Sulfate-reducing bacteria colonize pouches formed for ulcerative colitis but not for familial adenomatous polyposis

The aetiology of pouchitis in patients with inflammatory bowel disease

Restorative proctocolectomy with ileal pouch-anal anastomosis is a treatment option for patients with refractory ulcerative colitis. Pouchitis is the most common complication, representing a spectrum of diseases ranging from acute antibiotic-responsive type to chronic antibiotic-refractory. Early accurate diagnosis using a combined assessment of symptoms, endoscopy and histology is important for both treatment and prognostication. Most patients respond well to antibiotic therapy; however, management of chronic antibiotic-refractory pouchitis remains a challenge, and treatment options are based on small studies. Pouchitis is thought to be driven by the interaction between genetics, the immune system and the environment but as yet a causal relationship has yet to be identified. Further longitudinal assessment of the pouch integrating new technologies may help us understand the factors driving pouchitis. This review outlines the currently understood risk factors and aetiology of pouchitis.

Ouch, my pouch! a clinician's guide to pouchitis

Pouchitis is defined as inflammation of the ileal pouch created during a restorative proctocolectomy with ileal pouch-anal anastomosis. Although the incidence of this inflammatory condition is high, the exact etiology often remains unclear and the management challenging. In this review, we summarize the clinical presentation, pathogenesis, diagnosis, and management of this common complication.

Cancer in the Anal Transition Zone and Ileoanal Pouch following Surgery for Ulcerative Colitis

Restorative proctocolectomy with ileal pouch-anal anastomosis remains the gold standard treatment for patients with ulcerative colitis who desire restoration of intestinal continuity. Despite a significant cancer risk reduction after surgical removal of the colon and rectum, dysplasia and cancers of the ileal pouch or anal transition zone still occur and are a risk even if an anal canal mucosectomy is performed. Surgical care and maintenance after ileoanal anastomosis must include consideration of malignant potential along with other commonly monitored variables such as bowel function and quality of life. Cancers and dysplasia of the ileal pouch are rare but sometimes difficult-to-manage sequelae of pouch surgery.

Altered gut microbiota community structure and correlated immune system changes in dibutyl phthalate exposed mice

Di-n-butyl phthalate (DBP) is a ubiquitous environmental contaminant linked with various adverse health effects, including immune system dysfunction. Gut microbial dysbiosis can contribute to a wide range of pathogenesis, particularly immune disease. Here, we investigated the impact of DBP on the gut microbiome and examined correlations with immune system changes after five weeks oral exposure (10 or 100 mg/kg/day) in adult male mice. The fecal microbiome composition was characterized using 16S rRNA sequencing. DBP-treated mice displayed a significantly distinct microbial community composition, indicated by Bray-Curtis distance. Numerous amplicon sequence variants (ASVs) at the genus level were altered. Compared to the vehicle control group, the 10 mg/kg/day DBP group had 63 more abundant and 65 less abundant ASVs, while 60 ASVs were increased and 76 ASVs were decreased in the 100 mg/kg/day DBP group. Both DBP treatment groups showed higher abundances of ASVs assigned to Desulfovibrio (Proteobacteria phylum) and Enterorhabdus genera, while ASVs belonging to Parabacteroides, Lachnospiraceae UCG-006 and Lachnoclostridium were less common compared to the control group. Interestingly, an ASV belonging to Rumniniclostridium 6, which was less abundant in DBP-treated mice, demonstrated a negative correlation with the increased number of non-classical monocytes observed in the blood of DBP-treated animals. In addition, an ASV from Lachnospiraceae UCG-001, which was more abundant in the DBP-treated animals, showed a positive correlation with the non-classical monocyte increase. This study shows that DBP exposure greatly modifies the gut bacterial microbiome and indicates a potential contribution of microbial dysbiosis to DBP-induced immune system impairment, illustrating the importance of investigating how interactions between exposome components can affect health.

Plasticity of the adult human small intestinal stoma microbiota

The human distal small intestine (ileum) has a distinct microbiota, but human studies investigating its composition and function have been limited by the inaccessibility of the ileum without purging and/or deep intubation. We investigated inherent instability, temporal dynamics, and the contribution of fed and fasted states using stoma samples from cured colorectal cancer patients as a non-invasive access route to the otherwise inaccessible small and large intestines. Sequential sampling of the ileum before and after stoma formation indicated that ileostoma microbiotas represented that of the intact small intestine. Ileal and colonic stoma microbiotas were confirmed as distinct, and two types of instability in ileal host-microbial relationships were observed: inter-digestive purging followed by the rapid postprandial blooming of bacterial biomass and sub-strain appearance and disappearance within individual taxa after feeding. In contrast to the relative stability of colonic microbiota, the human small intestinal microbiota biomass and its sub-strain composition can be highly dynamic.

Ileal Pouch-Anal Anastomosis and Pouchitis: The Role of the Microbiota in the Pathogenesis and Therapy

Inflammatory bowel diseases, Crohn's disease and ulcerative colitis, are life-long disorders characterized by the chronic relapsing inflammation of the gastrointestinal tract with the intermittent need for escalation treatment and, eventually, even surgery. The total proctocolectomy with ileal pouch-anal anastomosis (IPAA) is the surgical intervention of choice in subjects affected by ulcerative colitis (UC). Although IPAA provides satisfactory functional outcomes, it can be susceptible to some complications, including pouchitis as the most common. Furthermore, 10-20% of the pouchitis may develop into chronic pouchitis. The etiology of pouchitis is mostly unclear. However, the efficacy of antibiotics in pouchitis suggests that the dysbiosis of the IPAA microbiota plays an important role in its pathogenesis. We aimed to review the role of the microbiota in the pathogenesis and as a target therapy in subjects who develop pouchitis after undergoing the surgical intervention of total proctocolectomy with IPAA reconstruction.

