMD) microbiota, and a complex community as human gut microbiota. Furthermore, we define community structure shaping (CSS) genes as functional genes crucial for shaping the microbial community. We have identified CSS genes in AMD and human gut microbiota samples with FCP model and find that CSS genes change with the conditions. Compared to essential genes for microbes, CSS genes are significantly enriched in the genes involved in mobile genetic elements, cell motility, and defense mechanisms, indicating that the functions of CSS genes are focused on communication and strategies in response to the environment factors. We further find that it is the minority, rather than the majority, which contributes to maintaining community structure. Compared to health control samples, we find that some functional genes associated with metabolism of amino acids, nucleotides, and lipopolysaccharide are more likely to be CSS genes in the disease group. CSS genes may help us to understand critical cellular processes and be useful in seeking addable gene circuitries to maintain artificial self-sustainable communities. Our study suggests that functional genes are important to the assembly of microbial communities.

Mapping the microbial interactome: Statistical and experimental approaches for microbiome network inference

IMPACT STATEMENT

This review provides a comprehensive description of experimental and statistical tools used for network analyses of the human gut microbiome. Understanding the system dynamics of microbial interactions may lead to the improvement of therapeutic approaches for managing microbiome-associated diseases. Microbiome network inference tools have been developed and applied to both cross-sectional and longitudinal experimental designs, as well as to multi-omic datasets, with the goal of untangling the complex web of microbe-host, microbe-environmental, and metabolism-mediated microbial interactions. The characterization of these interaction networks may lead to a better understanding of the systems dynamics of the human gut microbiome, augmenting our knowledge of the microbiome's role in human health, and guiding the optimization of effective, precise, and rational therapeutic strategies for managing microbiome-associated disease.

Irritable Bowel Syndrome in Terms of Changes in the Microbiota

Aim:to review available data confirming the pathogenetic role of the intestinal microbiota in the formation of irritable bowel syndrome (IBS).

Key findings.Changes in the intestinal biotope cause the development of visceral hypersensitivity and impaired intestinal motor activity, as well as neuroimmune transmission. This article discusses the main aspects of the biological properties of probiotic bacteria in terms of their action within the “brain — intestine — microbiota” chain. The results of experimental and clinical studies elucidating the mechanisms of action of probiotic cultures have been generalized. The understanding of these mechanisms allows practitioners to make informed decisions in prescribing probiotics to IBS patients. Key concepts concerning fecal microbiota transplantation, as well as the prospects and difficulties of implementing this approach are considered.

Conclusions.The term “microbiota — intestine — brain” clearly demonstrates the correlation between the main functional components of IBS. Meta-analyses and systematic reviews confirm the efficacy of probiotics in IBS. However, further research into probiotic therapy options is needed to identify specific bacterial strains with proven clinical efficacy. The fecal microbiota transplantation method also requires further research, since many issues associated with this approach remain unclear.

The dynamics of the antibiotic resistome in the feces of freshly weaned pigs following therapeutic administration of oxytetracycline

In this study, shotgun metagenomics was employed to monitor the effect of oxytetracycline, administered at a therapeutic dose, on the dynamics of the microbiota and resistome in the feces of weaned pigs. Sixteen weaning pigs were assigned to one of two treatments including standard starter diet for 21 days or antibiotic-supplemented diet (10 g oxytetracycline/100 kg body weight/day) for 7 days, followed by 14 days of standard starter diet. Feces were collected from the pigs on days 0, 8, and 21 for microbiota and resistome profiling. Pigs receiving oxytetracycline exhibited a significantly greater richness (ANOVA, P = 0.034) and diversity (ANOVA, P = 0.048) of antibiotic resistance genes (ARGs) than the control pigs. Antibiotic administration significantly enriched the abundances of 41 ARGs, mainly from the tetracycline, betalactam and multidrug resistance classes. Compositional shifts in the bacterial communities were observed following 7 days of antibiotic adminstration, with the medicated pigs showing an increase in Escherichia (Proteobacteria) and Prevotella (Bacteroidetes) populations compared with the nonmedicated pigs. This might be explained by the potential of these taxa to carry ARGs that may be transferred to other susceptible bacteria in the densely populated gut environment. These findings will help in the optimization of therapeutic schemes involving antibiotic usage in swine production.

