Post-infectious irritable bowel syndrome

Multi-Cell-Type Openness-Weighted Association Studies for Trait-Associated Genomic Segments Prioritization

Openness-weighted association study (OWAS) is a method that leverages the in silico prediction of chromatin accessibility to prioritize genome-wide association studies (GWAS) signals, and can provide novel insights into the roles of non-coding variants in complex diseases. A prerequisite to apply OWAS is to choose a trait-related cell type beforehand. However, for most complex traits, the trait-relevant cell types remain elusive. In addition, many complex traits involve multiple related cell types. To address these issues, we develop OWAS-joint, an efficient framework that aggregates predicted chromatin accessibility across multiple cell types, to prioritize disease-associated genomic segments. In simulation studies, we demonstrate that OWAS-joint achieves a greater statistical power compared to OWAS. Moreover, the heritability explained by OWAS-joint segments is higher than or comparable to OWAS segments. OWAS-joint segments also have high replication rates in independent replication cohorts. Applying the method to six complex human traits, we demonstrate the advantages of OWAS-joint over a single-cell-type OWAS approach. We highlight that OWAS-joint enhances the biological interpretation of disease mechanisms, especially for non-coding regions.

Copper toxicity towards Campylobacter jejuni is enhanced by the nickel chelator dimethylglyoxime

The nickel (Ni)-chelator dimethylglyoxime (DMG) was found to be bacteriostatic towards Campylobacter jejuni. Supplementation of nickel to DMG-containing media restored bacterial growth, whereas supplementation of cobalt or zinc had no effect on the growth inhibition. Unexpectedly, the combination of millimolar levels of DMG with micromolar levels of copper (Cu) was bactericidal, an effect not seen in select Gram-negative pathogenic bacteria. Both the cytoplasmic Ni-binding chaperone SlyD and the twin arginine translocation (Tat)-dependent periplasmic copper oxidase CueO were found to play a central role in the Cu-DMG hypersensitivity phenotype. Ni-replete SlyD is needed for Tat-dependent CueO translocation to the periplasm, whereas Ni-depleted (DMG-treated) SlyD is unable to interact with the CueO Tat signal peptide, leading to mislocalization of CueO and increased copper sensitivity. In support of this model, C. jejuni ΔslyD and ΔcueO mutants were more sensitive to copper than the wild-type (WT); CueO was less abundant in the periplasmic fraction of ΔslyD or DMG-grown WT cells, compared to WT cells grown on plain medium; SlyD binds the CueO signal sequence peptide, with DMG inhibiting and nickel enhancing the binding, respectively. Injection of Cu-DMG into Galleria mellonella before C. jejuni inoculation significantly increased the insect survival rate compared to the control group. In chickens, oral administration of DMG or Cu-DMG decreased and even abolished C. jejuni colonization in some cases, compared to both water-only and Cu-only control groups. The latter finding is important, since campylobacteriosis is the leading bacterial foodborne infection, and chicken meat constitutes the major foodborne source.

Clostridium butyricum relieve the visceral hypersensitivity in mice induced by Citrobacter rodentium infection with chronic stress

Background

Visceral hypersensitivity is a common symptom in patients with post-infectious irritable bowel syndrome (PI-IBS), and change of the microbiota is a vital etiological factor of it. Clostridium butyricum (C. butyricum) is one of the probiotics which is reported as the active components in the treatment of IBS, especially IBS with diarrhea. Citrobacter rodentium (C. rodentium) is an enteropathogenic bacteria which can produce self-limiting colitis in mice, which have been used to produce a PI-IBS-like mice model. Whether C. butyricum could influence the visceral hypersensitivity and gut microbiota of PI-IBS is still unknown. Our study aimed to examine whether the intervention of C. butyricum or antibiotics could affect the etiology of visceral hypersensitivity.

Methods

C57BL/6 male mice were gavaged with the C. rodentium to induce a infective colitis. The C. butyricum and antibiotic compound were used to intervene the infected mice 3 days later. A 9-day chronic water avoidance stress (WAS) process was implemented to help induce the visceral hypersensitivity. The abdominal withdrawal reflex (AWR) score was assayed to indicate the visceral hypersensitivity of different groups. On the 7th, 14th, and 30th days after infection, mice feces were collected and high-throughput sequencing was carried out to analyze their gut microbiota.

Results

Combined, the C. rodentium infection plus chronic stress (WAS) could induce the visceral hypersensitivity in mice. Treatment of the C. butyricum after C. rodentium infection could relieve visceral hypersensitivity of mice, while no difference was observed in the antibiotic treatment group. The gut microbiota diversity of C. rodentium infected mice was similar to the uninfected mice, while there were different microbial communities structure between them. The Shannon and Chao indexes significantly decreased in the antibiotic treatment group compared to other groups at 7th, 14th, and 30th days post-infection, while treatment of C. butyricum could maintain the indexes within normal range. At day 14 after infection, the structure of microbiota headed towards normality after the C. butyricum treatment. After the WAS, the Shannon and Chao indexes of the control group decreased and the structure of microbiota changed. The C. butyricum treatment could prevent these changes of the gut microbiota induced by WAS.

Conclusion

C. butyricum could relieve the visceral hypersensitivity in mice induced by C. rodentium infection plus chronic stress. It could also remodel the microbiota change caused by the infection and chronic stress. It may be a more effective treatment strategy for PI-IBS than antibiotics.

Central regulatory mechanisms of visceral sensation in response to colonic distension with special reference to brain orexin

Visceral hypersensitivity is a major pathophysiology in irritable bowel syndrome (IBS). Although brain-gut interaction is considered to be involved in the regulation of visceral sensation, little had been known how brain controls visceral sensation. To improve therapeutic strategy in IBS, we should develop a novel approach to control visceral hypersensitivity. Here, we summarized recent data on central control of visceral sensation by neuropeptides in rats. Orexin, ghrelin or oxytocin in the brain is capable of inducing visceral antinociception. Dopamine, cannabinoid, adenosine, serotonin or opioid in the central nervous system (CNS) plays a role in the visceral hyposensitivity. Central ghrelin, levodopa or morphine could induce visceral antinociception via the orexinergic signaling. Orexin induces visceral antinociception through dopamine, cannabinoid, adenosine or oxytocin. Orexin nerve fibers are identified widely throughout the CNS and orexins are implicated in a number of functions. With regard to gastrointestinal functions, in addition to its visceral antinociception, orexin acts centrally to stimulate gastrointestinal motility and improve intestinal barrier function. Brain orexin is also involved in regulation of sleep/awake cycle and anti-depressive action. From these evidence, we would like to make a hypothesis that decreased orexin signaling in the brain may play a role in the pathophysiology in a part of patients with IBS who are frequently accompanied with sleep disturbance, depressive state and disturbed gut functions such as gut motility disturbance, leaky gut and visceral hypersensitivity.

Mast Cell Regulation and Irritable Bowel Syndrome: Effects of Food Components with Potential Nutraceutical Use

Mast cells are key actors in inflammatory reactions. Upon activation, they release histamine, heparin and nerve growth factor, among many other mediators that modulate immune response and neuron sensitization. One important feature of mast cells is that their population is usually increased in animal models and biopsies from patients with irritable bowel syndrome (IBS). Therefore, mast cells and mast cell mediators are regarded as key components in IBS pathophysiology. IBS is a common functional gastrointestinal disorder affecting the quality of life of up to 20% of the population worldwide. It is characterized by abdominal pain and altered bowel habits, with heterogeneous phenotypes ranging from constipation to diarrhea, with a mixed subtype and even an unclassified form. Nutrient intake is one of the triggering factors of IBS. In this respect, certain components of the daily food, such as fatty acids, amino acids or plant-derived substances like flavonoids, have been described to modulate mast cells' activity. In this review, we will focus on the effect of these molecules, either stimulatory or inhibitory, on mast cell degranulation, looking for a nutraceutical capable of decreasing IBS symptoms.

