Pathogenic mechanisms of postinfectious functional gastrointestinal disorders: results 3 years after gastroenteritis

Emerging role of the gut microbiome in post-infectious irritable bowel syndrome: A literature review

Post-infectious irritable bowel syndrome (PI-IBS) is a particular type of IBS, with symptom onset after an acute episode of infectious gastroenteritis. Despite infectious disease resolution and clearance of the inciting pathogen agent, 10% of patients will develop PI-IBS. In susceptible individuals, the exposure to pathogenic organisms leads to a marked shift in the gut microbiota with prolonged changes in host-microbiota interactions. These changes can affect the gut-brain axis and the visceral sensitivity, disrupting the intestinal barrier, altering neuromuscular function, triggering persistent low inflammation, and sustaining the onset of IBS symptoms. There is no specific treatment strategy for PI-IBS. Different drug classes can be used to treat PI-IBS similar to patients with IBS in general, guided by their clinical symptoms. This review summarizes the current evidence for microbial dysbiosis in PI-IBS and analyzes the available data regarding the role of the microbiome in mediating the central and peripheral dysfunctions that lead to IBS symptoms. It also discusses the current state of evidence on therapies targeting the microbiome in the management of PI-IBS. The results of microbial modulation strategies used in relieving IBS symptomatology are encouraging. Several studies on PI-IBS animal models reported promising results. However, published data that describe the efficacy and safety of microbial targeted therapy in PI-IBS patients are scarce. Future research is required.

The efficacy of vitamin D supplementation for irritable bowel syndrome: a systematic review with meta-analysis

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder involving gut-brain interactions with limited effective treatment options. Vitamin D deficiency is commonly observed in patients with IBS, but whether vitamin D supplementation ameliorates IBS is controversial in randomized controlled trials. The present systematic review and meta-analysis explored the efficacy of vitamin D supplementation in patients with IBS.

METHODS

We performed a systematic search of potentially relevant publications from PubMed, EMBASE, the Cochrane Central Register of Controlled Studies and the Web of Science up until January 2022. We assessed the weighted mean difference (WMD) and 95% confidence interval (95% CI) of the IBS severity scoring system (IBS-SSS), IBS quality of life (IBS-QoL) and IBS total score (IBS-TS) before and after vitamin D supplementation intervention.

RESULTS

We included four randomized, placebo-controlled trials involving 335 participants. The differences in IBS-SSS score between participants in the intervention group and the placebo group increased after intervention (WMD: -55.55, 95% CI: -70.22 to -40.87, I² = 53.7%, after intervention; WMD: -3.17, 95% CI: -18.15 to 11.81, I² = 0.0%, before intervention). Participants receiving vitamin D supplementation showed greater improvement in IBS-SSS after intervention than participants receiving placebo treatment (WMD: -84.21, 95% CI: -111.38 to -57.05, I² = 73.2%; WMD: -28.29, 95% CI: -49.95 to -6.62, I² = 46.6%, respectively). Vitamin D supplementation was also superior to placebo in IBS-QoL improvement (WMD: 14.98, 95% CI: 12.06 to 17.90, I² = 0.0%; WMD: 6.55, 95% CI: -2.23 to 15.33, I² = 82.7%, respectively). Sensitivity analyses revealed an unstable pooled effect on IBS-TS in participants receiving vitamin D supplementation. Therefore, we did not evaluate the efficacy of vitamin D intervention in IBS-TS.

CONCLUSIONS

This systematic review and meta-analysis suggested that vitamin D supplementation was superior to placebo for IBS treatment.

Postinfectious onset in functional dyspepsia is a risk factor for weight loss

BACKGROUND

Functional dyspepsia (FD) is differentiated into two subgroups: the postprandial distress syndrome (PDS) and epigastric pain syndrome (EPS). Acute gastroenteritis and Helicobacter pylori (HP) infection have been identified as risk factors for FD. It is unclear how these risk factors relate to Rome IV subgroups and their clinical impact. We aimed to study the association of postinfectious FD (PI-FD) and HP status with clinical profiles and weight loss.

METHODS

Consecutive FD patients were assessed for symptom frequency and severity. Patients were identified as PDS, EPS or the overlap group according to severity scores. Additionally, PI history and HP status were determined.

RESULTS

In a cohort of 459 FD-patients, 36% were characterized as having PDS, 9% as having EPS and 55% showed overlap. PI onset and positive HP status were reported by, respectively, 20% and 14% of patients, not significantly differing between subgroups (respectively, p = 0.31 and p = 0.40). Weight loss was reported by 63% in PDS, 36% in EPS and 56% in overlap patients (p = 0.011). Only early satiety severity correlated with more severe weight loss in the PDS (r 0.31, p < 0.0001) and overlap group (r 0.38, p < 0.0001). PI-FD patients were more likely to experience weight loss (OR 2.27, p = 0.0013). HP status was not significantly associated with weight loss (p = 0.90).

CONCLUSION

In this cohort, PI onset of FD symptoms emerged as a risk factor for weight loss, but was not associated with the symptom patterns of PDS, EPS or overlap subgroups. Patients with HP infection were not more likely to experience important weight loss.

