IBS-associated phylogenetic unbalances of the intestinal microbiota are not reverted by probiotic supplementation

IBS is a prevalent functional gastrointestinal disorder, in which the microbiota has been demonstrated to play a role. An increasing number of studies have suggested how probiotics may alleviate IBS symptoms and several mechanisms of action have been proposed. In the present study we characterized the intestinal microbiota of 19 subjects suffering from diagnosed IBS using a fully validated High Taxonomic Fingerprint Microbiota Array (HTF-Microbi.Array). We demonstrated that the IBS microbiota is different from that of healthy individuals due to an unbalance in a number of commensal species, with an increase in relative abundance of lactobacilli, B. cereus and B. clausii, bifidobacteria, Clostridium cluster IX and E. rectale, and a decrease in abundance of Bacteroides/Prevotella group and Veillonella genus. Additionally, we demonstrated that some bacterial groups of the human intestinal microbiota, recently defined as pathobionts, are increased in concentration in the IBS microbiota. Furthermore, we aimed at investigating if the daily administration of a novel probiotic yogurt containing B. animalis subsp lactis Bb12 and K. marxianus B0399, recently demonstrated to have beneficial effects in the management of IBS symptoms, could impact on the biostructure of IBS microbiota, modulating its composition to counteract putative dysbiosis found in IBS subjects. Notably, we demonstrated that the beneficial effects associated to the probiotic preparation are not related to significant modifications in the composition of the human intestinal microbiota.     

Fecal excretion of Bifidobacterium infantis 35624 and changes in fecal microbiota after eight weeks of oral supplementation with encapsulated probiotic

Certain randomized, placebo-controlled trials of oral supplementation with B. infantis 35624 have demonstrated the amelioration of symptoms of irritable bowel syndrome. Potential GI colonization by B. infantis 35624 or effects of supplementation on resident GI microbiota may pertain to these clinical observations. In this study, fecal excretion of B. infantis 35624 before, during and after 8 weeks of daily treatment was compared in subjects with IBS who received either the encapsulated oral supplement (n = 39) or placebo (n = 37) and in healthy subjects who received the supplement (n = 41). Secondarily, changes in assessed fecal microbiota and IBS symptoms were determined. Supplementation significantly increased fecal B. infantis 35624 excretion vs. placebo in IBS subjects; excretion in healthy subjects receiving supplement was quantitatively similar. Fecal levels of the probiotic declined and approached baseline once dosing ceased, documenting that colonization is transient. Although supplementation increased numbers of B infantis 35624 within the GI tract, limited changes in 10 other fecal taxa were observed either in healthy subjects or those with IBS. No impact on IBS symptoms was observed. Detection of bacterial DNA in fecal samples suggests that the probiotic is able to survive transit through the GI tract, although strain selective culture techniques were not performed to confirm viability of B. infantis 35624 in the feces. Continuous probiotic administration was necessary to maintain steady-state transit. Given the complex spectrum of GI microbiota, however, monitoring perturbations in selected taxa may not be not a useful indicator of probiotic function.     

Effects of probiotic fermented milk on symptoms and intestinal flora in patients with irritable bowel syndrome: A randomized,placebo-controlled trial

Abstract

Objective. The effect of probiotics on IBS symptoms has been mixed, but remains an intriguing treatment option with appeal to the patient. Material and methods. Patients fulfilling the Rome II criteria were randomized double-blind to a daily intake of 500 ml of fermented milk containing at least 5 × 10⁷ CFU/ml of Lactobacillus paracasei ssp paracasei F19, Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12 or an equal volume of acidified milk for 8 weeks. Symptoms were assessed at baseline and weekly using a disease-specific validated symptom rating scale (IBS-SSI). The predefined primary outcome measure was patient reported adequate symptom relief. Adherence to study protocol were assessed by performing stool samples at the of the treatment period. Results. Eight-one patients were screened. Sixty-four patients were randomized; 18 patients did not complete the study due to protocol violations or withdrew due to lack of effect. Fifty-two patients (13 males) completed the study as per protocol; mean age was 51.3 years (range 29–67). The proportion of patients reporting adequate symptom relief increased in both patient groups, but there was not any statistical difference between the groups. IBS-SSI scores did not differ statistically between the groups at the end of the treatment period, but improved during the study period in both groups. Conclusions. During this 8-week trial gastrointestinal symptoms improved. However, there was no difference between treatment with fermented milk containing probiotics or acidified milk. The effect of probiotics on IBS symptoms remains uncertain and further studies are warranted.     