Effects of probiotic supplementation on post-infectious irritable bowel syndrome in rodent model

BACKGROUND

Probiotics have been reported to be the active component used in the treatment of many functional gastrointestinal symptoms and syndromes. Lactobacillus and yeast culture are extensively used in probiotic supplements and traditional treatments for irritable bowel syndrome (IBS). The aim of this study was to investigate the effects of probiotic treatments (Lactobacillus acidophilus LA5, Bifidobacterium animalis subsp. lactis BB12 and Saccharomyces cerevisiae var. boulardii) on the behavioral response, targeted gene expression and pro-inflammatory cytokine levels of Pi (Post infectious)-IBS -induced mice.

METHODS

Pathogen-free male C57L/B6 mice and the Trichinella-infected mice were used to measure the score of abdominal withdrawal reflex (AWR). To compare molecular, biological and biochemical evidences of given probiotics with normal and positive control groups in mice, we conducted quantitative reverse transcription polymerase chain reaction (RT-qPCR), western blotting, and cytokine analysis.

RESULTS

Pi-IBS-induced immune response was confirmed that PAR-2 mRNA level was significantly increased by Trichinella infection (P < 0.05). The reduction of Pi-IBS symptoms through Trichinella infection and the effects of given probiotics were confirmed by a change in the protein levels of cytokines (P < 0.05). In addition, the administration of DW (Daewon) probiotics significantly decreased serum levels of IL-1 and IL-6 (P < 0.05).

CONCLUSIONS

We have demonstrated that the given probiotics decreased pro-inflammatory cytokine levels in both the control and Pi-IBS induced mice. Taken all the results together, the results support that DW probiotics has a potential as a probiotic medication for patient with IBS via regulating TNF-α and IL-6 protein levels and serum IL-1 and IL-6 levels.

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.

Giardia duodenalis induces pathogenic dysbiosis of human intestinal microbiota biofilms

Giardia duodenalis is a prevalent cause of acute diarrheal disease worldwide. However, recent outbreaks in Italy and Norway have revealed a link between giardiasis and the subsequent development of chronic post-infectious irritable bowel syndrome. While the mechanisms underlying the causation of post-infectious irritable bowel syndrome remain obscure, recent findings suggest that alterations in gut microbiota communities are linked to the pathophysiology of irritable bowel syndrome. In the present study, we use a laboratory biofilm system to culture and enrich mucosal microbiota from human intestinal biopsies. Subsequently, we show that co-culture with Giardia induces disturbances in biofilm species composition and biofilm structure resulting in microbiota communities that are intrinsically dysbiotic - even after the clearance of Giardia. These microbiota abnormalities were mediated in part by secretory-excretory Giardia cysteine proteases. Using in vitro cell culture and germ-free murine infection models, we show that Giardia-induced disruptions of microbiota promote bacterial invasion, resulting in epithelial apoptosis, tight junctional disruption, and bacterial translocation across an intestinal epithelial barrier. Additionally, these dysbiotic microbiota communities resulted in increased activation of the Toll-like receptor 4 signalling pathway, and overproduction of the pro-inflammatory cytokine IL-1beta in humanized germ-free mice. Previous studies that have sought explanations and risk factors for the development of post-infectious irritable bowel syndrome have focused on features of enteropathogens and attributes of the infected host. We propose that polymicrobial interactions involving Giardia and gut microbiota may cause persistent dysbiosis, offering a new interpretation of the reasons why those afflicted with giardiasis are predisposed to gastrointestinal disorders post-infection.

Pathogenesis, Experimental Models and Contemporary Pharmacotherapy of Irritable Bowel Syndrome: Story About the Brain-Gut Axis

Background

Although the precise pathophysiology of irritable bowel syndrome (IBS) remains unknown, it is generally considered to be a disorder of the brain-gut axis, representing the disruption of communication between the brain and the digestive system. The present review describes advances in understanding the pathophysiology and experimental approaches in studying IBS, as well as providing an update of the therapies targeting brain-gut axis in the treatment of the disease.

Methods

Causal factors of IBS are reviewed. Following this, the preclinical experimental models of IBS will be introduced. Besides, both current and future therapeutic approaches of IBS will be discussed.

Results

When signal of the brain-gut axis becomes misinterpreted, it may lead to dysregulation of both central and enteric nervous systems, altered intestinal motility, increased visceral sensitivity and consequently contributing to the development of IBS. Interference of the brain-gut axis can be modulated by various psychological and environmental factors. Although there is no existing animal experiment that can represent this complex multifactorial disease, these in vivo models are clinically relevant readouts of gastrointestinal functions being essential to the identification of effective treatments of IBS symptoms as well as their molecular targets. Understanding the brain-gut axis is essential in developing the effective therapy for IBS. Therapies include improvement of GI motor functions, relief of visceral hypersensitivity and pain, attenuation of autonomic dysfunctions and suppression of mucosal immune activation.

Conclusion

Target-oriented therapies that provide symptomatic, psychological and physiological benefits could surely help to improve the quality of life of IBS patients.

Irritable bowel syndrome and inflammatory bowel disease overlap syndrome: pieces of the puzzle are falling into place

Irritable bowel syndrome (IBS), a common gastrointestinal disorder involving the gut-brain axis, and inflammatory bowel disease (IBD), a chronic relapsing inflammatory disorder, are both increasing in incidence and prevalence in Asia. Both have significant overlap in terms of symptoms, pathophysiology, and treatment, suggesting the possibility of IBS and IBD being a single disease entity albeit at opposite ends of the spectrum. We examined the similarities and differences in IBS and IBD, and offer new thoughts and approaches to the disease paradigm.

Recent advances in the diagnosis of irritable bowel syndrome

The symptom-based diagnosis of irritable bowel syndrome (IBS) has not been established in everyday clinical practice, and the diagnosis of this disorder remains one of exclusion. It has been demonstrated that the densities of duodenal chromogranin A, rectal peptide YY and somatostatin cells are good biomarkers for the diagnosis of sporadic IBS, and low-grade mucosal inflammation is a promising biomarker for the diagnosis of postinfectious IBS. Genetic markers are not useful as biomarkers for IBS since the potential risk genes have yet to be validated, and the intestinal microbiota cannot be used because of the lack of an association between a specific bacterial species and IBS. Furthermore, gastrointestinal dysmotility and visceral hypersensitivity tests produce results that are too nonconsistent and noncharacteristic to be used in the diagnosis of IBS. A combination of symptom-based assessment, exclusion of overlapping gastrointestinal diseases and positive biomarkers appears to be the best way to diagnose IBS.

Interventions for post-infectious irritable bowel syndrome: a systematic review of treatment efficacy

Background

Post-infectious irritable bowel syndrome (PI-IBS) due to traveler’s diarrhea is the second most common illness seen in post-travel clinics, yet its optimal management remains unknown. We performed a systematic review to evaluate treatment efficacy in PI-IBS.

Methods

We searched Medline, EMBASE, LILACS, CINAHL, CAB abstracts, and the Cochrane Library to February 3, 2014 for intervention studies of the pharmacologic and non-pharmacologic management of PI-IBS and examined the evidence according to a modified Grading of Recommendations Assessment, Development, and Evaluation (GRADE) scale.

Results

Of 336 records, 9 studies were included. Eight studies of pharmacologic interventions examined 5 agents (mesalazine or mesalamine, ondansetron, prednisolone, cholestyramine, and metronidazole). One study examined the non-pharmacologic intervention of different infant nutritional formulas following acute gastroenteritis. The quality of the evidence to date was low, with small sample size (fewer than 50 participants) and short duration of follow-up. Overall, the efficacy of pharmacological treatment ranged from no benefit (ondansetron and prednisolone) to moderately beneficial (cholestyramine and metronidazole). The evidence for mesalazine was equivocal: one study showed benefit, two others showed none.

Conclusions

Heterogeneity in outcome measures and low strength of evidence preclude recommendations on the optimal management of PI-IBS by a specific agent. More comparative intervention research into PI-IBS treatment is needed for consistent best practice in PI-IBS management. Clinicians may elect to pursue therapeutic trials of mesalazine, cholestyramine, or metronidazole in individual patients, but should be aware that data supporting the efficacy of these agents is limited.