Intestinal inflammatory profile shows increase in a diversity of biomarkers in irritable bowel syndrome

Background: It has been proposed that irritable bowel syndrome (IBS) is a low-grade mucosal inflammatory disease.Objective: To characterize the intestinal inflammatory profile in IBS patients with or without fructose intolerance.Design: Patients referred to colonoscopy with IBS complaints were screened for participation. IBS patients diagnosed according to the Rome II criteria and with no organic gastrointestinal disease were included in the study. One subgroup was patients included in a fructose-reduced diet study for 2 months with effects based on VAS symptom scores. Healthy controls were subjects under investigation of colorectal cancer screening with no IBS or other gastrointestinal diseases. All patients included had normal histology from rectum. Mucosal cytokines, chemokines and growth factors were measured by multiplex technology.Results: Of 27 inflammatory markers tested in the mucosal tissue, 13 were significantly increased and none was significantly decreased in IBS as compared to controls. Significantly increased were the proinflammatory cytokines tumor necrosis factor, the typical TH1 markers IFNγ, IL-1β, IL-2 and RANTES, the typical TH2 markers IL-5 and IL-9, the TH17 marker IL-17, TNF, the pleiotropic IL-15, and the growth factors bFGF and GM-CSF. In IBS patients with fructose intolerance only IL-5 was significantly increased compared to patients without fructose intolerance.Conclusions: A dysregulated mucosal inflammatory profile with an increased level of TH1, TH2 and TH17 markers, and growth factors were observed in bowel mucosa in of IBS patients when compared to healthy controls.

New insights into irritable bowel syndrome: from pathophysiology to treatment

Irritable bowel syndrome (IBS) is the most common reason to visit a gastroenterologist. IBS was believed to be a functional disease, but many possible pathophysiologic mechanisms can now explain the symptoms. IBS patients are classified into subtypes according to their predominant bowel habit, based on the Rome IV criteria. These include diarrhea-predominant and constipation-predominant IBS, as well as the mixed type, a combination of the two. Usually, IBS treatment is based on the predominant symptoms, with many options for each subtype. A new promising treatment option, fecal microbiota transplantation, seems to have beneficial effects on IBS. However, treating the pathophysiological causative agent responsible for the symptoms is an emerging approach. Therefore, before the appropriate therapeutic option is chosen for treating IBS, a clinical evaluation of its pathophysiology should be performed.

Expression of immune-related genes in rectum and colon descendens of Irritable Bowel Syndrome patients is unrelated to clinical symptoms

BACKGROUND

Mucosal immune activation has been postulated to play an important role in the pathogenesis of irritable bowel syndrome (IBS). However, data are conflicting and often based on small patient cohorts. Here, we aimed to evaluate the gene expression of a large set of immune-related genes in mucosal biopsies from IBS patients and healthy volunteers (HV).

METHODS

A total of 171 IBS patients and 127 HV were included in the study. Rectum biopsies were collected from a cohort of 70 HV and 77 IBS patients (Rome III) and colon descendens biopsies from another cohort of 57 HV and 94 IBS patients (Rome II). Gene expression was assessed using OpenArray technology, and validated questionnaires were used to evaluate clinical characteristics (GI symptoms, somatization, anxiety, and depression).

KEY RESULTS

A subset of IBS patients (33%) with increased immune activation in the colon descendens was identified using multivariate analysis and displayed increased gene expression of IL1B (3-fold change), prostaglandin synthase PTGS2 (2.1-fold change), and the G-protein-coupled receptor MRGPRX2 (10.7-fold change). Clinical characteristics in this subgroup were however similar to the rest of the patient cohort. Analysis of rectal biopsies failed to identify such subgroup of "immuno-active" IBS patients in the other patient cohort.

CONCLUSION

A subset of IBS patients reveals evidence of immune activation in the colon descendens, but not in the rectum; however, gene expression is unrelated to clinical symptoms. To what extent this subgroup might however respond to anti-inflammatory therapy remains to be investigated.

Prospective study evaluating immune-mediated mechanisms and predisposing factors underlying persistent postinfectious abdominal complaints

BACKGROUND

The role of persistent immune activation in postinfectious irritable bowel syndrome (PI-IBS) remains controversial. Here, we prospectively studied healthy subjects traveling to destinations with a high-risk to develop infectious gastroenteritis (IGE) in order to identify immune-mediated mechanisms and risk factors of PI-IBS.

METHODS

One hundred and one travelers were asked to complete questionnaires on psychological profile and gastrointestinal (GI) symptoms before travel, 2 weeks, 6 months and 1 year after travel. At each visit, blood was collected for PBMC isolation and rectal biopsies were taken. PI-IBS was diagnosed using the Rome III criteria and subjects with persistent postinfectious abdominal complaints (PI-AC) were identified using 3 GSRS symptoms (ie, loose stools, urgency and abdominal pain).

RESULTS

Forty-seven of the 101 subjects reported IGE during travel. After 1 year, two subjects were diagnosed with PI-IBS and eight subjects were presented with PI-AC versus two subjects with IBS and two with abdominal complaints in the non-infected group. PBMC analysis showed no differences in T and B cell populations in subjects with PI-AC vs healthy. Additionally, no differences in gene expression were observed in the early postinfectious phase or after 1 year. Regression analysis identified looser stools, higher anxiety and somatization before infection and several postinfectious GI symptoms as risk factors for PI-AC.

CONCLUSIONS

The incidence of PI-IBS is low following travelers' diarrhea and there is need for larger studies investigating the role of immune activation in PI-IBS. Psychological factors before infection and the severity of symptoms shortly after infection are risk factors for the persistence of PI-AC.

Pathophysiology of Functional Gastrointestinal Disorders: A Holistic Overview

Background and Summary: Traditionally, functional gastrointestinal disorders (FGID), including functional dyspepsia or irritable bowel syndrome (IBS), are defined by more or less specific symptoms and the absence of structural or biochemical abnormalities that cause these symptoms. This concept is now considered to be outdated; if appropriate tests are applied, structural or biochemical abnormalities that explain or cause the symptoms may be found in many patients. Another feature of FGID are the highly prevalent psychiatric comorbidities, such as depression and anxiety. It is implied that mood disorders "cause" gastrointestinal symptoms. In fact, epidemiological data now provide strong evidence that in subsets of cases, gastrointestinal (GI) symptoms arise first and mood disorders occur later, while in other patients the reverse appears to happen. Possible mechanisms for gut-brain dysfunction have been identified, with systemic minimal inflammation as a causal factor in at least some subjects. Other mechanisms that play a role in FGID include chronic infections, intestinal microbiota, low-grade mucosal inflammation including the increase of eosinophils, systemic immune activation, altered intestinal permeability, in diarrhea predominant IBS altered bile salt metabolism, abnormalities in the serotonin metabolism and genetic factors. All these factors might be modulated by environmental factors such as diet. Key Messages: While a number of factors can be linked to specific symptoms (e.g., pain or diarrhea), it is evident that the symptom-based categorization of patients will not allow targeted treatments that specifically address the underlying pathophysiology.