Intestinal Microbiota in Early Life and Its Implications on Childhood Health

Trillions of microbes reside in the human body and participate in multiple physiological and pathophysiological processes that affect host health throughout the life cycle. The microbiome is hallmarked by distinctive compositional and functional features across different life periods. Accumulating evidence has shown that microbes residing in the human body may play fundamental roles in infant development and the maturation of the immune system. Gut microbes are thought to be essential for the facilitation of infantile and childhood development and immunity by assisting in breaking down food substances to liberate nutrients, protecting against pathogens, stimulating or modulating the immune system, and exerting control over the hypothalamic-pituitary-adrenal axis. This review aims to summarize the current understanding of the colonization and development of the gut microbiota in early life, highlighting the recent findings regarding the role of intestinal microbes in pediatric diseases. Furthermore, we also discuss the microbiota-mediated therapeutics that can reconfigure bacterial communities to treat dysbiosis.

The role of a sequencing-based clinical intestinal screening test in patients at high-risk for Clostridium difficile and other pathogens: a case report

BACKGROUND

Hospitalization and antibiotic treatment can put patients at high risk for Clostridium difficile infection, where a disturbance of the gut microbiome allows for Clostridium difficile proliferation and associated symptoms, including mild, moderate, or severe diarrhea. Clostridium difficile infection is challenging to treat, often recurrent, and leads to almost 30,000 annual deaths in the USA alone. Here we present a case where SmartGut™, an at-home, self-administered sequencing-based clinical intestinal screening test, was used to identify the presence of Clostridium difficile in a patient with worsening diarrhea. Identification of this pathogen and subsequent treatment led to a significant improvement in symptoms.

CASE PRESENTATION

The patient is a 29-year-old white woman with a history of severe irritable bowel syndrome with diarrhea, hemorrhoidectomy, and anal sphincterotomy complicated by a perianal fistula and perirectal abscesses that required extended courses of broad-spectrum antibiotics. In June 2016, she developed intermittent Clostridium difficile infections, which required continued antibiotic use. Months later she used an at-home, self-administered, intestinal microbial test, the first of which was negative for the presence of Clostridium difficile, but it detected the relative abundance of microbes associated with irritable bowel syndrome outside the healthy reference ranges. In the subsequent 2 months after the negative Clostridium difficile result, her gastrointestinal symptoms worsened dramatically. A second microbiome test resulted in a positive Clostridium difficile finding and continued abnormal microbial parameters, which led the treating physician to refer her to a gastroenterologist. Additional testing confirmed the presence of Clostridium difficile with a toxin-positive strain. She received treatment immediately and her gastrointestinal symptoms improved significantly over the next week.

CONCLUSIONS

This case report suggests that more frequent DNA testing for Clostridium difficile infections may be indicated in patients that are at high-risk for Clostridium difficile infection, especially for patients with irritable bowel syndrome, and those who undergo gastrointestinal surgery and/or an extended antibiotic treatment. This report also shows that such testing could be effectively performed using at-home, self-administered sequencing-based clinical intestinal microbial screening tests. Further research is needed to investigate whether the observations reported here extrapolate to a larger cohort of patients.

Rome Foundation Working Team Report on Post-Infection Irritable Bowel Syndrome

BACKGROUND & AIMS

The existence of postinfection irritable bowel syndrome (PI-IBS) has been substantiated by epidemiology studies conducted in diverse geographic and clinical settings. However, the available evidence has not been well summarized, and there is little guidance for diagnosis and treatment of PI-IBS. The ROME Foundation has produced a working team report to summarize the available evidence on the pathophysiology of PI-IBS and provide guidance for diagnosis and treatment, based on findings reported in the literature and clinical experience.

METHODS

The working team conducted an evidence-based review of publication databases for articles describing the clinical features (diagnosis), pathophysiology (intestinal sensorimotor function, microbiota, immune dysregulation, barrier dysfunction, enteroendocrine pathways, and genetics), and animal models of PI-IBS. We used a Delphi-based consensus system to create guidelines for management of PI-IBS and a developed treatment algorithm based on published findings and experiences of team members.