Electronic supplementary material

The online version of this article (doi:10.1186/s40794-015-0002-9) contains supplementary material, which is available to authorized users.

Inflammatory cytokines promote growth of intestinal smooth muscle cells by induced expression of PDGF-Rβ

Thickening of the inflamed intestinal wall involves growth of smooth muscle cells (SMC), which contributes to stricture formation. Earlier, the growth factor platelet-derived growth factor (PDGF)-BB was identified as a key mitogen for SMC from the rat colon (CSMC), and CSMC growth in colitis was associated with both appearance of its receptor, PDGF-Rβ and modulation of phenotype. Here, we examined the role of inflammatory cytokines in inducing and modulating the growth response to PDGF-BB. CSMC were enzymatically isolated from Sprague–Dawley rats, and the effect of tumour necrosis factor (TNF)-α, interleukin (IL)-1β, transforming growth factor (TGF), IL-17A and IL-2 on CSMC growth and responsiveness to PDGF-BB were assessed using proliferation assays, PCR and western blotting. Conditioned medium (CM) was obtained at 48 hrs of trinitrobenzene sulphonic acid-induced colitis. Neither CM alone nor cytokines caused proliferation of early-passage CSMC. However, CM from inflamed, but not control colon significantly promoted the effect of PDGF-BB. IL-1β, TNF-α and IL-17A, but not other cytokines, increased the effect of PDGF-BB because of up-regulation of mRNA and protein for PDGF-Rβ without change in receptor phosphorylation. PDGF-BB was identified in adult rat serum (RS) and RS-induced CSMC proliferation was inhibited by imatinib, suggesting that blood-derived PDGF-BB is a local mitogen in vivo. In freshly isolated CSMC, CM from the inflamed colon as well as IL-1β and TNF-α induced the early expression of PDGF-Rβ, while imatinib blocked subsequent RS-induced cell proliferation. Thus, pro-inflammatory cytokines both initiate and maintain a growth response in CSMC via PDGF-Rβ and serum-derived PDGF-BB, and control of PDGF-Rβ expression may be beneficial in chronic intestinal inflammation.

Increased risk for irritable bowel syndrome after acute diverticulitis

BACKGROUND & AIMS

Individuals with diverticulosis frequently also have irritable bowel syndrome (IBS), but there are no longitudinal data to associate acute diverticulitis with subsequent IBS, functional bowel disorders, or related emotional distress. In patients with postinfectious IBS, gastrointestinal disorders cause long-term symptoms, so we investigated whether diverticulitis might lead to IBS. We compared the incidence of IBS and functional bowel and related affective disorders among patients with diverticulitis.

METHODS

We performed a retrospective study of patients followed up for an average of 6.3 years at a Veteran's Administration medical center. Patients with diverticulitis were identified based on International Classification of Diseases, 9th revision codes, selected for the analysis based on chart review (cases, n = 1102), and matched with patients without diverticulosis (controls, n = 1102). We excluded patients with prior IBS, functional bowel, or mood disorders. We then identified patients who were diagnosed with IBS or functional bowel disorders after the diverticulitis attack, and controls who developed these disorders during the study period. We also collected information on mood disorders, analyzed survival times, and calculated adjusted hazard ratios.

RESULTS

Cases were 4.7-fold more likely to be diagnosed later with IBS (95% confidence interval [CI], 1.6-14.0; P = .006), 2.4-fold more likely to be diagnosed later with a functional bowel disorder (95% CI, 1.6-3.6; P < .001), and 2.2-fold more likely to develop a mood disorder (CI, 1.4-3.5; P < .001) than controls.

CONCLUSIONS

Patients with diverticulitis could be at risk for later development of IBS and functional bowel disorders. We propose calling this disorder postdiverticulitis IBS. Diverticulitis appears to predispose patients to long-term gastrointestinal and emotional symptoms after resolution of inflammation; in this way, postdiverticulitis IBS is similar to postinfectious IBS.

Effect of probiotic bacteria on the intestinal microbiota in irritable bowel syndrome

BACKGROUND AND AIM

In irritable bowel syndrome (IBS), the gut microbiota may be altered. Probiotic bacteria appear to be therapeutically effective. We characterized the mucosa-associated microbiota, and determined the clinical and microbiological effects of orally administered probiotic bacteria, in patients with IBS.

METHODS

Mucosal microbiota from rectal biopsies of IBS patients and controls were assessed on the V1 and V2 variable regions of the 16S ribosomal RNA gene amplified using 454 pyrosequencing. Clinical symptoms and changes in mucosal microbiota were assessed in IBS patients before and after 4 weeks of treatment with probiotic mix VSL#3.

RESULTS

Ten IBS subjects (eight female; mean age 46 years) were included. At week 4 of probiotic therapy, six patients showed symptom improvement on global symptom assessment compared with baseline (P = 0.031). Before therapy, intestinal microbiota of IBS subjects differed significantly from that of healthy controls, with less diversity and evenness than controls (n = 9; P < 0.05), increased abundance of Bacteroidetes (P = 0.014) and Synegitestes (P = 0.017), and reduced abundance of Actinobacteria (P = 0.004). The classes Flavobacteria (P = 0.028) and Epsilonproteobacteria (P = 0.017) were less enriched in IBS. Abundance differences were largely consistent from the phylum to genus level. Probiotic treatment in IBS patients was associated with a significant reduction of the genus Bacteroides (all taxonomy levels; P < 0.05) to levels similar to that of controls.

CONCLUSION

In this pilot study, global and deep molecular analysis demonstrates an altered mucosal microbiota composition in IBS. Probiotic leads to detectable changes in the microbiota. These effects of probiotic bacteria may contribute to their therapeutic benefit.

Streptomycin-induced inflammation enhances Escherichia coli gut colonization through nitrate respiration

Treatment with streptomycin enhances the growth of human commensal Escherichia coli isolates in the mouse intestine, suggesting that the resident microbial community (microbiota) can inhibit the growth of invading microbes, a phenomenon known as “colonization resistance.” However, the precise mechanisms by which streptomycin treatment lowers colonization resistance remain obscure. Here we show that streptomycin treatment rendered mice more susceptible to the development of chemically induced colitis, raising the possibility that the antibiotic might lower colonization resistance by changing mucosal immune responses rather than by preventing microbe-microbe interactions. Investigation of the underlying mechanism revealed a mild inflammatory infiltrate in the cecal mucosa of streptomycin-treated mice, which was accompanied by elevated expression of Nos2, the gene that encodes inducible nitric oxide synthase. In turn, this inflammatory response enhanced the luminal growth of E. coli by nitrate respiration in a Nos2-dependent fashion. These data identify low-level intestinal inflammation as one of the factors responsible for the loss of resistance to E. coli colonization after streptomycin treatment.

Our intestine is host to a complex microbial community that confers benefits by educating the immune system and providing niche protection. Perturbation of intestinal communities by streptomycin treatment lowers “colonization resistance” through unknown mechanisms. Here we show that streptomycin increases the inflammatory tone of the intestinal mucosa, thereby making the bowel more susceptible to dextran sulfate sodium treatment and boosting the Nos2-dependent growth of commensal Escherichia coli by nitrate respiration. These data point to the generation of alternative electron acceptors as a by-product of the inflammatory host response as an important factor responsible for lowering resistance to colonization by facultative anaerobic bacteria such as E. coli.

Effect of repeated Campylobacter jejuni infection on gut flora and mucosal defense in a rat model of post infectious functional and microbial bowel changes

BACKGROUND

Campylobacter jejuni infection is a leading cause of gastroenteritis and post infectious irritable bowel syndrome (PI-IBS). Unanswered questions include the role of cytokines, effects on gut flora, and why IBS is not more prevalent in countries with higher gastroenteritis rates. Therefore, we determined the effects of early and repeat C. jejuni infections on post infectious phenotypes, gut flora, and cytokine levels in a rat model of functional bowel and microbial changes.

METHODS

Sprague-Dawley rats were gavaged with 10(8)  cfu C. jejuni as juveniles and again as adults (J+/A+), as adults only (J-/A+), or vehicle (controls). Stool consistency during acute colonization, post infectious stool wet weight, total bacteria and Methanobrevibacter smithii levels in bowel segments, and ileal cytokines were evaluated.