Evidence for long-term sensitization of the bowel in patients with post-infectious-IBS

Post-infectious irritable bowel syndrome (PI-IBS) is a common gastrointestinal disorder characterized by persistent abdominal pain despite recovery from acute gastroenteritis. The underlying mechanisms are unclear, although long-term changes in neuronal function, and low grade inflammation of the bowel have been hypothesized. We investigated the presence and mechanism of neuronal sensitization in a unique cohort of individuals who developed PI-IBS following exposure to contaminated drinking water 7 years ago. We provide direct evidence of ongoing sensitization of neuronal signaling in the bowel of patients with PI-IBS. These changes occur in the absence of any detectable tissue inflammation, and instead appear to be driven by pro-nociceptive changes in the gut micro-environment. This is evidenced by the activation of murine colonic afferents, and sensitization responses to capsaicin in dorsal root ganglia (DRGs) following application of supernatants generated from tissue biopsy of patients with PI-IBS. We demonstrate that neuronal signaling within the bowel of PI-IBS patients is sensitized 2 years after the initial infection has resolved. This sensitization appears to be mediated by a persistent pro-nociceptive change in the gut micro-environment, that has the capacity to stimulate visceral afferents and facilitate neuronal TRPV1 signaling.

Post-Infectious Irritable Bowel Syndrome

PURPOSE OF REVIEW

Post-infectious irritable bowel syndrome (PI-IBS) is characterized by persistent abdominal pain and diarrhea, typically following an episode of infectious gastroenteritis. The mechanisms that underlie IBS-D remain elusive, but PI-IBS provides a mechanistic model of this disorder. This review provides an up-to-date appraisal of the pathophysiology, clinical features, and management approaches for PI-IBS.

RECENT FINDINGS

Disordered immune reactions and release of cytokines with resultant gut inflammation and dysfunction appear to be key features of PI-IBS. Disordered brain-gut-microbiota interactions, type of infecting agent, and host-genetic susceptibility are risk factors but also are reasons for the varying spectrum of clinical severity. Although prognosis is generally good, symptoms and inflammation may persist for a long time. Symptomatic relief with antidiarrheals, antispasmodics, 5HT₃ antagonists, mesalamine, probiotics, and low-dose antidepressants remain the primary approaches, but in some difficult cases, a combination of drugs that target the pathophysiology may be helpful. PI-IBS has many overlapping features with IBS-D and shares similar pathophysiology and management approaches.

Neuroimmune factors in functional gastrointestinal disorders: A focus on irritable bowel syndrome

BACKGROUND

Abnormal abdominal pain perception is the most bothersome and difficult to treat symptom of functional gastrointestinal disorders (FGIDs). Visceral pain stimuli are perceived and transmitted by afferent neurons residing in the dorsal root ganglia that have sensory nerve endings in the gut wall and mesentery. Accumulating evidence indicates that peripheral activation and sensitization of these sensory nerve endings by bioactive mediators released by activated immune cells, in particular mast cells, can lead to aberrant neuroimmune interactions and the development and maintenance of visceral hypersensitivity. Besides direct neuronal activation, low concentrations of proteases, histamine, and serotonin can chronically sensitize nociceptors, such as TRP channels, leading to persistent aberrant pain perception.

PURPOSE

This review discusses the potential mechanisms underlying aberrant neuroimmune interactions in peripheral sensitization of sensory nerves. A better understanding of the cells, mediators, and molecular mechanisms triggering persistent aberrant neuroimmune interactions brings new insights into their contribution to the physiology and pathophysiology of visceral pain perception and provides novel opportunities for more efficient therapeutic treatments for these disorders.

Psychological comorbidity increases the risk for postinfectious IBS partly by enhanced susceptibility to develop infectious gastroenteritis

OBJECTIVE

Psychological factors increase the risk to develop postinfectious IBS (PI-IBS), but the mechanisms involved are unclear. As stress affects the immune system, we investigated the potential interaction between psychological factors, the immune response against infectious gastroenteritis (IGE) and the development of IGE and PI-IBS in a large cohort exposed to contaminated drinking water.

DESIGN

18 620 people exposed to contaminated drinking water (norovirus, Giardia lamblia, Campylobacter jejuni) were invited to participate in a prospective controlled cohort study. They were asked to complete questionnaires assessing demographic, psychological and clinical data during the outbreak and 1 year later. At both time points, in-depth immune function (peripheral blood and rectal biopsies) was studied in a subgroup of subjects.

RESULTS

1379 subjects completed the questionnaires during the outbreak, of which 271 developed IGE. Risk factors for IGE included younger age, pre-existing dyspepsia-like symptoms, anxiety and drinking contaminated tap water. Anxiety scores before the outbreak inversely correlated with interleukin-2-expressing CD4+ T cells (r=0.6, p=0.01, n=23). At follow-up, 34 of 172 (20%) IGE subjects developed IBS compared with 24/366 exposed participants (7%, p<0.0001, χ(2) test). A Th2 cytokine phenotype at time of infection was associated with increased risk for PI-IBS 1 year later. Except for increased B cell numbers, no evidence for systemic or rectal mucosal immune activation in PI-IBS was demonstrated at follow-up.