RESULTS

PI-IBS develops in about 10% of patients with infectious enteritis. Risk factors include female sex, younger age, psychological distress during or before acute gastroenteritis, and severity of the acute episode. The pathogenesis of PI-PBS appears to involve changes in the intestinal microbiome as well as epithelial, serotonergic, and immune system factors. However, these mechanisms are incompletely understood. There are no evidence-based, effective pharmacologic strategies for treatment of PI-IBS. We provide a consensus-based treatment algorithm, based on clinical presentation and potential disease mechanisms.

CONCLUSIONS

Based on a systematic review of the literature and team experience, we summarize the clinical features, pathophysiology (from animal models and human studies), and progression of PI-IBS. Based on these findings, we present an algorithm for diagnosis and treatment of PI-IBS based on team consensus. We also propose areas for future investigation.

Montezuma’s revenge - the sequel: The one-hundred year anniversary of the first description of “post-infectious” irritable bowel syndrome

One-hundred years have passed since the original description of the commonly described phenomenon of persistent abdominal symptoms being triggered by an acute enteric infection. This first account was generated out of astute observations by Sir Arthur Hurst in World War I. Additional descriptions followed from military and non-military practitioners adding the evidence which has transitioned this recognized condition from association to causation. While mechanistic understanding is an area of active pursuit, this historical accounting of a centuries progress highlights important advances and contributions of military medicine and scientists to advances benefiting global populations.

The kinetics of gut microbial community composition in patients with irritable bowel syndrome following fecal microbiota transplantation

Background

Gut microbiota alterations are important in irritable bowel syndrome (IBS). The aim was to investigate the effect of fecal microbiota transplantation (FMT) on gut microbiota and the symptoms in patients with IBS.

Material and methods

The study included 13 IBS patients according to Rome III criteria and 13 healthy donors. Freshly donated feces were administered to the descending part of the duodenum via a gastroscope. Feces were collected from donors and patients before FMT, and from the patients at 1, 3 and 12 weeks and donors and patients at 20/28 weeks after FMT. Microbiota analysis was performed using GA-map Dysbiosis test (Genetic Analysis AS, Oslo, Norway). The patients completed the following questionnaires before and at the aforementioned weeks after FMT: IBS Symptom Questionnaire (IBS-SQ), IBS-Symptom Severity Scoring system (IBS-SSS), Short Form of Nepean Dyspepsia Index (SF-NDI), Bristol stool form scale, the Eysenck Personality Questionnaire-Neuroticism and Hospital Anxiety and Depression.

Results

Donors and IBS patients had significantly different bacterial strain signals before FMT (Ruminococcus gnavus, Actinobacteria and Bifidobacteria) that became non-significant after 3 weeks following FMT. The changes in gut microbiota were similar between donors and patients at 20/28 weeks after FMT. Thus, patients’ microbiota profiles became more-or-less similar to donors.

The scores of all the questionnaires were significantly improved at all time points following FMT. No reported adverse effects.

Conclusions

FMT was associated with a change in gut microbiota and improvement in IBS symptoms and quality of life lasting for up to 28 weeks.

Trial registration

ClinicalTrials.gov ID:NCT03333291

Fecal chromogranins and secretogranins are linked to the fecal and mucosal intestinal bacterial composition of IBS patients and healthy subjects

Altered fecal levels of chromogranins (Cg) and secretogranins (Sg) are demonstrated in irritable bowel syndrome (IBS), but their role in IBS pathophysiology remains unknown. This study aimed to determine if granins are associated with bacterial composition, immune activation and IBS symptoms. Protein levels of fecal granins (CgA, CgB, SgII and SgIII) were analysed with immunoassays. Mucosal mRNA expression of granins, TPH1 and immune markers were evaluated with RT-qPCR. 16S rRNA gene sequencing was performed on fecal and mucosal bacteria. The intestinal granin profile, based on fecal protein levels and mucosal mRNA expression, could not discriminate between IBS patients (n = 88) and healthy subjects (HS, n = 33). IBS patients dominated by high fecal or mucosal granin levels, respectively, did not differ in symptom or immune profiles. Fecal-dominated and mucosal-dominated granin clusters of IBS patients and HS, demonstrated separate fecal and mucosal bacterial profiles and high fecal abundance of granins were associated with a less diverse bacterial composition and the Bacteroides enterotype. The intestinal granin profiles of IBS patients and HS are linked to the intestinal bacterial composition, diversity and enterotypes. These findings suggest that granins may be one of several host-produced factors regulating the microbiota composition of the intestine.

