Amelioration of murine colitis by feeding a solution of lysed Escherichia coli

Intravenous injection of endogenous microbial components abrogates DSS-induced colitis

BACKGROUND

The etiology of inflammatory bowel diseases (IBD) is largely unknown, but appears to be perpetuated by uncontrolled responses to antigenic components of the endogenous flora. Tolerance to antigenic stimulation can be achieved by exposure to a given antigen in high amounts (high dose tolerance). Colitis induced by feeding of Dextran Sodium Sulfate (DSS) is an often-used animal model mimicking clinical and histological features of human IBD.

AIMS

We investigated whether treatment with high doses of endogenous bacterial components can affect the response to these antigenic components and thus impact the course of the inflammatory response induced by DSS.

METHODS

129/SvEv mice were injected intravenously in the tail vein with lysates prepared from fecal material of conventionally-raised mice. Control mice received a solution of bacterial antigen-free lysates prepared from fecal material of germ-free mice. Seven days later, colitis was induced in these mice by introducing DSS (3.5%) in the drinking water for 5 days. Onset and course of the inflammatory response was monitored by assessment of weight loss. Mice were sacrificed at day 7 post colitis induction and tested for histopathologic injury, intestinal cytokine release, and systemic response to bacterial antigens.

RESULTS

Intravenous injection with fecal lysates reduced intestinal and antigen-stimulated systemic pro-inflammatory cytokine release and prevented DSS-induced weight loss and intestinal injury.

CONCLUSION

Pretreatment with high amount of endogenous bacterial components has a profound tolerogenic effect on the systemic and mucosal immune responses resulting in reduced intestinal inflammation and abrogates colitis-induced weight loss.

Nitric oxide as a target of complementary and alternative medicines to prevent and treat inflammation and cancer

Nitric oxide (NO) and associated reactive nitrogen species (RNS) are involved in many physiological functions. There has been an ongoing debate to whether RNS can inhibit or perpetuate chronic inflammation and associated carcinogenesis. Although the final outcome depends on the genetic make-up of its target, the surrounding microenvironment, the activity and localization of nitric oxide synthase (NOS) isoforms, and overall levels of NO/RNS, evidence is accumulating that in general, RNS drive inflammation and cancers associated with inflammation. To this end, many complementary and alternative medicines (CAMs) that work in chemoprevention associated with chronic inflammation, are inhibitors of excessive NO observed in inflammatory conditions. Here, we review recent literature outlining a role of NO/RNS in chronic inflammation and cancer, and point toward NO as one of several targets for the success of CAMs in treating chronic inflammation and cancer associated with this inflammation.

Quality of life in chronic pancreatitis

In an era such as the present one in which there is a high demand for health services with the associated pressure of controlling spending, health care organizations are concerned about the cost-effectiveness of quality improvement interventions. On the other hand, the impact of the disease and the treatment on the patient’s overall well-being and functioning has become a topic of growing interest not only in clinical research but also in practice. The clinical evaluation of the benefits of specific treatments for chronic, debilitating and incurable diseases should increasingly include formal assessment of patient activity and well-being. Thus, health-related quality of life as subjectively perceived by the patient, is becoming a major issue in the evaluation of any therapeutic intervention, mainly in patients with chronic or difficult diseases where the aim of the intervention is to keep patients either symptom-free and capable of living in the community for a long time or to reduce the discomfort caused by the disease. In this paper, we review the current knowledge on the quality of life assessment in chronic pancreatitis patients.

Probiotics and prebiotics in chronic inflammatory bowel diseases

The prokaryotic and eukaryotic cells of the colon exist in a highly complex, but harmonious relationship. Disturbances in this remarkable symbiosis can result in the development of inflammatory bowel diseases (IBD). Although the etiology of IBD is not entirely understood, it is known that the chronic inflammation of Crohn’s disease, ulcerative colitis and chronic pouchitis are a result of an overly aggressive immune response to the commensal intestinal flora in genetically susceptible hosts. Recent studies have enhanced our ability to understand the interaction between the host and its intestinal microflora and the role the microflora plays in maintaining intestinal homeostasis. As we begin to understand the benefits conferred to the intestine by the microflora, the notion of modifying the composition of the bacterial load to improve human health has arisen. A significant body of research now exists investigating the role of probiotics and prebiotics in ameliorating chronic intestinal inflammation. This article will begin with an overview of the role of the commensal microflora in maintaining mucosal immune homeostasis, and how a dysregulated immune response to the intestinal microflora results in IBD. This will be followed by a summary of the use of probiotics and prebiotics in experimental and human IBD.