Incidence and Risk Factors of Cancer in the Anal Transitional Zone and Ileal Pouch following Surgery for Ulcerative Colitis and Familial Adenomatous Polyposis

Proctocolectomy with ileal pouch-anal anastomosis is the intervention of choice for ulcerative colitis and familial adenomatous polyposis requiring surgery. One of the long-term complications is pouch cancer, having a poor prognosis. The risk of high-grade dysplasia and cancer in the anal transitional zone and ileal pouch after 20 years is estimated to be 2 to 4.5% and 3 to 10% in ulcerative colitis and familial polyposis, respectively. The risk factors for ulcerative colitis are the presence of pre-operative dysplasia or cancer, disease duration > 10 years and severe villous atrophy. For familial polyposis, the risk factors are the number of pre-operative polyps > 1000, surgery with stapled anastomosis and the duration of follow-up. In the case of ulcerative colitis, a pouchoscopy should be performed annually if one of the following is present: dysplasia and cancer at surgery, primary sclerosing cholangitis, villous atrophy and active pouchitis (every 5 years without any of these factors). In the case of familial polyposis, endoscopy is recommended every year including chromoendoscopy. Even if anal transitional zone and ileal pouch cancers seldom occur following proctectomy for ulcerative colitis and familial adenomatous polyposis, the high mortality rate associated with this complication warrants endoscopic monitoring.

Metabolic Influences of Gut Microbiota Dysbiosis on Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are chronic medical disorders characterized by recurrent gastrointestinal inflammation. While the etiology of IBD is still unknown, the pathogenesis of the disease results from perturbations in both gut microbiota and the host immune system. Gut microbiota dysbiosis in IBD is characterized by depleted diversity, reduced abundance of short chain fatty acids (SCFAs) producers and enriched proinflammatory microbes such as adherent/invasive E. coli and H₂S producers. This dysbiosis may contribute to the inflammation through affecting either the immune system or a metabolic pathway. The immune responses to gut microbiota in IBD are extensively discussed. In this review, we highlight the main metabolic pathways that regulate the host-microbiota interaction. We also discuss the reported findings indicating that the microbial dysbiosis during IBD has a potential metabolic impact on colonocytes and this may underlie the disease progression. Moreover, we present the host metabolic defectiveness that adds to the impact of symbiont dysbiosis on the disease progression. This will raise the possibility that gut microbiota dysbiosis associated with IBD results in functional perturbations of host-microbiota interactions, and consequently modulates the disease development. Finally, we shed light on the possible therapeutic approaches of IBD through targeting gut microbiome.

Desulfovibrio desulfuricans aggravates atherosclerosis by enhancing intestinal permeability and endothelial TLR4/NF-κB pathway in Apoe mice

It is increasingly aware that gut microbiota is closely associated with atherosclerosis. However, which and how specific gut bacteria regulate the progression of atherosclerosis is still poorly understood. In this study, modified linear discriminant analysis was performed in comparing the gut microbiota structures of atherosclerotic and non-atherosclerotic mice, and Desulfovibrio desulfuricans (D. desulfuricans) was found to be associated with atherosclerosis. D. desulfuricans-treated Apoe ^-/- mice showed significantly aggravated atherosclerosis. The proatherogenic effect of D. desulfuricans was attributed to its ability to increase intestinal permeability and subsequent raise in the transit of lipopolysaccharide (LPS) from the intestine to the bloodstream. Excessive LPS in the blood can elicit local and systemic inflammation and activate Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling of endothelial cells. TAK-242, a specific inhibitor of TLR4, can ameliorate the development of D. desulfuricans-induced atherosclerosis by blocking the LPS-induced activation of TLR4/NF-κB signaling.

Association Between Pouchitis and Ulcerative Colitis–Related Gastroduodenitis After Restorative Proctocolectomy

Background

Ulcerative colitis (UC)–related disorders, which include pouchitis and gastroduodenitis (GDUC), can develop even after restorative proctocolectomy (RPC). However, the etiology of and predictive factors for these disorders remain unclear.

Aim

We analyzed the incidence and associations between pouchitis and GDUC.

Methods

UC patients who underwent RPC at the Hyogo College of Medicine between 2009 and 2012 were included in this study. The postoperative results of examinations and the clinical courses were analyzed.

Results

A total of 122 patients examined by endoscopy after RPC out of 188 patients who underwent follow-up at the outpatient clinic were included. Pouchitis developed in 56 of 188 patients. The cumulative incidence of pouchitis was 32.1% at 5 years. GDUC was identified in 14 of 122 patients. In the Cox regression analyses, GDUC was selected as an independent predictive factor for pouchitis (hazard ratio, 2.32; P = 0.025).

Conclusion

An association between GDUC and pouchitis after RPC was found. However, this association should be evaluated in a further study because both complications might exist coincidentally as components of a systemic immune disorder, and the etiology of each complication should be determined.

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

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

Dietary Factors in Sulfur Metabolism and Pathogenesis of Ulcerative Colitis

The biogeography of inflammation in ulcerative colitis (UC) suggests a proximal to distal concentration gradient of a toxin. Hydrogen sulfide (H₂S) has long been considered one such toxin candidate, and dietary sulfur along with the abundance of sulfate reducing bacteria (SRB) were considered the primary determinants of H₂S production and clinical course of UC. The metabolic milieu in the lumen of the colon, however, is the result of a multitude of factors beyond dietary sulfur intake and SRB abundance. Here we present an updated formulation of the H₂S toxin hypothesis for UC pathogenesis, which strives to incorporate the interdependency of diet composition and the metabolic activity of the entire colon microbial community. Specifically, we suggest that the increasing severity of inflammation along the proximal-to-distal axis in UC is due to the dilution of beneficial factors, concentration of toxic factors, and changing detoxification capacity of the host, all of which are intimately linked to the nutrient flow from the diet.

Removal of sulfate and heavy metals by sulfate-reducing bacteria in an expanded granular sludge bed reactor

The objective of this study is to utilize an expanded granular sludge bed reactor for removing heavy metals and sulfate from synthetic acid-mine drainage (AMD) using sewage sludge fermentation centrate as the substrate. The reactor was bioaugmented with an enriched consortium of sulfate-reducing bacteria (SRB). The bioreactor performance was studied with different chemical oxygen demand [Formula: see text] ratios, liquid upflow velocity (V_up), hydraulic retention time (HRT) and influent pH. The highest COD, sulfate and heavy metal removal efficiencies were achieved at a [Formula: see text] ratio of 1.5, V_up of 4.0 m/h, HRT of 15 h and influent pH of 6.0 (68.2%, 92.1% and 100%, respectively). The activity of SRB greatly increases the effluent pH. Even at an influent pH of 3.0, 60.8% of sulfate, 41.3% of COD and 91.2% of heavy metals could be removed, and the effluent quality can meet the national discharge standard of China. The activity tests demonstrate that the sludge fermentation centrate is an excellent carbon source for SRB. This study shows the potential of synchronous treatment of residual sewage sludge and treatment of AMD.