CONCLUSIONS

Our study shows that the increased risk of patients with psychological comorbidity to develop PI-IBS may partly result from an increased susceptibility to develop IGE, possibly resulting from a Th2-immune bias.

TRIAL REGISTRATION NUMBER

(ClinicalTrials.gov NCT01497847).

Smoking is associated with several functional gastrointestinal symptoms

BACKGROUND

The etiology behind functional gastrointestinal symptoms is not clear. Only a few studies have examined how lifestyle factors affect these symptoms, especially in middle-aged or elder subjects. The aim of the present study was to describe the prevalence of functional gastrointestinal symptoms in a Swedish population-based cohort of middle-aged to elder subjects, and to examine associations between symptoms and smoking and alcohol use.

METHODS AND MATERIALS

This study was conducted on a web-based baseline questionnaire from a part of the EpiHealth study. The cohort included 16,840 subjects between 45 and 75 years of age. Subjects with organic gastrointestinal diseases were excluded. Gastrointestinal symptoms were defined as functional abdominal pain, functional bloating, functional constipation, and functional diarrhea. Parameters regarding age, gender, educational level, occupation, civil status, physical activity, and body mass index (BMI) were described, and association between smoking and alcohol habits were calculated, adjusted for parameters with >5 percentage difference between cases and controls.

RESULTS

An association was found between former and current smoking and functional abdominal pain (OR: 1.15, 95% CI: 1.03-1.28 vs. OR: 1.30, 95% CI: 1.08-1.57). Former smoking was associated with functional bloating (OR: 1.18, 95% CI: 1.04-1.33) and functional constipation (OR: 1.28, 95% CI: 1.06-1.56). There was a trend of decreased functional abdominal pain, functional constipation, and functional diarrhea in subjects with a moderate alcohol intake.

CONCLUSION

Smoking is associated with functional abdominal pain, functional bloating, and functional constipation. A moderate alcohol intake tends to be associated with decreased risk of functional gastrointestinal symptoms.

Prevalence of Functional Gastrointestinal Disorders in Schoolchildren in Ecuador

The prevalence of functional gastrointestinal disorders (FGIDs) in children in Ecuador is unknown. We describe a survey study in 2 schools in Quito, Ecuador, using a Spanish translation of the Questionnaire on Pediatric Gastrointestinal Symptoms-Rome III Version (QPGS-RIII). A total of 417 children (51% boys) with a mean age of 12.0 years were included. FGIDs were present in 95 children (22.8%) and occurred in 25% of girls and in 20.7% of boys (P = 0.296). Functional defecation disorders were found in 12.0% of children, 9.4% had an abdominal pain-related FGID and 3.8% was diagnosed with a vomiting or aerophagia FGID.

ACG Clinical Guideline: Diagnosis, Treatment, and Prevention of Acute Diarrheal Infections in Adults

Acute diarrheal infections are a common health problem globally and among both individuals in the United States and traveling to developing world countries. Multiple modalities including antibiotic and non-antibiotic therapies have been used to address these common infections. Information on treatment, prevention, diagnostics, and the consequences of acute diarrhea infection has emerged and helps to inform clinical management. In this ACG Clinical Guideline, the authors present an evidence-based approach to diagnosis, prevention, and treatment of acute diarrhea infection in both US-based and travel settings.

Increased risk of functional gastrointestinal sequelae after Clostridium difficile infection among active duty United States military personnel (1998-2010)

BACKGROUND & AIMS

Some acute enteric infections are associated with the development of functional gastrointestinal disorders, most commonly irritable bowel syndrome but also other functional and organic gastrointestinal sequelae. Clostridium difficile infection has increased in incidence and severity, however, few studies have evaluated functional disorders after this infection.

METHODS

We evaluated the epidemiology and sequelae of C difficile in the US military population by using the US Department of Defense's Armed Forces Health Surveillance Center Defense Medical Ecounter Database. We then performed a retrospective cohort study of 891 active-duty US military personnel who developed C difficile from 1998 to 2010 and 3231 matched subjects who had not been exposed to C difficile. Subjects were identified based on International Classification of Diseases, 9th revision, Clinical Modification codes for C difficile disease.

RESULTS

C difficile was associated independently with increased rate ratios (RRs) for incident irritable bowel syndrome (RR, 6.1; 95% confidence interval [CI], 2.9-12.9), gastroesophageal reflux disease (GERD) (RR, 1.9; 95% CI, 1.4-2.6), dyspepsia (RR, 3.3; 95%, 1.4-7.7), and constipation (RR, 2.2; 95% CI, 1.3-3.7). Approximately 14.1% of subjects with C difficile later were identified with one of these functional gastrointestinal disorders (FGDs), compared with 6% of controls. Community- and health care-associated C difficile were associated at similar rates with these sequelae. Patients were at increased risk for FGDs within 3 months of a C difficile episode, with one additional case of FGD developing for every 12 diagnoses of C difficile.

CONCLUSIONS

The incidence of community- and health care-associated C difficile has increased in the US military population from 1998 through 2010. As for other gastrointestinal infections, C difficile disease is associated with clinically relevant functional sequelae in this military population.

Immunological Biomarkers in Postinfectious Irritable Bowel Syndrome

BACKGROUND

There is a recognized need for biological markers to facilitate diagnoses of irritable bowel syndrome (IBS) and to distinguish it from other functional and organic disorders. As postinfectious IBS (PI-IBS) is believed to account for as many as one third of all IBS cases, here we sought to identify differences in specific cytokines and serologic responses across patients with idiopathic IBS and PI-IBS and healthy controls.

METHODS

At total of 120 US military personnel were identified from the Defense Medical Surveillance System-based International Classification of Diseases, 9th Revision, Clinical Modification (ICD9-CM) codes recorded during medical encounters and were grouped based on infectious gastroenteritis (IGE) episode (Shigella, Campylobacter, Salmonella, or an unspecified pathogen) followed by IBS, IBS without antecedent IGE, or IGE without subsequent IBS within 2 years of the IGE exposure. Sera from subjects were assayed for cytokine levels and antibodies against a panel of microbiome antigens.