Diagnosis of small intestinal bacterial overgrowth: the challenges persist!

Small intestinal bacterial overgrowth was originally defined in the context of an overt malabsorption syndrome and diagnostic tests were developed and validated accordingly. More recently, the concept of intestinal contamination with excessive numbers of bacteria, especially those of colonic type, has been extended beyond the bounds of frank maldigestion and malabsorption to explain symptomatology in disorders as diverse as irritable bowel syndrome, celiac sprue and nonalcoholic fatty liver disease. Owing to a lack of consensus with regard to the optimal diagnostic criteria (the ‘gold standard’) for the diagnosis of bacterial overgrowth, the status of these new concepts is unclear. This review sets out to critically appraise the various diagnostic approaches that have been taken and are currently employed to diagnose small intestinal bacterial overgrowth.     

Methodological issues in the study of intestinal microbiota in irritable bowel syndrome

Irritable bowel syndrome (IBS) is an intestinal functional disorder with the highest prevalence in the industrialized world. The intestinal microbiota (IM) plays a role in the pathogenesis of IBS and is not merely a consequence of this disorder. Previous research efforts have not revealed unequivocal microbiological signatures of IBS, and the experimental results are contradictory. The experimental methodologies adopted to investigate the complex intestinal ecosystem drastically impact the quality and significance of the results. Therefore, to consider the methodological aspects of the research on IM in IBS, we reviewed 29 relevant original research articles identified through a PubMed search using three combinations of keywords: “irritable bowel syndrome + microflora”, “irritable bowel syndrome + microbiota” and “irritable bowel syndrome + microbiome”. For each study, we reviewed the quality and significance of the scientific evidence obtained with respect to the experimental method adopted. The data obtained from each study were compared with all considered publications to identify potential inconsistencies and explain contradictory results. The analytical revision of the studies referenced in the present review has contributed to the identification of microbial groups whose relative abundance significantly alters IBS, suggesting that these microbial groups could be IM signatures for this syndrome. The identification of microbial biomarkers in the IM can be advantageous for the development of new diagnostic tools and novel therapeutic strategies for the treatment of different subtypes of IBS.     

Impaired transit and tolerance of intestinal gas in the irritable bowel syndrome

BACKGROUND: Patients with irritable bowel syndrome (IBS) frequently complain of excessive gas but their fasting volume of intestinal gas is apparently normal. We hypothesised that the pathophysiological mechanism involved may be impairment of intestinal gas transit. AIM: To investigate intestinal gas transit and tolerance in IBS patients compared with healthy subjects. METHODS: A gas mixture (N(2), O(2), and CO(2) in venous proportions) was infused into the jejunum of 20 patients with IBS and 20 healthy controls at 12 ml/min for four hours. Gas evacuation, initially flatus from the anus (two hours) and then intrarectally (two hours), was continuously recorded. Symptom perception (0-6 scale) and abdominal distension were measured at 10 minute intervals. RESULTS: After two hours of external gas (flatus) collection, 18 of 20 IBS patients had developed gas retention (>400 ml), increased gastrointestinal symptoms (score >3), or abdominal distension (>3 mm girth increment) compared with only four of 20 control subjects. During intrarectal gas collection, 13 of 17 patients still exhibited abnormal responses. CONCLUSION: A large proportion of patients with IBS can be shown to have impaired transit and tolerance of intestinal gas loads. This anomaly may represent a possible mechanism of IBS symptoms, specifically pain and bloating.     

Reduced interstitial cells of Cajal and increased intraepithelial lymphocytes are associated with development of small intestinal bacterial overgrowth in post-infectious IBS mouse model

Objective: Intestinal dysmotility and immune activation are likely involved in the pathogenesis of small intestinal bacteria overgrowth (SIBO) in irritable bowel syndrome (IBS). We aimed at investigating the role of interstitial cells of Cajal (ICC) and intestinal inflammation in the development of SIBO using a post-infectious IBS (PI-IBS) mouse model.

Materials and methods: NIH mice were randomly infected with Trichinella spiralis. Visceral sensitivity and stool pattern were assessed at 8-weeks post-infection (PI). Intestinal bacteria counts from jejunum and ileum were measured by quantitative real-time PCR to evaluate the presence of SIBO. ICC density, intraepithelial lymphocytes (IELs) counts, and intestinal cytokine levels (IL1-β, IL-6, toll-like receptor-4 (TLR-4), IL-10) in the ileum were examined.