Impact of Qi-invigorating traditional Chinese medicines on intestinal flora: A basis for rational choice of prebiotics

According to the theory of traditional Chinese medicine (TCM), Qi (vital energy) is regarded as a driving force of biological activities in human body, including both nutrient substances and organ functions. Qi-invigorating TCMs are widely used to treat various symptoms and disorders, such as fatigue, obesity, immunosuppression, intestinal flora imbalance, and gastrointestinal diseases, in which Qi is considered to be reduced or depleted. Interestingly, abundant clinical evidences suggest that these disorders are associated with the alternation of intestinal flora, which directly affects disease status. Herein we review the interaction between gut microbiota and Qi-invigorating TCMs under healthy and disease conditions and discuss the mechanisms of action and applications of Qi-invigorating TCMs in enhancing health status through microbial alternation. A better understanding of the role of Qi-invigorating TCMs in modulating microbial composition and the association between intestinal microbiota and diseases would help reveal the clinical consequences of microbiota alteration and explore opportunities to harness this symbiotic relationship to improve public health.

Festschrift for Ronan O'Connell: pouchitis, ulcerative colitis and the microbiome

The hypothesis of altered bacterial communities contributing to the development of pouchitis began a scientific quest to link host mucosal factors, microbial metabolism and spatial structure of the colonic microbiome in ulcerative colitis, reaching its apotheosis with the integration of advanced spatial sampling with laser capture microdissection, mucin array profiling, molecular microbiology and next-generation sequencing technologies. This article, part of a festschrift, summarises the contributions of the O'Connell lab to the field of host-microbial interactions in inflammatory bowel disease.

Systematic review: ileoanal pouch microbiota in health and disease

BACKGROUND

The resident gut microbiota is essential for physiological processes; the disturbance of its balance is linked to intestinal inflammation. The ileoanal pouch is a model for the study of intestinal inflammation, as inflammation of the pouch is common and mostly develops within 12 months following ileostomy closure. This allows the longitudinal study of the microbiota, giving insight into the microbiota changes during transition from a normal to an inflamed pouch.

AIM

To explore the literature on the microbiota of the ileoanal pouch in health and disease.

METHODS

A systematic computer search of the on-line bibliographic databases MEDLINE and EMBASE was performed between 1966 and February 2017. Randomised controlled trials, cohort studies and observational studies were included. Studies were included if they reported microbiota analysis on faecal samples or tissue from the ileoanal pouch.

RESULTS

Twenty-six papers were eligible. Following ileostomy closure, anaerobic bacteria are the abundant species in the ileoanal pouch with presence of a diverse microbiota key to maintaining a healthy ileoanal pouch. Acute pouchitis is associated with an increase in Clostridia species, while chronic pouchitis is associated with an increase in Staphylococcus aureus. In the treatment of pouchitis, a decrease in Clostridia species appears to be associated with treatment response.

CONCLUSION

The microbiota plays an important role in both the inflamed and the healthy ileoanal pouch. A direct causal relationship between individual microbiota changes and inflammation has not yet been established, but manipulation of the ileoanal pouch microbiota may be a novel therapeutic avenue to explore.

Pouch-Related Symptoms and Quality of Life in Patients with Ileal Pouch-Anal Anastomosis

BACKGROUND

Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) has become the standard surgical treatment for the majority of patients with inflammatory bowel disease (IBD) who require colectomy. We evaluated the prevalence of pouch-related symptoms among the Crohn's and Colitis Foundation of America Partners cohort and the effect of pouch-related symptoms on Patient-Reported Outcome Measurement Information System measures.

METHODS

We performed analyses nested in the Crohn's and Colitis Foundation of America Partners cohort. We used bivariate analyses to compare demographics and medication use among patients with ulcerative colitis or indeterminate colitis and pouch-related symptoms and those with IPAA without symptoms. We also compared Patient-Reported Outcome Measurement Information System domains (measured in T-scores) and short IBD questionnaire quality of life scales between symptomatic pouch patients (over the past 6 mo) and those without symptoms.

RESULTS

Among 243 patients reporting a history of IPAA, 199 (82%) reported a history of pouch symptoms. Patients with recent pouch symptoms demonstrated higher mean T-scores in pain interference (53.0 versus 45.3; P < 0.001), depression (51.0 versus 46.4; P = 0.002), and fatigue (56.3 versus 47.0; P < 0.001). Symptomatic pouch patients reported lower mean scores in social role satisfaction (47.4 versus 54.6) and short IBD questionnaire (4.8 versus 5.8) (both P < 0.001). These differences were all clinically meaningful.

CONCLUSIONS

In a large sample of patients with IBD, nearly all patients with IPAA reported a history of pouch symptoms. Patients experiencing symptoms within the 6 months before the survey assessment demonstrated clinically meaningful decrements in patient-reported outcomes in multiple domains of physical and psychosocial functioning.

Sulfasalazine in Prevention of Pouchitis After Proctocolectomy with Ileal Pouch-Anal Anastomosis for Ulcerative Colitis

BACKGROUND

Pouchitis is the most frequent complication after ileal pouch-anal anastomosis for refractory ulcerative colitis. A non-standardized preventative treatment exists. Sulfasalazine has proved effective in acute pouchitis therapy.

AIMS

The aim of this study was to retrospectively evaluate the effect of sulfasalazine in primary prophylaxis of pouchitis after proctocolectomy with ileal pouch-anal anastomosis.

METHODS

Data files of patients who underwent total proctocolectomy with ileal pouch-anal anastomosis for refractory ulcerative colitis and/or dysplasia from January 2007 to December 2014, with a follow-up until August 2015, were analyzed. After closure of loop ileostomy, on a voluntary basis, patients received a primary prophylaxis of pouchitis with sulfasalazine (2000 mg per day) continually until acute pouchitis flare and/or drop out due to side effects.

RESULTS

Follow-up data were available for 51 of the 55 surgical patients. Median follow-up time was 68 months (range 10-104). Thirty postoperative complications occurred in 25 patients. 45% of patients developed pouchitis. Sulfasalazine prophylaxis was administered in 39.2% of patients; 15% of the these developed pouchitis versus 64.5% (20/31) of the non-sulfasalazine patients (p < 0.001). Pouchitis-free survival curves were 90.55 months in sulfasalazine patients and 44.46 in non-sulfasalazine patients (log-rank test p = 0.001, Breslow p = 0.001).