RESULTS

In total, 10 of 118 markers considered were shown to differ between IBS patients and healthy controls, including cytokines interleukin-6 (IL-6), IL-8, IL-1β, and macrophage inflammatory protein-1β (MIP-1β), as well as antibody responses to microbial antigens. Antimicrobial antibody response profiles also differed between PI-IBS cases compared with IBS cases without an antecedent episode of acute IGE. Comparisons also suggest that immunoglobulin A (IgA) and IgG profiles may point to pathogen-specific origins among PI-IBS cases.

CONCLUSION

Taken together, these results provide further evidence as to the molecular distinctness of classes of IBS cases and that serum biomarkers may prove useful in elucidating their pathobiological pathways.

Predictive factors for the diagnosis of irritable bowel syndrome in a large cohort of 440,822 young adults

BACKGROUND

The prevalence of irritable bowel syndrome (IBS) in the community has been reported in numerous cross-sectional surveys. However, little is known about the incidence and predictive factors for the clinical diagnosis of IBS.

METHODS

We examined the association of socioeconomic, anthropometric, and occupational factors with the incidence of IBS in a cohort of 440,822 young Israeli adults aged 18 to 39 who served in active military service during the years 2005 to 2011.

RESULTS

During the follow-up of 1,925,003 person-years, IBS was diagnosed de novo in 976 patients, giving an incidence rate of 221:100,000 (0.2%) person-years for the diagnosis of IBS. On multivariable Cox analysis, higher socioeconomic status [hazard ratio (HR) 1.629; 95% confidence interval (CI), 1.328-1.999; P<0.0001], Israeli birth (HR 1.362; 95% CI, 1.084-1.712; P=0.008), Jewish ethnicity (HR 2.089; 95% CI, 1.344-3.248; P=0.001), education ≥than 11 years (HR 1.674; 95% CI, 1.019-2.751; P=0.042), and a noncombat military position (HR 1.196; 95% CI, 1.024-1.397; P=0.024) were found to be risk factors for the diagnosis or for the worsening of IBS. Overweight (HR 0.744; 95% CI, 0.589-0.941; P=0.014), obesity (HR 0.698; 95% CI, 0.510-0.95; P=0.025), living in a rural settlement (HR 0.705; 95% CI, 0.561-0.886; P=0.003), and Middle Eastern (HR 0.739; 95% CI, 0.617-0.884; P=0.001,) or North African and Ethiopian origin (HR 0.702; 95% CI, 0.585-0.842; P<0.001) were found to be protective for the diagnosis or the worsening of IBS.

CONCLUSIONS

This study provides novel data on the socioeconomic, anthropometric, and occupational factors predictive for IBS development. The predictive factors for IBS diagnosis may point to the fact that stress had a lower impact on IBS incidence in our study cohort.

Early life events predispose the onset of childhood functional gastrointestinal disorders

BACKGROUND

Functional gastrointestinal disorders (FGIDs) are common digestive conditions characterized by chronic or recurrent symptoms in the absence of a clearly recognized gastrointestinal etiology. The biopsychosocial model, the most accepted concept explaining chronic pain conditions, proposes that the interplay of multiple factors such as genetic susceptibility, early life experiences, sociocultural issues, and coping mechanisms affect children at different stages of their lives leading to the development of different pain phenotypes and pain behaviors. Early life events including gastrointestinal inflammation, trauma, and stress may result in maladaptive responses that could lead to the development of chronic pain conditions such as FGIDs.

AIMS

In this review, we discuss novel findings from studies regarding the long-term effect of early life events and their relationship with childhood chronic abdominal pain and FGIDs.

METHODS

A bibliographic search of the PubMed database was conducted for articles published over the last 20 years using the keywords: "Functional gastrointestinal disorders", "chronic abdominal pain", "chronic pain", "gastrointestinal inflammation", and "early life events". Forty-three articles were chosen for review.

RESULTS

Based on the current evidence, events that take place early in life predispose children to the development of chronic abdominal pain and FGIDs. Conditions that have been studied include cow's milk protein hypersensitivity, pyloric stenosis, gastrointestinal infections, and Henoch-Schonlein purpura, among others.

CONCLUSIONS

Early events may play an important role in the complex pathogenesis of functional gastrointestinal conditions. Timely intervention may have a critical impact on the prevention of this group of chronic incapacitating conditions.

Pathogen-specific risk of chronic gastrointestinal disorders following bacterial causes of foodborne illness

Background

The US CDC estimates over 2 million foodborne illnesses are annually caused by 4 major enteropathogens: non-typhoid Salmonella spp., Campylobacter spp., Shigella spp. and Yersinia enterocoltica. While data suggest a number of costly and morbid chronic sequelae associated with these infections, pathogen-specific risk estimates are lacking. We utilized a US Department of Defense medical encounter database to evaluate the risk of several gastrointestinal disorders following select foodborne infections.

Methods

We identified subjects with acute gastroenteritis between 1998 to 2009 attributed to Salmonella (nontyphoidal) spp., Shigella spp., Campylobacter spp. or Yersinia enterocolitica and matched each with up to 4 unexposed subjects. Medical history was analyzed for the duration of military service time (or a minimum of 1 year) to assess for incident chronic gastrointestinal disorders. Relative risks were calculated using modified Poisson regression while controlling for the effect of covariates.