Results: PI-IBS mice demonstrated increased visceral sensitivity compared with the control group. One-third of the PI-IBS mice developed SIBO (SIBO+/PI-IBS) and was more likely to have abnormal stool form compared with SIBO negative PI-IBS (SIBO?/PI-IBS) mice but without difference in visceral sensitivity. SIBO+/PI-IBS mice had decreased ICC density and increased IELs counts in the ileum compared with SIBO?/PI-IBS mice. No difference in inflammatory cytokine expression levels were detected among the groups except for increased TLR-4 in PI-IBS mice compared with the control group.

Conclusions: Development of SIBO in PI-IBS mice was associated with reduced ICC density and increased IELs counts in the ileum. Our findings support the role of intestinal dysmotility and inflammation in the pathogenesis of SIBO in IBS and may provide potential therapeutic targets.     

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

ABSTRACT

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

A survey on the developmental intestinal microbiota research in China: The history,funding, and frontiers of gut bacteria

Up to 100 trillion bacteria are harbored in the human intestine with a mutualistic and interdependent relationship with the host during a long period of co‐evolution. The so‐called intestinal microbiota (IM) fulfill important metabolic tasks and the impaired stability may lead to IM‐related diseases, including inflammatory bowel disease (IBD), colorectal cancer (CRC), metabolic syndrome (MS), liver diseases, and so on. Here, we review the past and development of IM research in China, including the achievements that Chinese researchers have made both in basic and clinical scientific field. Moreover, we evaluate the contributions of the National Natural Science Foundation of China (NSFC), the 973 National Basic Research Program of China (973 Program), the 863 National High Technology Research and Development Program of China (863 Program), and funds from the public health industry in the field of IM research.     

Restitution of gut microbiota in Ugandan children administered with probiotics (Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis BB-12) during treatment for severe acute malnutrition

ABSTRACT

Severe acute malnutrition (SAM) is a major challenge in low-income countries and gut microbiota (GM) dysbiosis may play a role in its etiology. Here, we determined the GM evolution during rehabilitation from SAM and the impact of probiotics (Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis BB-12) supplementation. The GM (16S rRNA gene amplicon sequencing) of children admitted to hospital with SAM showed distinct composition over admission (e.g. Klebsiella spp., and Enterobacteriaceae spp.), discharge (e.g. Clostridiaceae spp., Veilonella dispar) and follow-up (e.g. Lactobacillus ruminis, Blautia spp., Faecalibacterium prausnitzii), reaching similar β- and α-diversity as healthy individuals. Children with diarrhea had reduced distribution of Bacteroidaceae, Lachnospiraceae, increased Enterobacteriaceae and Moraxellaceae, and lower α-diversity. Children suffering from edematous SAM had diminished proportion of Prevotellaceae, Lachnospiraceae, Ruminoccaceae and a higher α-diversity when compared to non-edematous SAM. Supplementation of probiotics did not influence β-diversity upon discharge or follow-up, but it increased (p < .05) the number of observed species [SE: > 4.5]. Children where the probiotic species were detected had lower cumulative incidence (p < .001) of diarrhea during the follow-up period compared to children receiving placebo and children receiving probiotics, but where the probiotics were not detected. The GM of children with non-edematous and edematous SAM differ in composition, which might have implications for future GM targeted treatments. Probiotics treatment reduced the cumulative incidence of diarrhea during the outpatient phase, with the strongest effect in children where the administered probiotics could be detected in the GM.     

The gut microbiome stability is altered by probiotic ingestion and improved by the continuous supplementation of galactooligosaccharide

ABSTRACT

The stable gut microbiome plays a key role in sustaining host health, while the instability of gut microbiome also has been found to be a risk factor of various metabolic diseases. At the ecological and evolutionary scales, the inevitable competition between the ingested probiotic and indigenous gut microbiome can lead to an increase in the instability. It remains largely unclear if and how exogenous prebiotic can improve the overall gut microbiome stability in probiotic consumption. In this study, we used Lactobacillus plantarum HNU082 (Lp082) as a model probiotic to examine the impact of the continuous or pulsed supplementation of galactooligosaccharide (GOS) on the gut microbiome stability in mice using shotgun metagenomic sequencing. Only continuous GOS supplement promoted the growth of probiotic and decreased its single-nucleotide polymorphisms (SNPs) mutation under competitive conditions. Besides, persistent GOS supplementation increased the overall stability, reshaped the probiotic competitive interactions with Bacteroides species in the indigenous microbiome, which was also evident by over-abundance of carbohydrate-active enzymes (CAZymes) accordingly. Also, we identified a total of 793 SNPs arisen in probiotic administration in the indigenous microbiome. Over 90% of them derived from Bacteroides species, which involved genes encoding transposase, CAZymes, and membrane proteins. However, neither GOS supplementation here de-escalated the overall adaptive mutations within the indigenous microbes during probiotic intake. Collectively, our study demonstrated the beneficial effect of continuous prebiotic supplementation on the ecological and genetic stability of gut microbiomes.     