CONCLUSION

Sulfasalazine may be potentially administered in pouchitis prophylaxis after proctocolectomy with ileal pouch-anal anastomosis, but large prospectively controlled trials are needed.

Host-microbial Cross-talk in Inflammatory Bowel Disease

A vast community of commensal microorganisms, commonly referred to as the gut microbiota, colonizes the gastrointestinal tract (GI). The involvement of the gut microbiota in the maintenance of the gut ecosystem is two-fold: it educates host immune cells and protects the host from pathogens. However, when healthy microbial composition and function are disrupted (dysbiosis), the dysbiotic gut microbiota can trigger the initiation and development of various GI diseases, including inflammatory bowel disease (IBD). IBD, primarily includes ulcerative colitis (UC) and Crohn's disease (CD), is a major global public health problem affecting over 1 million patients in the United States alone. Accumulating evidence suggests that various environmental and genetic factors contribute to the pathogenesis of IBD. In particular, the gut microbiota is a key factor associated with the triggering and presentation of disease. Gut dysbiosis in patients with IBD is defined as a reduction of beneficial commensal bacteria and an enrichment of potentially harmful commensal bacteria (pathobionts). However, as of now it is largely unknown whether gut dysbiosis is a cause or a consequence of IBD. Recent technological advances have made it possible to address this question and investigate the functional impact of dysbiotic microbiota on IBD. In this review, we will discuss the recent advances in the field, focusing on host-microbial cross-talk in IBD.

Pouchitis after ileal pouch-anal anastomosis in ulcerative colitis: Diagnosis, management, risk factors, and incidence

Restorative proctocolectomy with ileal pouch-anal anastomosis has been the surgical treatment of choice for patients with ulcerative colitis who require surgery. Quality of life after this procedure is satisfactory in most cases; however, pouchitis is a troublesome condition involving inflammation of the ileal pouch. When a patient presents with symptoms of pouchitis, such as increased bowel movements, mucous and/or bloody exudates, abdominal cramps, and fever, endoscopy is essential for a precise diagnosis. The proximal ileum and rectal cuff, as well as the ileal pouch, should be endoscopically observed. The reported incidence of pouchitis ranges from 14% to 59%, and antibiotic therapy is the primary treatment for acute pouchitis. Chronic pouchitis includes antibiotic-dependent and refractory pouchitis. Intensive therapy including antitumor necrosis factor antibodies and steroids may be necessary for antibiotic-refractory pouchitis, and pouch failure may occur despite such intensive treatment. Reported risk factors for the development of pouchitis include presence of extraintestinal manifestations, primary sclerosing cholangitis, non-smoking, and postoperative non-steroidal anti-inflammatory drug usage. In the present review, we focus on the diagnosis, endoscopic features, management, incidence, and risk factors of pouchitis in patients with ulcerative colitis who underwent ileal pouch-anal anastomosis.

Review article: the pathogenesis of pouchitis

BACKGROUND

A total proctocolectomy followed by ileal pouch-anal anastomosis is a potentially curative surgery for ulcerative colitis or familial adenomatous polyposis. About 5-35% of patients with ulcerative colitis and 0-11% of patients with familial adenomatous polyposis develop subsequent inflammation of the ileal pouch termed pouchitis.

AIM

To provide a comprehensive analysis of the research studying the possible pathogenesis of pouchitis. The goals were to identify promising areas of investigation, to help focus clinicians, researchers and patients on how to better understand and then potentially manage ileal pouchitis, and to provide avenues for future research investigations.

METHODS

This review examined manuscripts from 1981 to 2015 that discussed and/or proposed hypotheses with supportive evidence for the potential underlying pathogenic mechanism for pouchitis.

RESULTS

The pathogenesis of pouchitis is not definitively understood, but various hypotheses have been proposed, including (i) recurrence of ulcerative colitis, (ii) dysbiosis of the ileal pouch microbiota, (iii) deprivation of nutritional short-chain fatty acids, (iv) mucosal ischaemia and oxygen-free radical injury, (v) host genetic susceptibility and (vi) immune dysregulation. However, none of these alone are able to fully explain pouchitis pathogenesis.

CONCLUSIONS

Pouchitis, similar to inflammatory bowel disease, is a complex disorder that is not caused by any one single factor. More likely, pouchitis occurs through a combination of both dysregulated host inflammatory mechanisms and interaction with luminal microbiota.

Intestinal barrier dysfunction: implications for chronic inflammatory conditions of the bowel

The intestinal epithelium of adult humans acts as a differentially permeable barrier that separates the potentially harmful contents of the lumen from the underlying tissues. Any dysfunction of this boundary layer that disturbs the homeostatic equilibrium between the internal and external environments may initiate and sustain a biochemical cascade that results in inflammation of the intestine. Key to such dysfunction are genetic, microbial and other environmental factors that, singularly or in combination, result in chronic inflammation that is symptomatic of inflammatory bowel disease (IBD). The aim of the present review is to assess the scientific evidence to support the hypothesis that defective transepithelial transport mechanisms and the heightened absorption of intact antigenic proinflammatory oligopeptides are important contributing factors in the pathogenesis of IBD.

Problems after restorative proctocolectomy: assessment and therapy

PURPOSE OF REVIEW

Restorative proctocolectomy with ileal pouch-anal anastomosis is the surgical treatment of choice for patients with ulcerative colitis or familial adenomatous polyposis who require colectomy. Although the surgical procedure significantly improves the patients' quality of life, complications are common. Mechanical or structural complications related to surgical techniques as well as chronic pouchitis are common after the procedure.

RECENT FINDINGS

Recent literature has suggested some of those mechanical complications, along with chronic pouchitis, may share similar risk factors, particularly between anastomotic leak or sinus and chronic pouchitis. Those factors include male gender, obesity, weight gain, and Clostridium difficile infection.

SUMMARY

Mounting clinical evidence suggests that ischemia or excessive fat deposition plays an important role in the development of the surgical procedure-associated mechanical complication as well as chronic antibiotic-refractory pouchitis. Those findings along with the theory of ischemia/fat deposition will shed some light on the pathogenesis of the complex pouch disorders, providing the guidance for the risk stratification, prevention, diagnosis, and management.