Role of interleukin (IL-10) in probiotic-mediated immune modulation: an assessment in wild-type and IL-10 knock-out mice

While the impact of Bifidobacterium infantis 35624 and other probiotics on cytokines has been shown in established colitis, the effects of B. infantis consumption in pre-inflammation of interleukin (IL)-10 knock-out (KO) mice and on the wild-type (WT) C57Bl/6 mice have not been well demonstrated. The objective of this study was to examine cytokine responses in mucosal and systemic lymphoid compartments of IL-10 KO mice early in disease and to compare with control WT mice. Mice were fed B. infantis or placebo for 5 weeks and culled prior to the onset of chronic intestinal inflammation (12-14 weeks). The spleen, Peyer's patches and intestinal mucosa were removed and stimulated with various bacterial stimuli. Cytokine levels were measured by enzyme-linked immunosorbent assay. While basal intestinal and systemic cytokine profiles of WT and IL-10 KO mice were similar, transforming growth factor (TGF)-beta was reduced in the spleen of IL-10 KO mice. Following probiotic consumption, interferon (IFN)-gamma was reduced in the Peyer's patch of both WT and IL-10 KO mice. Alterations in IFN-gamma in the Peyer's patches of WT mice (enhancement) versus IL-10 KO (reduction) were observed following in vitro stimulation with salmonella. Differential IL-12p40, CCL2 and CCL5 responses were also observed in IL-10 KO mice and WT mice. The cytokine profile of IL-10 KO mice in early disease was similar to that of WT mice. The most pronounced changes occurred in the Peyer's patch of IL-10 KO mice, suggesting a probiotic mechanism of action independent of IL-10. This study provides a rationale for the use of B. infantis 35624 for the treatment of gastrointestinal inflammation.

The effect of vitamin A supplementation on the intestinal immune response in Mexican children is modified by pathogen infections and diarrhea

Vitamin A supplementation has consistently reduced infant mortality and the severity of pathogen-induced diarrhea. The mechanism by which vitamin A modulates the mucosal immune response to produce these effects remains poorly defined. To address this issue, stools collected during the summer months from 127 Mexican children 5-15 mo old enrolled in a larger, randomized, double-blind, placebo-controlled, vitamin A supplementation trial were screened for interleukin (IL)-4, IL-6, interferon-gamma (IFN-gamma), and gastrointestinal pathogens. Fecal cytokine values were categorized into 3 levels (undetectable, <median, > or =median). Multinomial regression models were used to determine the probability that vitamin A-supplemented children had higher categorical values of a cytokine than children in the placebo group. Differences in categorical values were also analyzed after stratification by gastrointestinal pathogen infections and diarrheal symptoms. Overall, fecal cytokine categorical levels did not differ between children randomized to the 2 arms. Vitamin A-supplemented children infected with enteropathogenic E. coli (EPEC) had reduced IL-4 and IFN-gamma levels [odds ratio (OR) = 0.3, 95% CI 0.13-0.67 and OR = 0.34, 95% CI 0.14-0.83, respectively] compared with children in the placebo group. Vitamin A-supplemented children had increased IL-4 levels when infected with A. lumbricoides (OR = 12.06, 95% CI 0.95-153.85). In contrast, IL-4 levels increased (OR = 2.14, 95% CI 0.94-4.87) and IFN-gamma levels decreased (OR = 0.51, 95% CI 0.26-0.99) among vitamin A-supplemented children with diarrhea compared with children in the placebo group. These findings suggest that the regulation of the mucosal immune response by vitamin A may depend on the type of enteric pathogen infecting the child and the presence of clinical symptoms.