KEY RESULTS

C. jejuni colonization was longer for first exposures as juveniles (43.4 ± 1.7 days) vs. adults (30.4 ± 3.5 days) (P < 0.01) and shortest for second exposures (10.5 ± 1.7 days, P < 0.05). Small intestinal bacterial overgrowth (SIBO) was more prevalent in J+/A+ (47%) than J-/A+ rats (26%) (P = 0.019), but J-/A+ rats had greater stool consistency alterations (P < 0.01). Ileal β-defensin 2, TLR-4, IL-8, and β-defensin 6 levels were increased in J-/A+ rats and further increased in J+/A+ rats; TNF-α was highest and IL6 lowest in J-/A+ rats. Total bacteria increased, and M. smithii decreased, with successive infections.

CONCLUSIONS & INFERENCES

We conclude that C. jejuni infection results in long-term alterations in small bowel flora, including methanogens. Mucosal defense mediators appear related to the number of infections, but not to SIBO development or the development of functional bowel phenotypes.

Low prevalence of 'classical' microscopic colitis but evidence of microscopic inflammation in Asian irritable bowel syndrome patients with diarrhoea

Background

There is increasing evidence for the role of microscopic inflammation in patients with IBS. We aimed to examine the prevalence of microscopic colitis and inflammation in Malaysian IBS patients with diarrhoea (IBS-D).

Methods

Consecutive patients who met the Rome III criteria for IBS-D and asymptomatic controls were prospectively recruited. Colonoscopy was performed in all study subjects and systematic biopsies taken from all segments of the colon. The diagnosis of lymphocytic colitis and collagenous colitis was made using previously defined criteria. Patients with post infectious IBS were excluded.

Results

120 subjects (74 IBS-D, 46 controls) were recruited during the study period. In the IBS-D group, the colonoscopic (macroscopic) findings were as follows; normal findings n = 58 (78.4%), diverticula disease n = 5 (6.8%), diminutive polyps n = 9 (12.2%) and haemorrhoids n = 2(2.7%). No subject under the age of 40 had any significant findings. Microscopically, there was only one case (1.3%) with histology consistent with collagenous colitis. However, the IBS-D patients had a higher prevalence of moderate microscopic inflammation (n = 11, 14.9%) compared to controls (n = 1, 2.2%) (p = 0.005).

Conclusions

‘Classical’ microscopic colitis is uncommon in Malaysian patients with IBS-D but a significant number of adults showed evidence of microscopic inflammation.

Correlation between anxiety-depression status and cytokines in diarrhea-predominant irritable bowel syndrome

The aim of this study was to investigate the correlation between anxiety-depression status and cytokines in diarrhea-predominant irritable bowel syndrome (IBS-D). IBS-D patients were divided into an anxiety-depression IBS-D group and a non-anxiety-depression IBS-D group. Patients without IBS, anxiety or depression were selected as the control group. Scoring was performed using the self-rating anxiety scale (SAS) and self-rating depression scale (SDS). Levels of IL-1β and IL-10 in the blood and sigmoid colon mucosa were detected, and the proportions of IL-1β- and IL-10-positive cells in the sigmoid colon mucosa were determined. The results demonstrated that the SDS and SAS scores in the IBS-D group were significantly higher than those in the control group (P<0.05). The levels of IL-1β in the blood and sigmoid colon mucosa and the proportion of IL-1β-positive cells in the sigmoid colon mucosa in the IBS-D group were significantly higher than those in the control group (P<0.05). The levels of IL-10 in the blood and sigmoid colon mucosa and the proportion of IL-10-positive cells in the IBS-D group were significantly lower than those in the control group (P<0.05). The levels of IL-1β in the blood and sigmoid colon mucosa and the proportion of IL-1β-positive cells in the anxiety-depression IBS-D group were significantly higher than those in the non-anxiety-depression IBS-D group, and the levels of IL-10 and the proportion of IL-10-positive cells in the anxiety-depression IBS-D group were significantly lower than those in the non-anxiety-depression IBS-D group (P<0.05). Anxiety-depression status may cause the IL-1β and IL-10 levels in IBS patients to change and result in an imbalance of the proinflammatory and anti-inflammatory cytokines, leading to the occurrence or aggravation of IBS.

A randomised clinical trial (RCT) of a symbiotic mixture in patients with irritable bowel syndrome (IBS): effects on symptoms, colonic transit and quality of life

PURPOSE

The aim of this study is to test in a double-blinded, randomised placebo-controlled study the effects of a commercially available multi-strain symbiotic mixture on symptoms, colonic transit and quality of life in irritable bowel syndrome (IBS) patients who meet Rome III criteria.

BACKGROUND

There is only one other double-blinded RCT on a single-strain symbiotic mixture in IBS.

METHODS

This is a double-blinded, randomised placebo-controlled study of a symbiotic mixture (Probinul, 5 g bid) over 4 weeks after 2 weeks of run-in. The primary endpoints were global satisfactory relief of abdominal flatulence and bloating. Responders were patients who reported at least 50 % of the weeks of treatment with global satisfactory relief. The secondary endpoints were change in abdominal bloating, flatulence, pain and urgency by a 100-mm visual analog scale, stool frequency and bowel functions on validated adjectival scales (Bristol Scale and sense of incomplete evacuation). Pre- and post-treatment colonic transit time (Metcalf) and quality of life (SF-36) were assessed.

RESULTS

Sixty-four IBS patients (symbiotic n = 32, 64 % females, mean age 38.7 ± 12.6 years) were studied. This symbiotic mixture reduced flatulence over a 4-week period of treatment (repeated-measures analysis of covariance, p < 0.05). Proportions of responders were not significantly different between groups. At the end of the treatment, a longer rectosigmoid transit time and a significant improvement in most SF-36 scores were observed in the symbiotic group.

CONCLUSIONS

This symbiotic mixture has shown a beneficial effect in decreasing the severity of flatulence in IBS patients, a lack of adverse events and a good side-effect profile; however, it failed to achieve an improvement in global satisfactory relief of abdominal flatulence and bloating. Further studies are warranted.

Clustering and stability of functional lower gastrointestinal symptom after enteric infection

BACKGROUND

Current diagnostic criteria for functional gut disorder are based on symptom clusters observed after sporadic onset. It remains unclear whether symptoms group similarly in functional disorders of postinfectious etiology. We utilized observational data from the Walkerton Health Study (WHS) to: (i) determine groupings of functional gastrointestinal symptoms among patients exposed to acute gastroenteritis (GE), and (ii) assess the stability of these symptoms grouping over time.

METHODS

WHS participants 16 years of age and older at the time of the outbreak were included, if they had completed a modified Talley's Bowel Disease Questionnaire (BDQ) and responded 'yes' to a screening question as to whether they had experienced abdominal pain in the last 2 weeks. Exploratory factor analysis (EFA) using tetrachoric correlations was undertaken to identify symptom constructs. Hierarchical cluster analysis using the k-means method was used to create cluster groupings of patients based on these factors. Confirmatory factors analysis using responses to BDQ questionnaire administered at 4, 6, and 8 years after the outbreak was performed to assess stability of symptom domains over time.

KEY RESULTS

A total of 773 participants were eligible for inclusion [62.2% female, mean age 43.1 years (SD = 16.9)]. Eighty-four percent were exposed to acute GE during the outbreak. Two symptom groupings of abdominal pain with either diarrhea or constipation together explained 85.7% of the total variance. Cluster analysis identified four patients groupings based on these factors. These clusters could be qualitatively described as diarrhea- and constipation-predominant, mixed bowel pattern, and no predominance of bowel movements abnormalities. Results of the confirmatory factor analysis validating symptom domains identified in Year 1 showed that the baseline model was acceptable at 4 and 6 years after the outbreak and approached acceptability at 8 years. Values of root mean square error of approximation were 0.071 (90% CI: 0.053, 0.089) at 4 and 0.071 (90% CI: 0.049, 0.092) at 6 years and 0.089 (90% CI: 0.065, 0.114) at 8 years.