Use of Biologics in Pouchitis: A Systematic Review

Data about the effectiveness of biologics, including anti-tumor necrosis factor (TNF) therapy and anti-integrin strategies, in antibiotic refractory pouchitis or Crohn's disease-associated pouch complications are sparse. We performed a systematic review of the literature in Medline and Web of Science. All English language publications and meeting abstracts describing patients with pouchitis treated with anti-TNF or anti-integrin therapies were included. We identified a total of 17 papers and 2 abstracts, most of these retrospective case series, including a total of 192 patients treated either with infliximab (n=140) or adalimumab (n=52). No reports were found for anti-integrin therapies or other anti-TNF agents such as certolizumab pegol or golimumab. Because of the heterogeneity of the studies, small numbers of patients, differing cotreatments, and subjective outcome definitions, the exact efficacy of these biological therapies cannot be assessed in a combined fashion. Overall infliximab appears to have good clinical effectiveness in selected patients achieving up to 80% short-term and around 50% long-term response, whereas the few data available for adalimumab are not sufficient to draw valid conclusions. Larger prospectively collected multicenter data with clearly defined inclusion criteria and outcomes are necessary to better define the clinical value of anti-TNF therapy in patients with antibiotic refractory pouchitis or Crohn's-like complications of the pouch.

Frequency and risk factors of low immunoglobulin levels in patients with inflammatory bowel disease

Background and aims: Inflammatory bowel diseases (IBD) are considered to be dysregulated, immune-mediated disorders; and immunosuppressive medications are the mainstay of their treatment. Clinically, we have often observed low serum immunoglobulin (Ig) levels in these patients. The aim of this study was to assess the frequency and risk factors of secondary humoral immunodeficiency in IBD patients.

Methods: We conducted a cross-sectional study of eligible IBD patients with Crohn’s disease (CD), ulcerative colitis (UC), indeterminate colitis (IC) or restorative proctocolectomy with ileal pouch, who having serum Ig measured. Demographic and clinical variables were measured. Univariate and multivariate analyses were performed.

Results: A total of 324 patients was included, with a mean age of 38.8 years and 158 (48.8%) being male. Low IgG, IgG1, IgA, and IgM were found in 22.7%, 23.4%, 7.9%, and 10.9% of patients, respectively. The shared risk factors for a low IgG or IgM level were increasing age [odds ratio (OR) = 1.13; 95% confidence interval (CI) 1.03–1.23 for low IgG level and OR = 1.33; 95% CI 1.15–1.56 for low IgM level] and hypoalbuminemia (OR = 1.83; 95% CI 1.01–3.33 for low IgG level and OR = 3.17; 95% CI 1.23–8.15 for low IgM level). In addition, thioprine use was associated with low IgA level (OR = 2.76; 95% CI 1.03–7.39). IBD disease duration was a risk factor for low IgG1 level (OR = 1.40; 95% CI 1.12–1.76). The presence of concurrent primary sclerosing cholangitis (OR = 0.064; 95% CI 0.007–0.60) and the use of biologics (OR = 0.16; 95% CI 0.033–0.79) were associated with normal IgG1 level. IgG level was lower in CD patients than that in UC/IC and ileal pouch patients (P = 0.042). IgG and IgA levels were elevated in patients with inflammatory conditions of the pouch (P = 0.01; P = 0.003, respectively).

Conclusions: Low Ig level appears to be common in IBD patients. Increasing age, disease duration and hypoalbuminemia appeared to be risk factors. The findings may provide rationale for targeted therapy to boost humoral immunity in selected patients with IBD.

Update on the pathogenesis and management of pouchitis

Pouchitis is an inflammatory complication after restorative proctocolectomy and ileal pouch-anal anastomosis (IPAA). IPAA is the surgical treatment of choice in patients with ulcerative colitis (UC) who require colectomy. Initial episodes of acute pouchitis generally respond to antibiotics but significant numbers of cases eventually become dependent on or refractory to antibiotics. Management of chronic antibiotic refractory pouchitis is challenging and can ultimately lead to pouch failure. The etiopathogenesis is unknown though recent studies have implicated bacterial dysbiosis of the pouch microbiota, NOD2 polymorphism, and Clostridium difficile infection in the development of severe pouchitis. Early identification of risk factors can help in tailoring therapy and reducing cases of chronic pouchitis.

Relationship between pouch microbiota and pouchitis following restorative proctocolectomy for ulcerative colitis

Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) has become the surgical treatment of choice for many patients with medically refractory ulcerative colitis (UC) and familial adenomatous polyposis (FAP). UC patients with IPAA (UC-IPAA) are, nevertheless, susceptible to inflammatory and noninflammatory sequelae such as pouchitis, which is only rarely noted in FAP patients with IPAA. Pouchitis is the most frequent long-term complication of UC-IPAA patients, with a cumulative prevalence of up to 50%. Although the aetiology of pouchitis remains unclear, accumulating evidence suggests that a dysbiosis of the pouch microbiota and an abnormal mucosal immune response are implicated in its pathogenesis. Studies using culture and molecular techniques have detected a dysbiosis of the pouch microbiota in patients with pouchitis. Risk factors, genetic associations, and serological markers suggest that interactions between the host immune response and the pouch microbiota underlie the aetiology of this idiopathic inflammatory condition. This systematic review focuses on the dysbiosis of the microbiota that inhabit the pouch in UC and FAP patients and its interaction with the mucosal immune system. A meta-analysis was not attempted due to the highly heterogeneous microbiota composition and the different detection methods used by the various studies. Although no specific bacterial species, genus, or family has as yet been identified as pathogenic, there is evidence that a dysbiosis characterized by decreased gut microbiota diversity in UC-IPAA patients may, in genetically predisposed subjects, lead to aberrant mucosal immune regulation triggering an inflammatory process.

Role of intestinal bacteria in the pathogenesis of pouchitis

Pouchitis is a common complication seen in patients with ulcerative colitis who undergo total proctocolectomy with ileal pouch anal anastomosis. Bacteria seem to play an important role in the development of pouchitis, although this role is not well defined. Because technology has advanced, we are able to apply molecular techniques to describe the structure and function of the pouch microbial community. In recent years, several studies have been performed comparing the pouch microbiota in patients with ulcerative colitis with healthy pouches and pouchitis. Many of these studies have suggested that pouchitis is characterized by dysbiosis and/or decreased microbial diversity. There has not been a clear pattern identifying a pathogenic organism or a group of organisms responsible for pouchitis. This review summarizes recent studies exploring the pouch microbiota in health and disease, the relationship of bacterial metabolites and pouchitis, and the role of antibiotics and probiotics for the treatment and prevention of pouchitis.