Place of probiotics

PURPOSE OF REVIEW

This review reports on the recent progress understanding mechanisms of action and clinical applications of probiotics.

RECENT FINDINGS

New insights on regulating mechanisms of intestinal commensal bacteria to prevent and treat different gastrointestinal diseases have been reported. Some probiotics, though not all, exert beneficial effects by modulating the mucosal barrier function and immune activity. It seems that a combination of different probiotics is more effective than a single strain. It was demonstrated that not only viable bacteria administered to the intestinal tract but also isolated probiotic DNA is active, even if injected subcutaneously. There is reasonable evidence to recommend probiotics in infectious diarrhoea for prevention and treatment (mainly in children) and to prevent antibiotic-induced gastrointestinal side effects. Furthermore, probiotics are effective in maintaining remission in ulcerative colitis and preventing and treating pouchitis. Promising positive effects were published in major surgery patients (gastric resection, pancreatic resection, liver transplantation) and in severe necrotising acute pancreatitis.

SUMMARY

Increasing knowledge on probiotics is exciting, but in the near future it must be defined which probiotics (single strains or a combination) are most effective in specific diseases. Well-designed, randomized clinical trials are still required to further define the role of probiotics as preventive and therapeutic agents.

Roles of Glutathione in dextran sodium sulphate-induced colitis in mice

AIM: To investigate the expression of glutathione (GSH) in dextran sodium sulphate(DSS)-induced colitic mucosa and its relationship with cytokine secretion as well as mucosal injury.

METHODS: BALB/c mice in DSS group (n = 10) were fed with 50 g/L DSS to induce experimental colitis and those in normal controls (n = 10) were fed with distilled water. All the mice were killed after 7 days. The pathological changes of the colonic tissues were examined while immunohi-stochemstry was performed with GSH1 antibody to determine the GSH expression. ELISA was used to detect the expression of IL-4 and IFN-γ.

RESULTS: The manifestations of acute colitis such as weight decrease, diarrhea and bloody stool appeared in mice of DSS group. focal crypt lesionsPathologically, focal crypt distortion, granulocyte and macrophage invasion were observed. The level of GSH in DSS group was significantly lower than that in control group (20.6 vs 3.14±1.0, t = 3.95, P = 0.01), whereas the expression of IL-4 was marked higher (38.7±4.7 vs 28.7±6.7, t = 3.16, P = 0.009). The content of IFN-γ was decreased in DSS group (P>0.05).

CONCLUSION: Low expression of GSH is related to the increase of IL-4, decrease of IFN-γ and mucosal injury in DSS-induced colitis in mice.

Escherichia coli Nissle 1917 distinctively modulates T-cell cycling and expansion via toll-like receptor 2 signaling

Although the probiotic Escherichia coli strain Nissle 1917 has been proven to be efficacious for the treatment of inflammatory bowel diseases, the underlying mechanisms of action still remain elusive. The aim of the present study was to analyze the effects of E. coli Nissle 1917 on cell cycling and apoptosis of peripheral blood and lamina propria T cells (PBT and LPT, respectively). Anti-CD3-stimulated PBT and LPT were treated with E. coli Nissle 1917-conditioned medium (E. coli Nissle 1917-CM) or heat-inactivated E. coli Nissle 1917. Cyclin B1, DNA content, and caspase 3 expression were measured by flow cytometry to assess cell cycle kinetics and apoptosis. Protein levels of several cell cycle and apoptosis modulators were determined by immunoblotting, and cytokine profiles were determined by cytometric bead array. E. coli Nissle 1917-CM inhibits cell cycling and expansion of peripheral blood but not mucosal T cells. Bacterial lipoproteins mimicked the effect of E. coli Nissle 1917-CM; in contrast, heat-inactivated E. coli Nissle 1917, lipopolysaccharide, or CpG DNA did not alter PBT cell cycling. E. coli Nissle 1917-CM decreased cyclin D2, B1, and retinoblastoma protein expression, contributing to the reduction of T-cell proliferation. E. coli Nissle 1917 significantly inhibited the expression of interleukin-2 (IL-2), tumor necrosis factor alpha, and gamma interferon but increased IL-10 production in PBT. Using Toll-like receptor 2 (TLR-2) knockout mice, we further demonstrate that the inhibition of PBT proliferation by E. coli Nissle 1917-CM is TLR-2 dependent. The differential reaction of circulating and tissue-bound T cells towards E. coli Nissle 1917 may explain the beneficial effect of E. coli Nissle 1917 in intestinal inflammation. E. coli Nissle 1917 may downregulate the expansion of newly recruited T cells into the mucosa and limit intestinal inflammation, while already activated tissue-bound T cells may eliminate deleterious antigens in order to maintain immunological homeostasis.