CONCLUSIONS & INFERENCES

The majority of subjects with postinfectious functional bowel disorders belong to groups with symptoms of abdominal pain and either diarrhea or constipation. These symptom groupings were stable across time.

A global perspective on irritable bowel syndrome: a consensus statement of the World Gastroenterology Organisation Summit Task Force on irritable bowel syndrome

Irritable bowel syndrome (IBS) is common in western Europe and North America, and many aspects of its epidemiology, risk factors, and natural history have been described in these regions. Recent data suggest, however, that IBS is also common in the rest of the world and there has been some evidence to suggest some differences in demographics and presenting features between IBS in the west and as it is experienced elsewhere. The World Gastroenterology Organization, therefore, established a Task Force comprising experts on the topic from all parts of the world to examine IBS from a global perspective. IBS does, indeed, seem to be common worldwide though with some significant variations in prevalence rates between regions and countries and there may well be some potentially interesting variations in presenting symptoms and sex distribution. The global map of IBS is far from complete; community-based prevalence data is not available from many areas. Furthermore, while some general trends are evident in terms of IBS impact and demographics, international comparisons are hampered by differences in diagnostic criteria, study location and methodology; several important unanswered questions have been identified that should form the basis for future collaborative research and have the potential to shed light on this challenging disorder.

Effects of octreotide on jejunal hypersensitivity triggered by Cryptosporidium parvum intestinal infection in an immunocompetent suckling rat model

BACKGROUND

Similar to other bacterial or protozoan infections, human cryptosporidiosis may trigger postinfectious irritable bowel syndrome (IBS)-like symptoms, a condition in which enhanced visceral perception of pain during intestinal distension plays a pivotal role. In an immunocompetent suckling rat model which mimicks features of postinfectious IBS, Cryptosporidium parvum infection induces long-lasting jejunal hypersensitivity to distension in association with intestinal activated mast cell accumulation. The aim of the present study was to explore in this model whether octreotide, a somatostatin agonist analog, could prevent the development of jejunal hypersensitivity and intestinal mast cell/nerve fiber accumulation.

METHODS

Five-day-old Sprague-Dawley rats were infected with C. parvum and treated 10 days later with octreotide (50 g kg(-1) day(-1), i.p.) for 7 days.

KEY RESULTS

Compared with untreated infected rats, octreotide treatment of infected rats resulted in increased weight gain [day 23 postinfection (PI)], decreased food intake (day 16 PI), and a reduction in jejunal villus alterations (day 14 PI), CD3(+) IEL (day 37 PI) and mast cell (days 37 and 50 PI) accumulations, nerve fiber densities (day 50 PI), and hypersensitivity to distension (day 120 PI). In uninfected rats, the effects of octreotide treatment were limited to higher weight gain (days 16 and 23 PI) and decreased food intake (day 23 PI) compared with uninfected-untreated rats.

CONCLUSIONS & INFERENCES

Data confirms the relevance of the present rat model to postinfectious IBS studies and prompt further investigation of somatostatin-dependent regulatory interactions in cryptosporidiosis.

Treatment of postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome with mesalazine

CONTEXT

Recent studies support the hypothesis that postinfectious irritable bowel syndrome and some irritable bowel syndrome patients display persistent signs of minor mucosal inflammation. Mesalazine has intestinal anti-inflammatory properties including cyclooxygenase and prostaglandin inhibition. The effects of mesalazine on postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome patients are still unknown.

OBJECTIVE

To observe the effects of mesalazine on postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome with diarrhea patients.

METHODS

Based on Rome III criteria, 61 irritable bowel syndrome with diarrhea patients (18 years old or more) were included in the evaluation. Patients were divided into two groups: postinfectious irritable bowel syndrome group, with 18 patients medicated with mesalazine 800 mg 3 times a day for 30 days; noninfective irritable bowel syndrome group, with 43 patients medicated with mesalazine 800 mg 3 times a day for 30 days. Symptom evaluations at baseline and after treatment were performed by means of a four-point Likert scale including stool frequency, stool form and consistency (Bristol Stool Scale), abdominal pain and distension (maximum score: 16; minimum score: 4).

RESULTS

Postinfectious irritable bowel syndrome group presented a statistically significant reduction of the total symptom score (P<0.0001). The stool frequency was significantly reduced (P<0.0001), and stool consistency, improved (P<0.0001). Abdominal pain (P<0.0001) and abdominal distension were significantly reduced (P<0.0001). Noninfective irritable bowel syndrome group presented a statistically significant reduction of total symptom score (P<0.0001). Also, the stool frequency was significantly reduced (P<0.0001) and stool consistency, improved (P<0.0001). Abdominal pain (P<0.0001) and abdominal distention were significantly reduced (P<0.0001). There was no statistical difference between postinfectious irritable bowel syndrome group and noninfective irritable bowel syndrome group on total symptom score results at 30th day of therapy with mesalazine 800 mg 3 times a day. (P = 0.13).

CONCLUSION

Mesalazine reduced key symptoms of postinfectious irritable bowel syndrome and noninfective irritable bowel syndrome with diarrhea patients.

Irritable bowel syndrome, gut microbiota and probiotics

Irritable bowel syndrome (IBS) is a complex disorder characterized by abdominal symptoms including chronic abdominal pain or discomfort and altered bowel habits. The etiology of IBS is multifactorial, as abnormal gut motility, visceral hypersensitivity, disturbed neural function of the brain-gut axis and an abnormal autonomic nervous system are all implicated in disease progression. Based on recent experimental and clinical studies, it has been suggested that additional etiological factors including low-grade inflammation, altered gut microbiota and alteration in the gut immune system play important roles in the pathogenesis of IBS. Therefore, therapeutic restoration of altered intestinal microbiota may be an ideal treatment for IBS. Probiotics are live organisms that are believed to cause no harm and result in health benefits for the host. Clinical efficacy of probiotics has been shown in the treatment or prevention of some gastrointestinal inflammation-associated disorders including traveler's diarrhea, antibiotics-associated diarrhea, pouchitis of the restorative ileal pouch and necrotizing enterocolitis. The molecular mechanisms, as cause of IBS pathogenesis, affected by altered gut microbiota and gut inflammation-immunity are reviewed. The effect of probiotics on the gut inflammation-immune systems and the results from clinical trials of probiotics for the treatment of IBS are also summarized.

Questioning the bacterial overgrowth hypothesis of irritable bowel syndrome: an epidemiologic and evolutionary perspective

Although studies indicate that small intestinal bacterial overgrowth (SIBO) is prevalent in irritable bowel syndrome (IBS), it remains unclear whether SIBO causes IBS. This review presents an epidemiologic and evolutionary inquiry that questions the bacterial overgrowth hypothesis of IBS, as follows. (1) Although the hypothesis may be biologically plausible, there is also a strong rationale for competing hypotheses; it is unlikely that SIBO is the predominant cause of IBS in all comers, because competing explanations are sensible and defensible. Moreover, data indicate that the test used to promulgate the SIBO hypothesis - the lactulose hydrogen breath test - may not have measured SIBO in the first place. (2) We do not have evidence of SIBO being absent before IBS symptoms, and present after IBS emerges. (3) There is not a dose-response relationship between small intestinal microbiota and IBS symptoms. (4) The relationship between SIBO and IBS is highly inconsistent among studies. (5) Many effective IBS therapies do not address SIBO at all, yet have a more favorable "number needed to treat" than antibiotics. (6) IBS does not behave like a traditional infectious disease, suggesting that microbes may not principally cause the syndrome. (7) Other factors may confound the relationship between SIBO and IBS, including proton pump inhibitors. (8) Whereas the brain-gut hypothesis is evolutionary sensible, the bacterial hypothesis is harder to defend from an evolutionary perspective. The article concludes that bacteria may contribute to some IBS symptoms, but that bacteria cannot be the only explanation, and a causal link between SIBO and IBS is not secure.