A four-strain probiotic exerts positive immunomodulatory effects by enhancing colonic butyrate production in vitro

Poorly formulated probiotic supplements intended for oral administration often fail to protect bacteria from the challenges of human digestion, meaning bacteria do not reach the small intestine in a viable state. As a result, the ability of probiotics to influence the human gut microbiota has not been proven. Here we show how (i) considered formulation of an aqueous probiotic suspension can facilitate delivery of viable probiotic bacteria to the gut and (ii) quantitate the effect of colonisation and proliferation of specific probiotic species on the human gut microbiota, using an in-vitro gut model. Our data revealed immediate colonisation and growth of three probiotic species in the luminal and mucosal compartments of the proximal and distal colon, and growth of a fourth species in the luminal proximal colon, leading to higher proximal and distal colonic lactate concentrations. The lactate stimulated growth of lactate-consuming bacteria, altering the bacterial diversity of the microbiota and resulting in increased short-chain fatty acid production, especially butyrate. Additionally, an immunomodulatory effect of the probiotics was seen; production of anti-inflammatory cytokines (IL-6 and IL-10) was increased and production of inflammatory chemokines (MCP-1, CXCL 10 and IL-8.) was reduced. The results indicate that the probiotic species alone do not result in a clinical effect; rather, they facilitate modulation of the gut microbiota composition and metabolic activity thereby influencing the immune response.

Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic functional bowel disorder. Disturbances in the gastrointestinal microbiome may be involved in its aetiology.

AIM

To perform a systematic review and meta-analysis to examine the efficacy of prebiotics, probiotics, synbiotics and antibiotics in IBS.

METHODS

MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to July 2017). Randomised controlled trials (RCTs) recruiting adults with IBS, comparing prebiotics, probiotics, synbiotics or antibiotics with placebo or no therapy were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). Continuous data were pooled using a standardised mean difference with a 95% CI.

RESULTS

The search identified 4017 citations. Data for prebiotics and synbiotics were sparse. Fifty-three RCTs of probiotics, involving 5545 patients, were eligible. Particular combinations of probiotics, or specific species and strains, appeared to have beneficial effects on global IBS symptoms and abdominal pain, but it was not possible to draw definitive conclusions about their efficacy. There were five trials of similar design that used rifaximin in non-constipated IBS patients, which was more effective than placebo (RR of symptoms persisting = 0.84; 95% CI 0.79-0.90). Adverse events were no more common with probiotics or antibiotics.

CONCLUSIONS

Which particular combination, species or strains of probiotics are effective for IBS remains, for the most part, unclear. Rifaximin has modest efficacy in improving symptoms in non-constipated IBS.

A Microbial Signature of Psychological Distress in Irritable Bowel Syndrome

OBJECTIVE

Irritable bowel syndrome (IBS) is associated with alterations along the brain-gut-microbiota axis. Previous studies have suggested a parallel segregation of microbial features and psychological burden in IBS. This study aimed at exploring the microbial correlates of psychological distress in patients with IBS.

METHODS

Forty-eight patients with IBS (Rome III criteria, M (SD) age = 42 (15) years, 35 female, 25 diarrhea-dominant, 5 constipation-dominant, and 18 alternating-type IBS) were assessed for psychological and clinical variables with validated questionnaires, fecal samples underwent microbial 16S rRNA analyses (regions V1-2). Microbial analyses comprised examination of alpha and beta diversity, correlational analyses of bacterial abundance and comparisons among subgroups defined by thresholds of psychological and IBS symptom variables, and machine learning to identify bacterial patterns corresponding with psychological distress.