Results

A total of 1,753 pathogen-specific gastroenteritis cases (Campylobacter: 738, Salmonella: 624, Shigella: 376, Yersinia: 17) were identified and followed for a median of 3.8 years. The incidence (per 100,000 person-years) of PI sequelae among exposed was as follows: irritable bowel syndrome (IBS), 3.0; dyspepsia, 1.8; constipation, 3.9; gastroesophageal reflux disease (GERD), 9.7. In multivariate analyses, we found pathogen-specific increased risk of IBS, dyspepsia, constipation and GERD.

Conclusions

These data confirm previous studies demonstrating risk of chronic gastrointestinal sequelae following bacterial enteric infections and highlight additional preventable burden of disease which may inform better food security policies and practices, and prompt further research into pathogenic mechanisms.

In Vivo and In Vitro Antinociceptive Effect of Fagopyrum cymosum (Trev.) Meisn Extracts: A Possible Action by Recovering Intestinal Barrier Dysfunction

Fagopyrum cymosum (Trev.) Meisn (Fag) is a herb rhizome which has been widely used to treat diseases. To investigate the effects and mechanisms of the Fag on irritable bowel syndrome (IBS), in vivo neonatal pups maternal separation (NMS) combined with intracolonic infusion of acetic acid (AA) was employed to establish IBS rat models. Fag reduced their visceral hyperalgesia and the whole gut permeability, ameliorated colonic mucosa inflammation and injury, and upregulated the expression of decreased tight junction proteins (TJs) of claudin-1, occludin, and ZO-1 (except ZO-2) in colonic epithelium. Caco-2 monolayer cells were incubated with TNF-α and IFN-γ   in vitro to establish an epithelial barrier dysfunction model whose transepithelial electrical resistance (TER) depended more on dose of Fag than that of the controls, and whose TJs levels were lower than those of the controls. Fag upregulated the NP-40 insoluble and soluble components of the four TJs markedly in a dose-dependent manner. These data suggest that Fag alleviated the hyperalgesia of IBS rats by reducing intestinal inflammation and enhancing mucosal epithelial function after regulating the structure and function of TJs.

Diarrhoea during military deployment: current concepts and future directions

PURPOSE OF REVIEW

Diarrhoea among military travellers deployed globally in conflict and peacekeeping activities remains one of the most important health threats. Here we review recent advances in our understanding of the epidemiology, laboratory identification, treatment and chronic health consequences of this multi-cause infection, and consider the implications for public health management and future research.

RECENT FINDINGS

The incidence of diarrhoea among deployed military personnel from industrialized countries to lesser developed countries is approximately 30% per month overall, with clinical incidence between 5 and 7% per 100 person-months. The risk appears to be higher early during deployment and is associated with poor hygienic conditions and contaminated food sources. Gaps remain in our understanding of the cause, given the lack of laboratory capability in austere conditions of deployment; however, recent advances in molecular methods of characterization hold promise in improving our detection capabilities. While there have been improvements in understanding of best treatments, more work needs to be done in transforming this knowledge into action and optimizing single-dose antibiotic treatment regimens. Finally, the under-recognized burden of chronic consequences of these infections is gaining awareness and reinforces the need to find effective preventive strategies.

SUMMARY

Our understanding of the epidemiology of diarrhoea is improving but further research is needed to fully account for acute operational-focused health impacts as well as the chronic enduring disease impacts. Improved field diagnostics would be of great value to support these efforts.

Experimental endotoxemia as a model to study neuroimmune mechanisms in human visceral pain

The administration of bacterial endotoxin (i.e., lipopolysaccharide, LPS) constitutes a well-established experimental approach to study the effects of an acute and transient immune activation on physiological, behavioral, and emotional aspects of sickness behavior in animals and healthy humans. However, little is known about possible effects of experimental endotoxemia on pain in humans. This knowledge gap is particularly striking in the context of visceral pain in functional as well as chronic-inflammatory gastrointestinal disorders. Although inflammatory processes have been implicated in the pathophysiology of visceral pain, it remains incompletely understood how inflammatory mediators interact with bottom-up (i.e., increased afferent input) and top-down (i.e., altered central pain processing) mechanisms of visceral hyperalgesia. Considering the recent findings of visceral hyperalgesia after LPS application in humans, in this review, we propose that experimental endotoxemia with its complex peripheral and central effects constitutes an experimental model to study neuroimmune communication in human pain research. We summarize and attempt to integrate relevant animal and human studies concerning neuroimmune communication in visceral and somatic pain, discuss putative mechanisms, and conclude with future research directions.

An Update on Post-infectious Irritable Bowel Syndrome: Role of Genetics, Immune Activation, Serotonin and Altered Microbiome

The literature on post-infectious irritable bowel syndrome (IBS) is reviewed with special emphasis on recent new data. Further accounts of this phenomenon continue to be reported following a range of infections including giardiasis as well as viral and bacterial gastroenteritis. Risk factors such as severity of initial illness, female gender together with adverse psychological factors have been confirmed. Recent evidence of a genetic predisposition needs replication. Animal studies suggest activation of mast cells and inflammation driven impairment of serotonin transporter may be important, which are findings supported by some recent human studies in IBS with diarrhoea. Experimentally induced inflammation leads to damage and remodelling of enteric nerves. Similar changes have been reported in IBS patients with increase in nerves expressing transient receptor potential cation channel V1. While changes in microbiota are very likely this area has yet to be explored using modern techniques. Since the prognosis is for slow improvement, treatments should currently target the key symptoms of diarrhoea and abdominal pain. Future therapies aimed at correcting underlying mechanisms including immune activation and serotonin excess are currently being explored and may provide better treatments in the future.

Global prevalence of and risk factors for irritable bowel syndrome: a meta-analysis

BACKGROUND & AIMS

Many cross-sectional surveys have reported the prevalence of irritable bowel syndrome (IBS), but there have been no recent systematic review of data from all studies to determine its global prevalence and risk factors.