Escherichia coli Nissle 1917 distinctively modulates T-cell cycling and expansion via toll-like receptor 2 signaling

Although the probiotic Escherichia coli strain Nissle 1917 has been proven to be efficacious for the treatment of inflammatory bowel diseases, the underlying mechanisms of action still remain elusive. The aim of the present study was to analyze the effects of E. coli Nissle 1917 on cell cycling and apoptosis of peripheral blood and lamina propria T cells (PBT and LPT, respectively). Anti-CD3-stimulated PBT and LPT were treated with E. coli Nissle 1917-conditioned medium (E. coli Nissle 1917-CM) or heat-inactivated E. coli Nissle 1917. Cyclin B1, DNA content, and caspase 3 expression were measured by flow cytometry to assess cell cycle kinetics and apoptosis. Protein levels of several cell cycle and apoptosis modulators were determined by immunoblotting, and cytokine profiles were determined by cytometric bead array. E. coli Nissle 1917-CM inhibits cell cycling and expansion of peripheral blood but not mucosal T cells. Bacterial lipoproteins mimicked the effect of E. coli Nissle 1917-CM; in contrast, heat-inactivated E. coli Nissle 1917, lipopolysaccharide, or CpG DNA did not alter PBT cell cycling. E. coli Nissle 1917-CM decreased cyclin D2, B1, and retinoblastoma protein expression, contributing to the reduction of T-cell proliferation. E. coli Nissle 1917 significantly inhibited the expression of interleukin-2 (IL-2), tumor necrosis factor alpha, and gamma interferon but increased IL-10 production in PBT. Using Toll-like receptor 2 (TLR-2) knockout mice, we further demonstrate that the inhibition of PBT proliferation by E. coli Nissle 1917-CM is TLR-2 dependent. The differential reaction of circulating and tissue-bound T cells towards E. coli Nissle 1917 may explain the beneficial effect of E. coli Nissle 1917 in intestinal inflammation. E. coli Nissle 1917 may downregulate the expansion of newly recruited T cells into the mucosa and limit intestinal inflammation, while already activated tissue-bound T cells may eliminate deleterious antigens in order to maintain immunological homeostasis.

Quality of life in patients with chronic pancreatitis

INTRODUCTION

Health-related quality of life is becoming a major issue in the evaluation of any therapeutic intervention in patients with chronic or hard to cure diseases.

AIMS

To assess the quality of life in patients with chronic pancreatitis, the majority of whom have had the disease for a long time, and to evaluate which factors linked to the disease are able to influence the quality of life.

SUBJECTS AND METHODS

A total of 190 consecutive patients (157 males, 33 females; mean age 58.6+/-12.7 years, range 18-92 years) with proven chronic pancreatitis were enrolled. The SF-36 questionnaire was used for assessing the health-related quality of life.

RESULTS

The z-scores of the eight domains of the patients with chronic pancreatitis were significantly negative indicating an overall impairment of the quality of life when compared to the Italian normative sample. Pancreatic pain was the unique clinical variable able to significantly impair all eight domains of the SF-36, while Wirsung dilation and diabetes were negatively related to some physical and mental domains. The body mass index was the unique variable positively related with some SF-36 domains.

CONCLUSIONS

Pain may be considered the most important factor affecting the quality of life of chronic pancreatitis patients; moreover, alimentary and metabolic factors deserve more attention in improving the quality of life of these subjects.