RESULTS

Thirty-one patients (65%) showed elevated psychological distress, 22 (31%) anxiety, and 10 depression (21%). Microbial beta diversity was significantly associated with distress and depression (q = .036 each, q values are p values false discovery rate-corrected for multiple testing). Depression was negatively associated with Lachnospiraceae abundance (Spearman's ρ = -0.58, q = .018). Patients exceeding thresholds of distress, anxiety, depression, and stress perception showed significantly higher abundances of Proteobacteria (q = .020-.036). Patients with anxiety were characterized by elevated Bacteroidaceae (q = .036). A signature of 148 unclassified species accounting for 3.9% of total bacterial abundance co-varied systematically with the presence of psychological distress.

CONCLUSIONS

Psychological variables significantly segregated gut microbial features, underscoring the role of brain-gut-microbiota interaction in IBS. A microbial signature corresponding with psychological distress was identified.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT02536131, retrospectively registered.

New treatments and therapeutic targets for IBS and other functional bowel disorders

Functional bowel disorders (FBDs) are a spectrum of disorders characterized by combinations of symptoms attributable to the lower gastrointestinal tract. Most current first-line therapies for IBS and other FBDs target the predominant symptom and mainly affect one symptom in the symptom complex. Additional broadly effective treatment alternatives targeting the entire symptom complex are needed. New drugs for FBDs (such as lubiprostone, linaclotide, plecanatide, prucalopride, eluxadoline and rifaximin) target key mechanisms in the pathophysiology of these disorders and improve both the abnormal bowel habit and other key symptoms, such as abdominal pain and bloating. The current development of new treatment alternatives is focusing on different aspects of the complex pathophysiology of IBS and other FBDs: gut microenvironment (via diet and modulation of gut microbiota), enterohepatic circulation of bile acids, gastrointestinal secretion, motility and sensation, gut-brain interactions, gut barrier function and the immune system within the gastrointestinal tract. Studies also suggest that personalized treatment of IBS and other FBDs is possible using various diagnostic markers.

A Meta-Analysis of the Clinical Use of Curcumin for Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) remains a prevalent and difficult-to-manage gastrointestinal condition. There is growing interest in the use of traditional medicine to manage IBS. In particular, curcumin, a biologically active phytochemical, has demonstrated anti-inflammatory and anti-oxidant properties and mucosal protective effects in rat models of colitis. This meta-analysis thus aimed to investigate the hypothesis that curcumin improves IBS symptoms. Using the keywords (curcumin OR turmeric OR Indian saffron OR diferuloylmethane OR curcuminoid) AND (irritable bowel syndrome OR IBS), a preliminary search on the PubMed, Medline, Embase, PsychINFO, Web of Science, and Google Scholar databases yielded 1080 papers published in English between 1 January 1988 and 1 May 2018. Five randomized, controlled trials were systematically reviewed and 3 were included in the final meta-analysis. Random-effects meta-analysis based on three studies and 326 patients found curcumin to have a beneficial albeit not statistically significant effect on IBS symptoms (pooled standardized mean difference from baseline IBS severity rating -0.466, 95% CI: -1.113 to 0.182, p = 0.158). This is the first meta-analysis to examine the use of curcumin in IBS. With its unique anti-oxidant and anti-inflammatory activities and ability to modulate gut microbiota, curcumin is a potentially useful addition to our armamentarium of agents for IBS. It also appears safe and well-tolerated, with no adverse events reported in the available trials. However, current findings are based on a considerably limited evidence base with marked heterogeneity. More robust clinical trials involving a standardized curcumin preparation and larger sample sizes should be encouraged.