Influences of the colonic microbiome on the mucous gel layer in ulcerative colitis

The colonic mucus gel layer (MGL) is a critical component of the innate immune system acting as a physical barrier to microbes, luminal insults, and toxins. Mucins are the major component of the MGL. Selected microbes have the potential to interact with, bind to, and metabolize mucins. The tolerance of the host to the presence of these microbes is critical to maintaining MGL homeostasis. In disease states such as ulcerative colitis (UC), both the mucosa associated microbes and the constituent MGL mucins have been shown to be altered. Evidence is accumulating that implicates the potential for mucin degrading bacteria to negatively impact the MGL and its stasis. These effects appear more pronounced in UC.   This review is focused on the host-microbiome interactions within the setting of the MGL. Special focus is given to the mucolytic potential of microbes and their interactions in the setting of the colitic colon.

Hydrogen sulfide signaling in the gastrointestinal tract

SIGNIFICANCE

The current literature regarding the effects of the gaseous signal molecule hydrogen sulfide (H2S) in the gastrointestinal system is reviewed. Bacterial, host and pharmaceutical-derived H2S are all considered and presented according to the physiological or pathophysiological effects of the gaseous signal molecule. These subjects include the toxicology of intestinal H2S with emphasis on bacterial-derived H2S, especially from sulfate-reducing bacteria, the role of endogenous and exogenous H2S in intestinal inflammation, and the roles of H2S in gastrointestinal motility, secretion and nociception.

RECENT ADVANCES

While its pro- and anti-inflammatory, smooth muscle relaxant, prosecretory, and pro- and antinociceptive actions continue to remain the major effects of H2S in this system; recent findings have expanded the potential molecular targets for H2S in the gastrointestinal tract.

CRITICAL ISSUES

Numerous discrepancies remain in the literature, and definitive molecular targets in this system have not been supported by the use of competitive antagonism.

FUTURE DIRECTIONS

Future work will hopefully resolve discrepancies in the literature and identify molecular targets and mechanisms of action for H2S. It is clear from the current literature that the long-appreciated relationship between H2S and the gastrointestinal tract continues to be strong as we endeavor to unravel its mysteries.

Pouchitis: what every gastroenterologist needs to know

Pouchitis is the most common complication among patients with ulcerative colitis who have undergone restorative proctocolectomy with ileal pouch-anal anastomosis. Pouchitis is actually a spectrum of diseases that vary in etiology, pathogenesis, phenotype, and clinical course. Although initial acute episodes typically respond to antibiotic therapy, patients can become dependent on antibiotics or develop refractory disease. Many factors contribute to the course of refractory pouchitis, such as the use of nonsteroidal anti-inflammatory drugs, infection with Clostridium difficile, pouch ischemia, or concurrent immune-mediated disorders. Identification of these secondary factors can help direct therapy.

The effects of probiotics on barrier function and mucosal pouch microbiota during maintenance treatment for severe pouchitis in patients with ulcerative colitis

BACKGROUND

A total of 10-15% of patients with an ileoanal pouch develop severe pouchitis necessitating long-term use of antibiotics or pouch excision. Probiotics reduce the risk of recurrence of pouchitis, but mechanisms behind these effects are not fully understood.

AIM

To examine mucosal barrier function in pouchitis, before and after probiotic supplementation and to assess composition of mucosal pouch microbiota.

METHODS

Sixteen patients with severe pouchitis underwent endoscopy with biopsies of the pouch on three occasions: during active pouchitis; clinical remission by 4 weeks of antibiotics; after 8 weeks of subsequent probiotic supplementation (Ecologic 825, Winclove, Amsterdam, the Netherlands). Thirteen individuals with a healthy ileoanal pouch were sampled once as controls. Ussing chambers were used to assess transmucosal passage of Escherichia coli K12, permeability to horseradish peroxidase (HRP) and ⁵¹Cr-EDTA. Composition and diversity of the microbiota was analysed using Human Intestinal Tract Chip.

RESULTS

Pouchitis Disease Activity Index (PDAI) was significantly improved after antibiotic and probiotic supplementation. Escherichia coli K12 passage during active pouchitis [3.7 (3.4-8.5); median (IQR)] was significantly higher than in controls [1.7 (1.0-2.4); P < 0.01], did not change after antibiotic treatment [5.0 (3.3-7.1); P = ns], but was significantly reduced after subsequent probiotic supplementation [2.2 (1.7-3.3); P < 0.05]. No significant effects of antibiotics or probiotics were observed on composition of mucosal pouch microbiota; however, E. coli passage correlated with bacterial diversity (r = -0.40; P = 0.018). Microbial groups belonging to Bacteroidetes and Clostridium clusters IX, XI and XIVa were associated with healthy pouches.

CONCLUSIONS

Probiotics restored the mucosal barrier to E. coli and HRP in patients with pouchitis, a feasible factor in prevention of recurrence during maintenance treatment. Restored barrier function did not translate into significant changes in mucosal microbiota composition, but bacterial diversity correlated with barrier function.

From biocontrol to cancer, probiotics and beyond

This invited commentary covers the period 1997-2012 and has seen changes in terminology that progressed from "basic" and "applied" to "translational" research. In the context of Bioengineered, these changes map readily onto the processes of identifying microbial characteristics appropriate for specific applications, isolation of suitable cultures, strain or genome manipulation and exploitation of these or their metabolomes across a range of settings.   To a great degree, this commentary and my career reflect an engagement with molecular microbiology and the trialling of bacteria and derived constructs in applications ranging from intensive-scale crop protection to amelioration of gastrointestinal disease. This engagement began with laboratory and field evaluations of biocontrol, specifically use of pseudomonads effective against nematode and fungal plant pathogens, characterization of mechanisms mediating beneficial effects of probiotic lactobacilli and bifidobacteria and assessment of functional foods in multinational clinical trials relating to inflammatory bowel disease. Subsequent work focused on (1) intellectual property (IP)-based medical devices for localized delivery of systemically toxic and gene cancer therapies; (2) growth of the science base supporting expansion of a multinational business including company acquisitions; (3) complementing existing inter-institutional research capabilities through development of a national industry-led collaboration; and, most recently, (4) strategic research programs at Ireland's newest medical school. My activities as outlined above parallel two distinct aspects of translational research: (1) involvement in knowledge-driven (commercial and research) organizations that brought together necessary resources and infrastructure and (2) availability of scale research funding from European Framework and Irish national programs.