The microbiome-gut-brain axis: from bowel to behavior

The ability of gut microbiota to communicate with the brain and thus modulate behavior is emerging as an exciting concept in health and disease. The enteric microbiota interacts with the host to form essential relationships that govern homeostasis. Despite the unique enteric bacterial fingerprint of each individual, there appears to be a certain balance that confers health benefits. It is, therefore, reasonable to note that a decrease in the desirable gastrointestinal bacteria will lead to deterioration in gastrointestinal, neuroendocrine or immune relationships and ultimately disease. Therefore, studies focusing on the impact of enteric microbiota on the host and in particular on the central nervous system are essential to our understanding of the influence of this system. Recent studies published in this Journal demonstrate that germ-free mice display alterations in stress-responsivity, central neurochemistry and behavior indicative of a reduction in anxiety in comparison to conventional mice. Such data offer the enticing proposition that specific modulation of the enteric microbiota may be a useful strategy for stress-related disorders and for modulating the co-morbid aspects of gastrointestinal disorders such as irritable bowel syndrome and inflammatory bowel disease.

Post-infectious gastrointestinal symptoms after acute Giardiasis. A 1-year follow-up in general practice

BACKGROUND

Giardia lamblia is endemic in many tropical and subtropical areas of the world, and in Europe and North America a common cause of waterborne outbreaks of gastroenteritis. In 2004, approximately 5000 people were sick with giardiasis during an outbreak in Bergen, Norway.

OBJECTIVE

To investigate the presence of gastrointestinal complaints and persistent infection in a 1-year period after acute giardiasis.

METHODS

From a population (N = 7100) assigned to two general practice clinics, a cohort of 134 patients with clinically defined giardiasis was identified. Of these, 118 gave consent to take part in this study. The patients were asked to submit stool samples 6 months after the acute infection and to return questionnaires delivered by mail 6 and 12 months after the outbreak. Main outcome measures were proportion of patients with persistent infection and/or gastrointestinal symptoms.

RESULTS

Stool samples were submitted by 69.5% (82/118) of the patients after 6 months, and three were positive for G. lamblia. After 6 months, 37.3% (44/118) of the patients reported gastrointestinal symptoms related to their Giardia infection. This proportion went down to 19.2% (19/99) after 12 months. The reported water intake prior to the outbreak was significantly higher in patients with persistent symptoms, but there was no association with gender and neuroticism as has been shown in other studies of functional gastrointestinal disorders.

CONCLUSION

Persistent gastrointestinal symptoms are a common complication after giardiasis in a population most likely previously unexposed to G. lamblia. The results show the need for further investigation of the mechanism involved.

Irritable bowel syndrome: epidemiology, diagnosis and treatment: an update for health-care practitioners

Irritable bowel syndrome (IBS), a chronic gastrointestinal disorder, affects from 3-20% of the US population, depending on sociocultural and comorbid factors. IBS is characterized by a symptom complex of abdominal pain and abnormal bowel habits that present as diarrhea or constipation, and general physical weakness in the absence of abnormal morphological, histological or inflammatory markers. The main diagnostic Rome III criteria as established by international professional organizations are based on exclusion criteria and the occurrence and rate of symptoms. Because the pathophysiology and causes of IBS are poorly understood, treatment approaches are mainly focused on symptom management to maintain everyday functioning and improve quality of life for persons with IBS. The mainstay of intervention is pharmacological treatment with antispasmodics and antidiarrheals for diarrhea, prokinetics and high-fiber diets for constipation, and supportive therapy with low-dose antidepressants to normalize gastrointestinal motility. Other interventions include lifestyle and dietary changes, psychotherapy, herbal therapies and acupuncture. The purpose of this review is to critically assess benefits and risks of current treatment approaches as well as promising complementary and alternative therapies.

Predictors of persistent gastrointestinal symptoms among new presenters to primary care

BACKGROUND AND AIMS

To quantify the relative contribution of environmental, clinical, infection and psychosocial factors in the persistence of gastrointestinal (GI) symptoms among new patients presenting to primary care.

METHODS

We conducted a population-based prospective cohort study of 4986 adults aged 25-65 years. The study team obtained permission from the participants to monitor their general practice records for consultation with GI symptoms and to contact them at that time. Group 1 (n = 177) patients completed a postal questionnaire, whereas those in group 2 (n = 191) completed an identical questionnaire and provided a blood and stool sample. The participants were followed up for 1 and 6 months postconsultation.

RESULTS

Of 610 (12.2%) participants who consulted, 368 (60.3%) agreed to participate. Two hundred and eighty participants (76.1%) completed 1 and 6-month follow-up questionnaires and 106 (37.9%) had persistent (present 1 and 6 months postconsultation) GI symptoms. After adjusting for age, sex, area of residence and duration of symptoms before consultation, symptom persistence was independently predicted by high levels of psychological distress [odds ratio (OR): 2.5, 95% confidence interval (CI): (1.1-5.3)], symptom episode duration of more than 2 h [OR: 3.1, 95% CI: (1.3-7.1)] and symptom interference with daily activities [OR: 2.3, 95% CI: (1.1-4.8)]. Changing diet [OR: 0.2, 95% CI: (0.1-0.9)] and recent gastroenteritis or food poisoning [OR: 0.2, 95% CI: (0.1-0.98)] were associated with protective effects. Infection was not associated. Exposure to three or more of these factors identified 87.3% (n = 92) of the participants with persistent symptoms.

CONCLUSION

The factors measured at the time of consultation with GI symptoms can accurately predict those patients at increased risk of persistent symptoms up to 6 months later.

Serum correlates of the placebo effect in irritable bowel syndrome

BACKGROUND In diseases defined primarily by the subjective nature of patient self-report, placebo effects can overwhelm the capacity of randomized controlled trials to detect medication-placebo differences. Moreover, it is unclear whether such placebo effects represent genuine psychobiological phenomena or just shifts in selective attention. Knowledge of predictors of the placebo response could improve the design of clinical trials and the delivery of personalized medical care. METHODS In patients with irritable bowel syndrome (IBS), a subset of our previous study that were randomized to placebo treatment (sham acupuncture) or no-treatment group (waitlist), we tested an enriched panel of 10 serum biomarkers at the enrolment and the 3rd week of intervention, using a multiplex electrochemiluminescent immunoassay. KEY RESULTS More pronounced changes overtime in serum levels of osteoprotegerin (OPG) have been found in patients who received placebo treatment compared with the waitlist group (P = 0.039). Moreover, serum levels of OPG at baseline were found to be higher (P = 0.0167) in patients who subsequently achieved adequate relief (AR) of their IBS symptoms, independently of their treatment group. Besides, serum levels of TNF-related weak inducer of apoptosis (TWEAK) at baseline were also higher (P = 0.0144) in patients who reported AR and in particular in those who received the placebo treatment. CONCLUSIONS & INFERENCES These two measurable biological parameters associated with placebo, namely serum OPG and TWEAK, provide a proof of principle for discovering putative molecular signatures of placebo response in IBS and perhaps in other illnesses with patient self-reported outcomes.

Severity of Giardia infection associated with post-infectious fatigue and abdominal symptoms two years after

BACKGROUND

A high rate of post-infectious fatigue and abdominal symptoms two years after a waterborne outbreak of giardiasis in Bergen, Norway in 2004 has previously been reported. The aim of this report was to identify risk factors associated with such manifestations.

METHODS

All laboratory confirmed cases of giardiasis (n = 1262) during the outbreak in Bergen in 2004 received a postal questionnaire two years after. Degree of post-infectious abdominal symptoms and fatigue, as well as previous abdominal problems, was recorded. In the statistical analyses number of treatment courses, treatment refractory infection, delayed education and sick leave were used as indices of protracted and severe Giardia infection. Age, gender, previous abdominal problems and symptoms during infection were also analysed as possible risk factors. Simple and multiple ordinal logistic regression models were used for the analyses.

RESULTS

The response rate was 81% (1017/1262), 64% were women and median age was 31 years (range 3-93), compared to 61% women and 30 years (range 2-93) among all 1262 cases. Factors in multiple regression analysis significantly associated with abdominal symptoms two years after infection were: More than one treatment course, treatment refractory infection, delayed education, bloating and female gender. Abdominal problems prior to Giardia infection were not associated with post-infectious abdominal symptoms. More than one treatment course, delayed education, sick leave more than 2 weeks, and malaise at the time of infection, were significantly associated with fatigue in the multiple regression analysis, as were increasing age and previous abdominal problems.