METHODS

MEDLINE, EMBASE, and EMBASE Classic were searched (until October 2011) to identify population-based studies that reported the prevalence of IBS in adults (≥15 years old); IBS was defined by using specific symptom-based criteria or questionnaires. The prevalence of IBS was extracted for all studies and based on the criteria used to define it. Pooled prevalence, according to study location and certain other characteristics, odds ratios (ORs), and 95% confidence intervals (CIs) were calculated.

RESULTS

Of the 390 citations evaluated, 81 reported the prevalence of IBS in 80 separate study populations containing 260,960 subjects. Pooled prevalence in all studies was 11.2% (95% CI, 9.8%-12.8%). The prevalence varied according to country (from 1.1% to 45.0%) and criteria used to define IBS. The greatest prevalence values were calculated when ≥3 Manning criteria were used (14%; 95% CI, 10.0%-17.0%); by using the Rome I and Rome II criteria, prevalence values were 8.8% (95% CI, 6.8%-11.2%) and 9.4% (95% CI, 7.8%-11.1%), respectively. The prevalence was higher for women than men (OR, 1.67; 95% CI, 1.53-1.82) and lower for individuals older than 50 years, compared with those younger than 50 (OR, 0.75; 95% CI, 0.62-0.92). There was no effect of socioeconomic status, but only 4 studies reported these data.

CONCLUSIONS

The prevalence of IBS varies among countries, as well as criteria used to define its presence. Women are at slightly higher risk for IBS than men. The effects of socioeconomic status have not been well described.

Incidence of post-infectious irritable bowel syndrome and functional intestinal disorders following a water-borne viral gastroenteritis outbreak

OBJECTIVES

Post-infectious irritable bowel syndrome (PI-IBS) may develop in 4-31% of affected patients following bacterial gastroenteritis (GE), but limited information is available on long-term outcome of viral GE. During summer 2009, a massive outbreak of viral GE associated with contamination of municipal drinking water (Norovirus) occurred in San Felice del Benaco (Lake Garda, Italy). To investigate the natural history of a community outbreak of viral GE, and to assess the incidence of PI-IBS and functional gastrointestinal disorders, we carried out a prospective population-based cohort study with a control group.

METHODS

Baseline questionnaires were administered to the resident community within 1 month of the outbreak. Follow-up questionnaires of the Italian version of Gastrointestinal Symptom Rating Scale (GSRS, a 15-item survey scored according to a 7-point Likert scale) were mailed to all patients responding to baseline questionnaire at 3 and 6 months, and to a cohort of unaffected controls, living in the same geographical area, at 6 months after the outbreak. The GSRS item were grouped in five dimensions: abdominal pain, reflux, indigestion, diarrhea, and constipation. At month 12, all patients and controls were interviewed by a health assistant to verify Rome III criteria of IBS. Student's t-test and χ(2)- or Fisher's exact test were used as appropriate.

RESULTS

Baseline questionnaires were returned by 348 patients: mean age ± s.d. 45 ± 22 years, 53% female. At outbreak, nausea (scored ≥4), vomiting, and diarrhea lasting 2-3 days or more were reported by 66, 60, and 77% of patients, respectively. A total of 50% reported fever and 19% reported weight loss (mean 3 kg). Follow-up surveys were returned at month 6 by 186 patients and 198 controls: mean GSRS score was significantly higher in patients than in controls for abdominal pain, diarrhea, and constipation. At month 12, we identified 40 patients with a new diagnosis of IBS (Rome III criteria), in comparison with 3 subjects in the control cohort (P<0.0001; odds ratio 11.40; 95% confidence intervals 3.44-37.82). The 40 cases of PI-IBS were subtyped according to the predominant stool pattern as follows: 4 IBS with constipation, 7 IBS with diarrhea, 16 with mixed IBS, and 13 with unsubtyped IBS.

CONCLUSIONS

Our study provides evidence that Norovirus GE leads to the development of PI-IBS in a substantial proportion of patients (13%), similar to that reported after bacterial GE.

Patients with irritable bowel syndrome and dysmotility express antibodies against gonadotropin-releasing hormone in serum

BACKGROUND

The etiology of irritable bowel syndrome (IBS) and dysmotility is in most cases unknown. Organic, pathognomonic changes have not been described. We have previously demonstrated sporadic expressions of antibodies against gonadotropin-releasing hormone (GnRH) in serum from these patients. The aim of this study was to screen for the presence of GnRH antibodies in healthy subjects and patients with gastrointestinal (GI) diseases.

METHODS

Consecutive patients suffering from either IBS, idiopathic dysmotility, GI complaints secondary to diabetes mellitus, celiac disease or inflammatory bowel disease (IBD) were included. Healthy blood donors served as controls. Blood samples were taken for analyzing IgM and IgG antibodies against GnRH using an ELISA method. Medical records were scrutinized with respect to duration of symptoms, co-existing diseases, drug treatments, hereditary factors, and laboratory analyses.

KEY RESULTS

Healthy controls expressed low levels of GnRH IgM antibodies in a prevalence of 23%. The prevalence of GnRH IgM antibodies in IBS and dysmotility patients was 42% (P = 0.008), and the levels were higher (P = 0.000). Patients with diabetes mellitus expressed GnRH IgM antibodies in the same prevalence as controls (25%), but in higher levels (P = 0.02). Patients with celiac disease or IBD had the same or lower levels of antibodies. There were no associations between antibodies, other co-existing diseases or laboratory analyses.

CONCLUSIONS & INFERENCES

Higher levels of GnRH IgM antibodies were detected in patients with IBS and dysmotility, but not organic GI diseases, compared with healthy controls. These findings suggest that IBS and dysmotility to some extent may be of an autoimmune origin.