The role of inflammation in irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a complex, functional gastrointestinal disorder characterized by chronic abdominal pain or discomfort and altered bowel habits. Despite the global prevalence and disease burden of IBS, its underlying pathophysiology remains unclear. Inflammation may play a pathogenic role in IBS. Studies have highlighted the persistence of mucosal inflammation at the microscopic and molecular level in IBS, with increased recruitment of enteroendocrine cells. Substantial overlaps between IBS and inflammatory bowel disease have also been reported. This review thus aimed to discuss the body of evidence pertaining to the presence of mucosal inflammation in IBS, its putative role in the disease process of IBS, and its clinical relevance. Increased mast cell density and activity in the gut may correlate with symptoms of visceral hypersensitivity. As evidenced by patients who develop postinfectious IBS, infective gastroenteritis could cause systemic inflammation and altered microbiome diversity, which in turn perpetuates a cycle of chronic, low-grade, subclinical inflammation. Apart from mucosal inflammation, neuroinflammation is probably involved in the pathophysiology of IBS via the "gut-brain" axis, resulting in altered neuroendocrine pathways and glucocorticoid receptor genes. This gives rise to an overall proinflammatory phenotype and dysregulated hypothalamic-pituitary-adrenal axis and serotonergic (5-HT) functioning, which could, at least in part, account for the symptoms of IBS. Although a definite and reproducible pattern of immune response has yet to be recognized, further research into anti-inflammatories may be of clinical value.

Effect of probiotic Bifidobacterium bifidum G9-1 on the relationship between gut microbiota profile and stress sensitivity in maternally separated rats

Although gut microbiota and early life events are likely involved in the development of irritable bowel syndrome (IBS), it remains unclear how these factors interact in the pathophysiology of IBS. In the present study, using rats subjected to maternal separation (MS) as a model of IBS, we investigated interrelationships among gut microbiota, stress susceptibility and intestinal permeability, and examined the effect of the probiotic Bifidobacterium bifidum G9-1 (BBG9-1) on those interrelationships. When compared with the controls at postnatal day 20, MS rats showed hypercorticosteronemia, enhanced intestinal permeability and changes in gut microbiota structure. All of these changes in MS rats were prevented by treatment with BBG9-1. Although the gut microbiota profile and basal serum corticosterone level did not differ between MS and control rats at postnatal day 56, MS rats showed hypersensitivity to restraint stress in terms of serum corticosterone level and fecal frequency. However, such hypersensitivity was not observed in MS rats treated with BBG9-1. These findings suggest that MS initiates the link between gut microbiota alteration and hypersensitivity to stress and that the triggering of this process can be prevented by the treatment with the probiotic BBG9-1.

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.

Fecal Microbiota Alterations Associated With Diarrhea-Predominant Irritable Bowel Syndrome

Altered gut microbiota are assumed to be involved in the pathogenesis of irritable bowel syndrome (IBS). However, gut microbiota alterations reported in different studies are divergent and sometimes even contradictory. To better elucidate the relationship between altered gut microbiota and IBS, we characterized fecal microbiota of diarrhea-predominant IBS (IBS-D) patients and further explored the effect of rifaximin on gut microbiota using bacterial 16S rRNA gene-targeted pyrosequencing. In our study, IBS-D patients defined by Rome III criteria and age-and-gender matched healthy controls (HC) were enrolled to investigate the fecal microbiota alterations. These IBS-D patients were then treated with rifaximin for 2 weeks and followed up for 10 weeks. Fecal microbiota alterations, small intestine bacterial overgrowth (SIBO) and gastrointestinal (GI) symptoms of IBS-D patients were analyzed before and after treatment. Our results showed fecal microbiota richness but not diversity was decreased in IBS-D patients as compared to HC and there were alterations of fecal microbiota at different taxonomy levels. The abundant phyla Firmicutes was significantly decreased and Bacteroidetes was increased in IBS-D patients. Moreover, the alterations of predominant fermenting bacteria such as Bacteroidales and Clostridiales might be involved in the pathophysiology of IBS-D. In addition, rifaximin was effective in terms of SIBO eradication and even GI symptoms of IBS-D patients achieved at least 10-week improvement after treatment. Furthermore, rifaximin induced alterations of some special bacteria rather than affected the overall composition of microbiota in IBS-D patients. Meanwhile, a potential decrease in propanoate and butanoate metabolism was found in these IBS-D patients after rifaximin treatment. Taken together, there were alterations of gut microbiota in IBS-D patients as compared to HC. Rifaximin could relieve GI symptoms, modify gut microbiota in IBS-D patients and eradicate SIBO in those patients with SIBO, suggesting an additional therapeutic mechanism of rifaximin in the treatment of IBS-D. Our findings of compositional gut microbiota alterations in IBS-D and the effect of rifaximin on the gut microbiota implied that altered gut microbiota were associated with the pathogenesis of IBS.