CONCLUSION

Protracted and severe giardiasis seemed to be a risk factor for post-infectious fatigue and abdominal symptoms two years after clearing the Giardia infection.

Activation of human enteric neurons by supernatants of colonic biopsy specimens from patients with irritable bowel syndrome

BACKGROUND & AIMS

Pathological features in irritable bowel syndrome (IBS) include alterations in mucosal cell content and mediator release that might alter signaling to nearby submucosal neurons.

METHODS

Voltage sensitive dye imaging was used to record the effects of mediators, released from mucosal biopsies of IBS patients, on cell bodies of 1207 submucosal neurons from 76 human colonic tissue specimens. Supernatants, containing these mediators, were collected following incubation with colonic mucosal biopsies from 7 patients with diarrhea-predominant IBS (D-IBS), 4 with constipation-predominant IBS (C-IBS), and 4 healthy controls. Serotonin, histamine and tryptase concentrations in supernatants and lamina propria mast cell density were determined.

RESULTS

In contrast to controls, IBS supernatants significantly increased the rate of spike discharge in 58% of human submucosal neurons. Neurons that responded to IBS supernatant had a median spike frequency of 2.4 Hz compared to 0 Hz for control supernatants. Supernatants from C-IBS and D-IBS evoked similar spike discharge. The activation induced by IBS supernatants was inhibited by histamine receptor (H1-H3) antagonists, 5-HT3 receptor antagonist, and protease inhibition. Serotonin, histamine and tryptase levels in supernatants correlated with the spike discharge induced by the supernatants. Mast cells density as well as histamine and tryptase levels in supernatants were higher in IBS than in controls.

CONCLUSIONS

Mediators released from mucosal biopsies of IBS patients can activate human submucosal neurons. The activation required histamine, serotonin and proteases but was not associated with IBS subtype. Altered signaling between mucosa and the enteric nervous system might be involved in IBS pathogenesis.

Cryptosporidium parvum isolate-dependent postinfectious jejunal hypersensitivity and mast cell accumulation in an immunocompetent rat model

Cryptosporidium spp. are a cause of self-limited diarrhea in immunocompetent hosts. In immunocompetent rats, Cryptosporidium parvum infection induced digestive hypersensitivity, a key pathophysiological factor in functional digestive disorders such as irritable bowel syndrome (IBS). In such a rat model, we sought to document whether jejunal hypersensitivity depends on C. parvum isolate and is associated with a mast cell accumulation. Five-day-old rats were orally administered 10(5) oocysts of either Nouzilly (NoI) or Iowa (IoI) C. parvum isolate. NoI-infected rats exhibited the lowest food intake on days 7 and 14 postinfection (p.i.). On day 7 p.i., small intestine villus atrophy, crypt hyperplasia, and inflammatory cell infiltration were prominent in NoI-infected rats, with higher numbers of Cryptosporidium forms than in IoI-infected rats. Compared to uninfected control rats, jejunal intraepithelial lymphocytes (IELs) were increased only in NoI-infected rats on day 14 p.i. On day 50 p.i., jejunal hypersensitivity to distension was found only in NoI-infected rats; this hypersensitivity is associated with activated mast cell accumulation. The number of mast cells in the jejunal lamina propria was increased from day 36 p.i. in NoI-infected rats and only at day 120 p.i. in IoI-infected rats. Our data suggest that both the severity of infection (weight loss, reduced food intake, villus atrophy, and IEL accumulation) and the onset of a jejunal hypersensitivity after infection in association with an activated mast cell accumulation are isolate dependent and related to NoI infection. This cryptosporidiosis rat model is a relevant model for the study of underlying mechanisms of postinfectious IBS-like symptoms.

The role of diet in symptoms of irritable bowel syndrome in adults: a narrative review

This review summarizes what is known about the effect of diet on irritable bowel syndrome (IBS) symptoms emphasizing data from randomized, controlled clinical trials. Studies suggest that IBS symptoms in one quarter of patients may be caused or exacerbated by one or more dietary components. Recent studies indicate that a diet restricted in fermentable, poorly absorbed carbohydrates, including fructose, fructans (present in wheat and onions), sorbitol, and other sugar alcohols is beneficial, but confirmatory studies are needed. Despite a long history of enthusiastic use, fiber is marginally beneficial. Insoluble fiber may worsen symptoms. Some patients with IBS, especially those with constipation, will improve with increased intake of soluble fiber. Prebiotic fibers have not been adequately tested. Daily use of peppermint oil is effective in relieving IBS symptoms. The usefulness of probiotics in the form of foods such as live-culture yogurt and buttermilk for IBS symptoms is not established. In clinical practice, it is very difficult to establish that a patient's symptoms result from an adverse reaction to food. A double blind placebo-controlled food challenge is the most reliable method, but it is not suitable for routine clinical use. A modified exclusion diet and stepwise reintroduction of foods or trials of eliminating classes of food may be useful.

The clinical course of postinfectious irritable bowel syndrome: a five-year follow-up study

OBJECTIVES

Irritable bowel syndrome (IBS) is a common disorder seen in general practice. Bacterial gastroenteritis has been known to be a risk factor for IBS. We investigated the clinical course, risk factors, and prognosis of postinfectious IBS (PI-IBS) 5 years after Shigella infection.

METHODS

We recruited 153 individuals and used a questionnaire to investigate their current bowel habits. We also looked for the presence of other functional bowel disorders (FBDs). The Shigella-exposed group consisted of hospital employees and medical students who experienced abdominal pain, diarrhea, or fever during the shigellosis outbreak and whose stool culture revealed Shigella sonnei. The control group consisted of age-matched and sex-matched subjects who corresponded fairly well with patients, considering that they were enrolled from the same hospital and were not infected.

RESULTS

Complete data were obtained from 119 individuals who were divided into the Shigella-exposed group (59) and the control group (60). In the Shigella-exposed group, 3 patients had IBS before infection (previous IBS) and 6 out of 13 cases of PI-IBS after 3 years showed persistent IBS after 5 years. Five out of 11 PI-IBS patients (45.5%, 2 excluded), 3 out of 6 previous IBS patients (50%) in the Shigella-exposed group, and 7 out of 11 previous IBS patients (63.6%) in the control group recovered after 5 years (P>0.05). Five cases in the Shigella-exposed group and 3 in the control group developed new cases of IBS after 5 years. The prevalence of PI-IBS after 5 years in the previous FBD groups was 63.6%, whereas the prevalence of PI-IBS without a history of FBDs was 36.4% (P<0.05). There were no significant differences among the other risk factors in each group.

CONCLUSIONS

About half of PI-IBS and previous IBS patients with or without infection recover over 5 years. Previous IBS and FBDs are risk factors of PI-IBS after 5 years. We suggest that our results support the understanding of the clinical course and prognosis of PI-IBS.

Probiotics and gastrointestinal infections

Gastrointestinal infections are a major cause of morbidity and mortality worldwide, particularly in developing countries. The use of probiotics to prevent and treat a variety of diarrheal diseases has gained favor in recent years. Examples where probiotics have positively impacted gastroenteritis will be highlighted. However, the overall efficacy of these treatments and the mechanisms by which probiotics ameliorate gastrointestinal infections are mostly unknown. We will discuss possible mechanisms by which probiotics could have a beneficial impact by enhancing the prevention or treatment of diarrheal diseases.

Prevalence of recurring symptoms after infection with Giardia lamblia in a non-endemic area

OBJECTIVE

Investigation of the clinical course of infection with Giarda lamblia after a large outbreak in an area where Giardia is not endemic in humans.

DESIGN

A cohort of patients from primary healthcare with clinically defined giardiasis was investigated by retrospectively analysing data from the patients' medical records.

SETTING

Urban primary healthcare setting in Bergen, Norway.