Chronic use of PPI and H2 antagonists decreases the risk of pouchitis after IPAA for ulcerative colitis

INTRODUCTION

Bacteria have been implicated in the development of pouchitis after ileal pouch anal anastomosis. The change in gastric pH with the use of proton pump inhibitors and H(2) antagonists may lead to alteration of enteric bacteria. We hypothesized that chronic use of these medications would decrease the incidence of pouchitis.

METHODS

Patients who had undergone ileal pouch anal anastomosis for ulcerative colitis were classified by history of pouchitis. Patients were further classified by their use of proton pump inhibitors, H(2) blockers, antacids, and other known risk factors for pouchitis.

RESULTS

Eighty-five patients were identified. There was a statistically significant increase in the use of daily acid suppression in patients without pouchitis. There was also a statistically significant increase in the use of antacids in patients without pouchitis. Occasional use of acid suppression did not alter the rate of pouchitis.

CONCLUSIONS

Our data suggest that the daily use of proton pump inhibitors, H(2) antagonists, or antacids is associated with a decreased risk of pouchitis in ulcerative colitis. Occasional use of these agents did not seem to afford the same protection. These data suggest that altering the pH of the gastrointestinal tract may influence the development of pouchitis.

Considerations and complications in patients undergoing ileal pouch anal anastomosis

Total proctocolectomy with ileal pouch anal anastomosis (IPAA) preserves fecal continence as an alternative to permanent end ileostomy in select patients with ulcerative colitis and familial adenomatous polyposis. The procedure is technically demanding, and surgical complications may arise. This article outlines both the early and late complications that can occur after IPAA, as well as the workup and management of these potentially morbid conditions.

Microbial pathways in colonic sulfur metabolism and links with health and disease

Sulfur is both crucial to life and a potential threat to health. While colonic sulfur metabolism mediated by eukaryotic cells is relatively well studied, much less is known about sulfur metabolism within gastrointestinal microbes. Sulfated compounds in the colon are either of inorganic (e.g., sulfates, sulfites) or organic (e.g., dietary amino acids and host mucins) origin. The most extensively studied of the microbes involved in colonic sulfur metabolism are the sulfate-reducing bacteria (SRB), which are common colonic inhabitants. Many other microbial pathways are likely to shape colonic sulfur metabolism as well as the composition and availability of sulfated compounds, and these interactions need to be examined in more detail. Hydrogen sulfide is the sulfur derivative that has attracted the most attention in the context of colonic health, and the extent to which it is detrimental or beneficial remains in debate. Several lines of evidence point to SRB or exogenous hydrogen sulfide as potential players in the etiology of intestinal disorders, inflammatory bowel diseases (IBDs) and colorectal cancer in particular. Generation of hydrogen sulfide via pathways other than dissimilatory sulfate reduction may be as, or more, important than those involving the SRB. We suggest here that a novel axis of research is to assess the effects of hydrogen sulfide in shaping colonic microbiome structure. Clearly, in-depth characterization of the microbial pathways involved in colonic sulfur metabolism is necessary for a better understanding of its contribution to colonic disorders and development of therapeutic strategies.

A shift from colon- to ileum-predominant bacteria in ileal-pouch feces following total proctocolectomy

BACKGROUND

We previously investigated fecal flora of the pouch after total proctocolectomy using terminal restriction fragment polymorphism analysis. Although the results of the cluster analysis demonstrated clearly that bacterial populations, including an unidentified bacteria generating a 213-bp PCR fragment, moved toward a colon-like community in the pouch, it did not track changes in the individual species of fecal bacteria.

AIMS

The aim of the present study was to estimate genome copy number of ten bacterial species, clusters, groups, or subgroups (including the bacteria generating 213-bp fragment in the previous study) in feces samples from pouches at various times following ileostomy closure.

METHODS

A total of 117 stool samples were collected from patients with ulcerative colitis after surgery as well as healthy volunteers. We used real-time polymerase chain reaction of the 16S rRNA gene to estimate genome copy numbers for the nine bacterial populations and the bacteria generating 213-bp fragment after identification by DNA sequencing.

RESULTS

We demonstrated a time-dependent increase in the number of anaerobic and colon-predominant bacteria (such as Clostridium coccoides, C. leptum, Bacteroides fragilis and Atopobium) present in proctocolectomy patients after stoma closure. In contrast, numbers of ileum-predominant bacterial species (such as Lactobacillus and Enterococcus faecalis) declined.

CONCLUSIONS

Our data confirm previous findings that fecal flora in the pouch after total proctocolectomy changes significantly, and further demonstrate that the number and diversity of ileal bacteria decreases while a more colon-like community develops. The present data are essential for the future analysis of pathological conditions in the ileal pouch.

Contributions of the microbial hydrogen economy to colonic homeostasis

Colonic gases are among the most tangible features of digestion, yet physicians are typically unable to offer long-term relief from clinical complaints of excessive gas. Studies characterizing colonic gases have linked changes in volume or composition with bowel disorders and shown hydrogen gas (H(2)), methane, hydrogen sulphide, and carbon dioxide to be by-products of the interplay between H(2)-producing fermentative bacteria and H(2) consumers (reductive acetogens, methanogenic archaea and sulphate-reducing bacteria [SRB]). Clinically, H(2) and methane measured in breath can indicate lactose and glucose intolerance, small intestinal bacterial overgrowth and IBS. Methane levels are increased in patients with constipation or IBS. Hydrogen sulphide is a by-product of H(2) metabolism by SRB, which are ubiquitous in the colonic mucosa. Although higher hydrogen sulphide and SRB levels have been detected in patients with IBD, and to a lesser extent in colorectal cancer, this colonic gas might have beneficial effects. Moreover, H(2) has been shown to have antioxidant properties and, in the healthy colon, physiological H(2) concentrations might protect the mucosa from oxidative insults, whereas an impaired H(2) economy might facilitate inflammation or carcinogenesis. Therefore, standardized breath gas measurements combined with ever-improving molecular methodologies could provide novel strategies to prevent, diagnose or manage numerous colonic disorders.

Bacteriology in the etiopathogenesis of pouchitis

BACKGROUND

Pouchitis is the most common long-term complication in ulcerative colitis that follows restorative proctocolectomy. Clinical evidence suggests that dysbiosis plays a key role in its pathogenesis.

METHODS

Current literature on the topic was reviewed. A therapeutic approach was proposed based on the literature along with personal experience from the subspecialty Pouchitis Clinic.