痛泻要方对醋酸-电刺激大鼠实验性肠易激综合征作用的研究

[目的]探讨痛泻要方对醋酸-电刺激大鼠实验性肠易激综合征（IBS）的作用及其机制。[方法]给予大鼠慢性反复直结肠灌注醋酸造成炎症刺激,炎症恢复后予小量电刺激诱发高敏感性的肠道发生应激反应,模拟人类IBS,观察痛泻要方对刺激期间大鼠排便量、粪便含水量、血浆P物质（SP）和血管活性肠肽（VIP）水平等各项指标的影响。[结果]模型组与正常组比较,大鼠排便量、粪便含水量增加（P〈0.01）,血浆SP和VIP减少（P〈0.05）;痛泻要方高剂量组与模型组比较,大鼠的排便量、粪便含水量减少（P〈0.05）,血浆SP和VIP增加（P〈0.05）。[结论]醋酸-电刺激大鼠模型可有效模拟人类IBS,痛泻要方能够改善该模型的排便加速、粪便含水量增加、血浆SP和VIP水平紊乱等症状。     

Lessons from mother: Long-term impact of antibodies in breast milk on the gut microbiota and intestinal immune system of breastfed offspring

From birth to adulthood, the gut microbiota matures from a simple community dominated by a few major bacterial groups into a highly diverse ecosystem that provides both benefits and challenges to the host. Currently there is great interest in identifying environmental and host factors that shape the development of our gut microbiota. Breast milk is a rich source of maternal antibodies, which provide the first source of adaptive immunity in the newborn''s intestinal tract. In this addendum, we summarize our recent data demonstrating that maternal antibodies in breast milk promote long-term intestinal homeostasis in suckling mice by regulating the gut microbiota and host gene expression. We also discuss important unanswered questions, future directions for research in this field, and implications for human health and disease.     

Lessons from mother: Long-term impact of antibodies in breast milk on the gut microbiota and intestinal immune system of breastfed offspring

From birth to adulthood, the gut microbiota matures from a simple community dominated by a few major bacterial groups into a highly diverse ecosystem that provides both benefits and challenges to the host. Currently there is great interest in identifying environmental and host factors that shape the development of our gut microbiota. Breast milk is a rich source of maternal antibodies, which provide the first source of adaptive immunity in the newborn's intestinal tract. In this addendum, we summarize our recent data demonstrating that maternal antibodies in breast milk promote long-term intestinal homeostasis in suckling mice by regulating the gut microbiota and host gene expression. We also discuss important unanswered questions, future directions for research in this field, and implications for human health and disease.     

Effects of fecal microbiota transplantation in subjects with irritable bowel syndrome are mirrored by changes in gut microbiome

ABSTRACT

Irritable bowel syndrome (IBS) is a common disorder of the lower gastrointestinal tract. The pathophysiology is far from settled, but a gut microbial dysbiosis is hypothesized to be a contributing factor. We earlier published a randomized double-blind placebo-controlled clinical trial on fecal microbiota transplantation (FMT) for IBS – the REFIT trial. The present data set describes the engraftment and includes participants from the study who received active FMT; 14 participants with effect of FMT (Effect) and 8 without (No effect). Samples were collected at baseline, after 6 and 12 months. Samples from the transplants (Donor) served as a comparator. In total 66 recipient samples and 17 donor samples were subjected to deep metagenomic sequencing, and taxonomic and functional analyses were performed. Alpha diversity measures showed a significantly increased diversity and evenness in the IBS groups compared to the donors. Taxonomic profiles showed higher relative abundance of phylum Firmicutes, and lower relative abundance of phylum Bacteroidetes, compared to donors at baseline. This profile was shifted toward the donor profile following FMT. Imputed growth rates showed that the resulting growth pattern was a conglomerate of donor and recipient activity. Thirty-four functional subclasses showed distinct differences between baseline samples and donors, most of which were shifted toward a donor-like profile after FMT. All of these changes were less pronounced in the No effect group. We conclude that FMT induces long-term changes in gut microbiota, and these changes mirror the clinical effect of the treatment. The study was registered in ClinicalTrials.gov (NCT02154867).