SUBJECTS

From a population (n = 7100) assigned to two general practice clinics located in the outbreak area 134 patients met the inclusion criteria of at least one of the following: typical symptoms for at least one week, detection of Giarda lamblia in stool samples, or receiving a specific diagnosis. Of these, 119 gave consent to take part in the study.

MAIN OUTCOME MEASURES

Proportion of patients with clinical giardiasis identified by detection of parasites in stool samples. Proportion of patients with prolonged disease and recurring symptoms.

RESULTS

A positive test for Giardia lamblia was found in 55% (66/119) of the patients. Specific treatment was given to 89 patients, and after treatment 36% (32/89) returned to their doctor because they experienced recurring symptoms. Compared with those not returning a significantly higher proportion of this group had seen their GP for other GI complaints in the previous two years.

CONCLUSION

Laboratory-based diagnosis missed a substantial number of patients falling sick with giardiasis during the outbreak. One-third of the patients experienced recurring symptoms after treatment, and there was an association between previous gastrointestinal complaints and recurrence of symptoms.

Review article: the psychoneuroimmunology of irritable bowel syndrome--an exploration of interactions between psychological, neurological and immunological observations

BACKGROUND

The pathogenesis of irritable bowel syndrome (IBS) is founded on interactive mechanisms. Disentangling these processes is a prerequisite for the development of effective drug therapy.

AIM

To identify the interaction between the various factors implicated in IBS.

METHODS

Articles pertaining to IBS pathogenesis focusing on psychoneuroimmunology were identified using following search terms: IBS, animal models, microbiota, probiotics, immunology, visceral hypersensitivity, imaging, psychology and visceral pain.

RESULTS

Cerebral imaging using MRI and proton emission tomography scanning has revealed differential regional cerebral activation, whereas stimuli induced activation has been captured by both MRI and cortical evoked potentials. At the peripheral neurological level, the concept of visceral hypersensitivity has been challenged as perhaps representing psychological traits with symptom over-reporting or hyper-vigilance. Gut mucosal immunology is thought to be relevant with immunological changes reflected as peripheral blood cytokine level changes. Molecular technology advances suggest a role for microbiota by activating the gut immunological system. These interactions have been examined in IBS animal models.

CONCLUSIONS

Translation of animal model findings to humans is needed to link the various psychological, neurological and immunological changes noted in IBS. This analysis may identify patient sub-groups, which will ultimately be critical for drug testing to be focused accordingly.

Is irritable bowel syndrome an inflammatory disorder?

Histopathologic data demonstrate low-grade mucosal inflammation in a subset of patients with irritable bowel syndrome (IBS). This inflammatory infiltrate is mainly represented by increased numbers of T lymphocytes and mast cells lying in the lamina propria. The close apposition of immunocytes to gut nerves supplying the mucosa provides a basis for neuroimmune cross-talk, which may explain gut sensorimotor dysfunction and related symptoms in patients with IBS. A previous gastroenteritis (due to Campylobacter jejuni, Salmonella, Shigella, Escherichia coli, and, likely, viruses) is now an established etiologic factor for IBS (hence, postinfectious IBS). Other putative causes, such as undiagnosed food allergies, genetic abnormalities, stress, or bile acid malabsorption, may also promote and maintain a low-grade mucosal inflammation in IBS. The identification of mucosal inflammation in IBS has pathophysiologic implications and paves the way for novel therapeutic options.

Functional gastrointestinal disorders and the potential role of eosinophils

The eosinophil-mast cell-neural pathway may be important in the pathophysiology of functional gastrointestinal disorders characterized by unexplained abdominal pain, disordered defecation, or meal-related discomfort. There is evidence that duodenal eosinophils are increased in functional dyspepsia, whereas mast cells are increased in the lower gut in irritable bowel syndrome, directly supporting a role for a hypersensitivity-type reaction in these disorders. The trigger may be a pathogen, food, or other allergen in the gut mucosa. This trigger may evoke eosinophils, mast cells, and other components to cascade to up-regulate serotonin release, with modulation of the enteric and central nervous systems, creating a vicious cycle. If correct, this theory suggests treatment should specifically target the eosinophil-mast cell pathway.

Lactulose breath test results in patients with persistent abdominal symptoms following Giardia lamblia infection

OBJECTIVE

Bacterial overgrowth has been implicated in the pathogenesis of irritable bowel syndrome (IBS). The objective of this study was to investigate whether post-infectious IBS following Giardia lamblia infection is related to intestinal bacterial overgrowth, as diagnosed by the lactulose breath test (LBT).

MATERIAL AND METHODS

Seventy-seven patients with persistent gastrointestinal complaints related to a recent outbreak of G. lamblia infection were included in the study. Despite one or several courses of treatment with metronidazole during the previous months, 23 of the patients were still stool positive for G. lamblia, whereas the remaining 54 patients had cleared the infection. All patients and 42 healthy volunteers underwent a LBT with 10 g lactulose, and their customary and post-LBT abdominal symptoms were scored.

RESULTS

Ninety-five percent of the patients had IBS. Lactulose-induced hydrogen breath excretion was not significantly different in patients and controls. Customary and post-LBT symptoms were abnormally high in the patients, irrespective of both G. lamblia infection status and LBT results. Furthermore, lactulose challenge replicated the patients' customary complaints in 70% of the patients.

CONCLUSIONS

Gastrointestinal complaints in patients with persistent or cleared giardiasis were unrelated to hydrogen breath excretion after lactulose challenge. Post-giardiasis IBS cannot be ascribed to intestinal bacterial overgrowth, as diagnosed by LBT.

Concept of Crohn's disease being conditioned by four main components, and irritable bowel syndrome being an incomplete Crohn's disease

Several mechanisms have been proposed for the development of Crohn's disease. Evidence in favour of a unifying 4-component concept to explain the development of Crohn's disease is presented. The four components are a genetic predisposition to an increased intestinal permeability, the key and initial triggering factor being an oral-pharyngeal bacterium that increases the mucosal permeability of the small intestine with only a minimal inflammatory reaction, an adherent-invasive strain of Escherichia coli that penetrates the mucosa and causes an acute inflammatory reaction in the intestinal wall, and finally a secondary invasion of bacteria causing the chronic inflammatory characteristics. Irritable bowel syndrome (IBS) is a functional bowel disorder with intermittent symptoms of varying intensity. Clinically, there is evidence to suggest a link between IBS patients with diarrhoea and patients with Crohn's disease. The common denominator and initial trigger for IBS with diarrhoea and Crohn's disease seems to be an increased small intestinal permeability, probably caused by an oral-pharyngeal bacterial strain. The important missing factor in IBS patients seems to be the adherent-invasive strain of E. coli in the proximal colon, causing the acute inflammatory process in patients with Crohn's disease. IBS with diarrhoea can then be looked upon as an incomplete Crohn's disease.

Updates on treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent gastrointestinal disorder characterized by abdominal pain and discomfort in association with altered bowel habits. It is estimated to affect 10%-15% of the Western population, and has a large impact on quality of life and (in)direct healthcare costs. IBS is a multifactorial disorder involving dysregulation within the brain-gut axis, and it is frequently associated with gastrointestinal motor and sensory dysfunction, enteric and central nervous system irregularities, neuroimmune dysregulation, and post-infectious inflammation. As with other functional medical disorders, the treatment for IBS can be challenging. Conventional therapy for those with moderate to severe symptoms is largely unsatisfactory, and the development of new and effective drugs is made difficult by the complex pathogenesis, variety of symptoms, and lack of objective clinical findings that are the hallmark of this disorder. Fortunately, research advances over the past several decades have provided insight into potential mechanisms responsible for the pathogenesis of IBS, and have led to the development of several promising pharmaceutical agents. In recent years there has been much publicity over several of these new IBS medications (alosetron and tegaserod) because of their reported association with ischemic colitis and cardiovascular disease. While these agents remain available for use under restricted prescribing programs, this highlights the need for continued development of safe and effective medication for IBS. This article provides a physiologically-based overview of recently developed and frequently employed pharmaceutical agents used to treat IBS, and discusses some non-pharmaceutical options that may be beneficial in this disorder.