RESULTS

Pouchitis represents a disease spectrum in the reservoir, with ranging etiopathogenesis, clinical phenotypes, disease courses and prognoses. Dysbiosis plays a critical role in disease initiation and progress, with antibiotic therapy as the mainstay for treatment. On the other hand, superimposed infection from pathogens contributes to flare-up of the disease. Pouchitis can progress into an 'IBD-like' condition, requiring anti-inflammatory, immunomodulator or even biological therapy.

CONCLUSION

Pouchitis represents a unique form of IBD. Investigation on the evolution from an antibiotic-responsive phenotype to chronic antibiotic-refractory pouchitis may shed some light on the pathogenesis and therapeutic targets of IBD.

Etiology of pouchitis

Restorative proctocolectomy with ileal-pouch anal anastomosis (RPC) is the operation of choice for ulcerative colitis (UC) patients requiring surgery. It is also used for patients with familial adenomatous polyposis (FAP). Pouchitis accounts for 10% of pouch failures. It is an idiopathic inflammatory condition that may occur in up to 50% of patients after RPC for UC. It is rarely seen in FAP patients after RPC. The etiology of pouchitis remains unclear. An overlap with UC is suggested by the frequency with which pouchitis affects patients with UC compared with FAP patients. There is significant clinical evidence implicating bacteria in the pathogenesis of pouchitis. Studies using culture and molecular methods demonstrate a dysbiosis of the pouch microbiota in pouchitis. Risk factors, genetic associations, and serological markers of pouchitis suggest that the interactions between the host immune responses and the pouch microbiota underlie the etiology of this idiopathic inflammatory condition. Here we present a detailed review of the data focusing on the pouch microbiota and the immune responses that support this hypothesis. We also discuss the contribution of luminal metabolic factors and the epithelial membrane in the etiology of this inflammatory process. The ileoanal pouch offers a unique opportunity to study the inter-relationships between the gut microbiota and host immune responses from before the onset of disease. For this reason the study of pouchitis could serve as a human model that significantly enhances our understanding of inflammatory bowel diseases in general.

Comprehensive analysis of the bacterial content of stool from patients with chronic pouchitis, normal pouches, or familial adenomatous polyposis pouches

BACKGROUND

Chronic pouchitis is an important long-term complication following ileal pouch-anal anastomosis for ulcerative colitis. Antibiotic administration reduces symptoms of pouchitis, indicating that bacteria have a role in pathogenesis. The aim of the research was to investigate the bacterial content of pouches using nucleic acid-based methods.

METHODS

Stool microbiota of 17 patients with normal pouches (NP), 17 patients with pouchitis (CP) utilizing samples collected from each patient when antibiotic-treated (CP-on, asymptomatic) and when untreated (CP-off, symptomatic), and 14 familial adenomatous polyposis (FAP) patients were analyzed by high-throughput sequencing, fluorescence in situ hybridization technologies, and quantitative polymerase chain reaction (qPCR).

RESULTS

Fluorescence in situ hybridization analysis revealed an expanded phylogenetic gap in NP and CP-off patients relative to FAP. Antibiotic treatment reduced the gap in CP stool. The phylogenetic gap of CP-off patients was due to members of the bacterial families Caulobacteriaceae, Sphingomonadaceae, Comamonadaceae, Peptostreptococcaceae, and Clostridiaceae. There was a greater diversity of phylotypes of Clostridiaceae in CP-off subjects. The phylogenetic gap of NP stool was enriched by Ruminococcaceae and Bifidobacteriaceae. CP stool microbiota had reduced diversity relative to NP and FAP stool due largely to a reduction in Lachnospiraceae/Insertae Sedis XIV/clostridial cluster IV groups.

CONCLUSIONS

Bacterial groups within the expanded phylogenetic gap of pouch patients may have roles in the pathogenesis of pouchitis. Further research concerning the physiology of cultured members of these groups will be necessary to explain their specific roles. Members of the Lachnospiraceae, Incertae Sedis XIV, and clostridial cluster IV could be useful biomarkers of pouch health.

Acute and chronic pouchitis--pathogenesis, diagnosis and treatment

Restorative proctocolectomy with ileal pouch-anal anastomosis has become the procedure of choice for the majority of patients with ulcerative colitis who require surgical treatment. Pouchitis, the most common long-term complication of the procedure, involves a spectrum of disease processes with heterogeneous risk factors, clinical features, disease courses and prognoses. In addition, clinical symptoms of pouchitis are not specific and often overlap with those of other inflammatory and functional pouch disorders, such as Crohn's disease of the pouch and irritable pouch syndrome. Pouchoscopy and biopsy, along with laboratory and radiographic evaluations, are often required for accurate diagnosis in patients with symptoms indicative of pouchitis. Dysbiosis has been implicated as a triggering factor for pouchitis, and concurrent infection with pathogens, such as Clostridium difficile, might contribute to disease relapse and exacerbation. Antibiotic therapy is the main treatment modality. However, the management of antibiotic-dependent and antibiotic-refractory pouchitis remains challenging. Secondary causes of pouchitis, such as ischaemia, NSAID use, the presence of concurrent primary sclerosing cholangitis and other systemic immune-mediated disorders, should be evaluated and properly managed.

Diversity and distribution of sulphate-reducing bacteria in human faeces from healthy subjects and patients with inflammatory bowel disease

The relative abundance of different groups of sulphate-reducing bacteria (SRB) in faecal DNA collected before and after therapy from patients suffering from Crohn's disease (CD), irritable bowel syndrome (IBS) or ulcerative colitis (UC) has been compared with that from healthy controls. Growth tests revealed that SRB were not more abundant in samples from patients with CD before treatment than in the healthy control group. For most of the 128 samples available, these preliminary results were confirmed using degenerate PCR primers that amplify the dsrAB gene. However, some samples from patients with CD before treatment contained a growth inhibitor that was absent from IBS or UC samples. In-depth sequencing of PCR-generated dsrB fragments revealed that the diversity detected was surprisingly low, with only eight strains of SRB and the sulphite-reducing bacterium, Bilophila wadsworthia, detected above the 0.1% threshold. The proportion of the two major species detected, B. wadsworthia and Desulfovibrio piger, was as high as 93.5% of the total SRB population in the healthy control group and lower in all patient groups. Four previously undescribed species were found: it is impossible to predict whether they are sulphate or sulphite-reducing bacteria.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.