[Post-infectious functional gastrointestinal disorders: from the acute episode to chronicity]

Functional gastrointestinal disorders (FGID) form a major part of gastroenterology practice. Several studies have reported the development of post-infectious irritable bowel syndrome (PI-IBS) after acute gastroenteritis (AGE). Non-gastrointestinal (GI) infections may increase the risk of developing IBS. There are also data showing that a GI infection may trigger functional dyspepsia (PI-FD). The possible development of PI-IBS or PI-FD depends on factors related to both the infection and the host. Microinflammation has been found in patients with post-infectious FGID. Studies performed in animal models show that infection and acute inflammation permanently change gastrointestinal motility and sensitivity. The role of AGE in the development of FGID is important not only because this entity provides an excellent natural model for pathogenic study but also because it provides an opportunity for preventive action.

Mucosal inflammation as a potential etiological factor in irritable bowel syndrome: a systematic review

BACKGROUND

The causes of irritable bowel syndrome (IBS) remain obscure. Some investigators have proposed chronic low-grade mucosal inflammation as a potential etiological factor. We performed a systematic review to examine this issue in detail.

METHODS

MEDLINE, EMBASE, and EMBASE classic were searched up to December 2010 to identify studies of case-control design applying tests for low-grade inflammation to either full-thickness intestinal or endoscopic mucosal biopsies from patients with IBS. Controls were required to be healthy individuals, or asymptomatic patients undergoing investigation for reasons other than the reporting of upper or lower gastrointestinal symptoms. Individual study results were summarized descriptively.

RESULTS

The literature search identified 1388 citations, of which 16 studies were eligible for inclusion. Individual study results were diverse, partly as a consequence of the different surrogate markers for inflammatory mechanisms studied. Mast cells, T lymphocytes, B lymphocytes, and mucosal cytokine production all appeared altered among cases with IBS in individual studies, while no study demonstrated a significant difference in numbers of plasma cells, neutrophils, or eosinophils. Some studies suggested a relationship between mast cell abnormalities and symptom severity and frequency, as well as co-existent fatigue and depression. Studies were limited by the lack of comparability of controls, and the fact that most were conducted in highly selected groups of patients with IBS.

CONCLUSIONS

Low-grade mucosal inflammation, particularly mast cell activation, may be a contributory factor in the pathogenesis of IBS. Mast cell stabilizers warrant further assessment as a potential therapy in the condition.

The Incidence and gastrointestinal infectious risk of functional gastrointestinal disorders in a healthy US adult population

OBJECTIVES

Functional gastrointestinal disorders (FGDs) are recognized sequelae of infectious gastroenteritis (IGE). Within the active duty military population, a group with known high IGE rates, the population-based incidence, risk factors, and attributable burden of care referable to FGD after IGE are poorly defined.

METHODS

Using electronic medical encounter data (1999-2007) on active duty US military, a matched, case-control study describing the epidemiology and risk determinants of FGD (irritable bowel syndrome (IBS), functional constipation (FC), functional diarrhea (FD), dyspepsia (D)) was conducted. Incidence rates and duration of FGD-related medical care were estimated, and conditional logistic regression was utilized to evaluate FGD risk after IGE.

RESULTS

A total of 31,866 cases of FGD identified were distributed as follows: FC 55% (n=17,538), D 21.2% (n=6,750), FD 2.1% (n=674), IBS 28.5% (n=9,091). Previous IGE episodes were distributed as follows: specific bacterial pathogen (n=65, 1.2%), bacterial, with no pathogen specified (n=2155, 38.9%), protozoal (n=38, 0.7%), viral (n=3431, 61.9%). A significant association between IGE and all FGD (odds ratio (OR) 2.64; P<0.001) was seen, with highest risk for FD (OR 6.28, P<0.001) and IBS (OR 3.72, P<0.001), and moderate risk for FC (2.15, P<0.001) and D (OR 2.39, P<0.001). Risk generally increased with temporal proximity to, and bacterial etiology of, exposure. Duration of FGD-related care was prolonged with 22.7% having FGD-associated medical encounters 5 years after diagnosis.

CONCLUSIONS

FGD are common in this population at high risk for IGE. When considering effective countermeasures and mitigation strategies, attention directed toward prevention as well as the acute and chronic sequelae of these infections is needed.

Prevalence of uninvestigated dyspepsia 8 years after a large waterborne outbreak of bacterial dysentery: a cohort study

BACKGROUND & AIMS

Symptoms of dyspepsia may occur following an episode of acute gastroenteritis, but data are conflicting. We assessed prevalence of uninvestigated dyspepsia in a cohort of individuals, some of whom were exposed to bacterial dysentery in May 2000, as well as risk factors for dyspepsia in exposed individuals.

METHODS

This was a cohort study conducted in the town of Walkerton, Ontario, Canada. Involved individuals were recruited into the Walkerton Health Study between 2002 and 2003 and were attending for annual assessment in 2008. Exposed individuals were subdivided into those with self-reported gastroenteritis, with acute illness unconfirmed by health records, and those with clinically confirmed gastroenteritis, with substantiation of acute illness by health record review. Presence of dyspepsia at 8 years, according to a broad definition (any symptom referable to the upper gastrointestinal tract), and the Rome II criteria, was compared between exposed and nonexposed individuals.

RESULTS

Of 2597 subjects eligible, 1088 (41.9%) provided data for analysis, and 706 (64.9%) had reported acute gastroenteritis. Multivariate odd ratios for dyspepsia at 8 years in exposed individuals using a broad definition and the Rome II definition were 2.09 (95% confidence interval: 1.58-2.78) and 2.30 (95% confidence interval: 1.63-3.26), respectively. Prevalence of dyspepsia was higher in females; smokers; those with premorbid irritable bowel syndrome, anxiety, or depression; and those reporting >7 days of diarrhea or abdominal cramps during the acute illness.

CONCLUSIONS

Symptoms of dyspepsia 8 years after an outbreak of acute gastroenteritis were significantly more prevalent in exposed compared with nonexposed individuals.