Idiopathic Colitis in Rhesus Macaques Is Associated With Dysbiosis, Abundant Enterochromaffin Cells and Altered T-Cell Cytokine Expression

Idiopathic chronic diarrhea (ICD) is a common ailment affecting captive rhesus macaques ( Macaca mulatta). ICD cases are characterized by diarrhea in the absence of commonly identified diarrheal pathogens and multiple recurrences even after supportive therapy. Histologically, the disease is characterized by lymphoplasmacytic colitis. We identified 35 rhesus macaques euthanized for ICD during a 7-month period and described demographic, clinical, histologic, and immunologic commonalities. We found a trend of historic Campylobacter spp. and trichomonad infections. Furthermore, rhesus macaques with ICD demonstrated loss of normal colonic adherent bacterium, identified in this study as Helicobacter macacae; increased abundance of Pentatrichomonas hominis; and increased frequency of colonic serotonin-positive enterochromaffin cells. Interestingly, colonic and ileal T-helper cells of animals with ICD manifested decreased capacity for expression of certain cytokines, in particular interleukin (IL)-4 and IL-13. These data further describe a common ailment and suggest new avenues to identify complex interactions involved in the etiology of recurring diarrhea in young rhesus macaques.

The gut microbiome and irritable bowel syndrome: State of art review

Irritable bowel syndrome (IBS) is a functional disorder of the gastrointestinal tract, the physiology of which is not very well understood. There are multiple factors and pathways involved in pathogenesis of this entity. Among all, dysmotility, dysregulation of the brain-gut axis, altered intestinal microbiota and visceral hypersensitivity play a major role. Over the last years, research has shown that the type of gut microbiome present in an individual plays a significant role in the pathophysiology of IBS. Multiple studies have consistently shown that subjects diagnosed with IBS have disruption in gut microbiota balance. It has been established that host immune system and its interaction with metabolic products of gut microbiota play an important role in the gastrointestinal tract. Therefore, probiotics, prebiotics and antibiotics have shown some promising results in managing IBS symptoms via modulating the interaction between the above. This paper discusses the various factors involved in pathophysiology of IBS, especially gut microbiota.

Characteristics of the bacterial microbiome in association with common intestinal parasites in irritable bowel syndrome

Objective

A low prevalence of intestinal parasites has been identified in individuals with irritable bowel syndrome (IBS), but potential associations with alterations in the bacterial microbiome remain largely unexplored. We aimed to investigate the relationship between parasites and bacteria in individuals with IBS in order to identify potential trans-kingdom microbial characteristics.

Design

Stool samples were collected from the Danish background population classified into IBS (n = 119), unspecific gastrointestinal (GI) symptoms (n = 114), and asymptomatic controls (n = 186) based on the Rome III criteria for IBS. Bacterial (16S) and eukaryotic (18S) ribosomal DNA was sequenced, and 18S data were merged with data from conventional parasite laboratory tests. The bacterial microbiome was analyzed according to symptom group and parasite colonization status.

Results

Bacterial richness and diversity were similar for IBS and controls but higher in those with unspecific GI symptoms. A higher abundance of Bacteroides and a lower abundance of Faecalibacterium were detected in individuals with IBS and unspecific GI symptoms compared with controls. Principal component analyses indicated differences in bacterial composition related to parasite colonization rather than symptom group. Parasites were detected at the lowest frequency in the IBS group (39%) and in samples dominated by Bacteroides. Higher bacterial richness and diversity were found in parasite-positive samples from controls and those with unspecific GI symptoms but not in individuals with IBS.

Conclusion

Parasite colonization, rather than bacterial composition, differed between individuals with IBS and healthy controls. Parasite colonization was associated to a rich and diverse bacterial microbiome; however, this association was altered in IBS.