Ameliorative effect of IDS 30, a stinging nettle leaf extract, on chronic colitis

BACKGROUND AND AIMS

Anti-TNF-alpha antibodies are very effective in the treatment of acute Crohn's disease, but are limited by the decline of their effectiveness after repeated applications. The stinging nettle leaf extract, IDS 30, is an adjuvant remedy in rheumatic diseases dependent on a cytokine suppressive effect. We investigated the effect of IDS 30 on disease activity of murine colitis in different models.

METHODS

C3H.IL-10-/- and BALB/c mice with colitis induced by dextran sodium sulphate (DSS) were treated with either IDS 30 or water. Mice were monitored for clinical signs of colitis. Inflammation was scored histologically, and faecal IL-1beta and mucosal cytokines were measured by ELISA. Mononuclear cell proliferation of spleen and Peyer's patches were quantified by 3H-thymidine.

RESULTS

Mice with chronic DSS colitis or IL-10-/- mice treated with IDS 30 clinically and histologically revealed significantly (p < 0.05) fewer signs of colitis than untreated animals. Furthermore, faecal IL-1beta and mucosal TNF-alpha concentrations were significantly lower (p < 0.05) in treated mice. Mononuclear cell proliferation after stimulation with lipopolysaccharide was significantly (p < 0.001) reduced in mice treated with IDS 30.

CONCLUSIONS

The long-term use of IDS 30 is effective in the prevention of chronic murine colitis. This effect seems to be due to a decrease in the Th1 response and may be a new therapeutic option for prolonging remission in inflammatory bowel disease.

Long-term clinical outcome after endoscopic pancreatic ductal drainage for patients with painful chronic pancreatitis

BACKGROUND & AIMS

Endotherapy for patients with painful chronic pancreatitis (CP) gives early and midterm clinical results comparable with those of conventional surgery. The authors evaluated long-term clinical outcome after endoscopic pancreatic ductal drainage, focusing on pain and pancreatic endocrine/exocrine functions.

METHODS

Of 110 patients with painful CP endoscopically treated between October 1987 and December 1989, 56 long-surviving patients were followed-up for 14.4 years (SD, .6 y); 40 patients died and 14 patients were lost to follow-up evaluation. Technical results included decreased ductal dilation and stone clearance. Clinical results included the rate of hospitalizations for pain before and after endotherapy, the need for surgery, the course of endocrine/exocrine insufficiencies, and late mortality.

RESULTS

Complete or partial technical success initially was obtained in 48 of 56 long-surviving patients. Long-term clinical success (< or =5 hospitalizations for pain during follow-up evaluation, without surgery) was obtained for 37 of 56 patients. At a mean follow-up time of 14.4 years, 44 patients had avoided surgery and the annual rate of hospitalizations for pain decreased significantly (before endotherapy: 0.98 [+/-1.36] vs 0.40 [+/-0.51] for the 3 years thereafter vs 0.14 [+/-0.22] for the last 11 years of follow-up evaluation; P < .001). Short duration of disease before initial therapy and absence of smoking at the last follow-up evaluation were associated with long-term clinical success.

CONCLUSIONS

Endotherapy provides long-term benefits for about two thirds of patients with painful CP. Good clinical outcome was associated with cessation or absence of smoking, whereas alcohol abuse increased the risks for diabetes mellitus, steatorrhea, and mortality.

Increased incidence of inflammatory bowel disease: the price of the decline of infectious burden?

PURPOSE OF REVIEW

It is now apparent that the increase in the incidence of autoimmune and allergic diseases in Western countries is explained by the decrease in infections. The question is posed to determine whether a similar explanation can be proposed for the increased incidence of inflammatory bowel disease.

RECENT FINDINGS

Studies performed in murine experimental models of inflammatory bowel disease have shown that colitis onset can be prevented by bacteria, bacterial extracts, or helminths. Particular interest was given to probiotics (either live or killed), which protect from disease in a toll-like receptor 9 dependent fashion. This protective effect involves regulatory cytokines as indicated by in vitro studies on human inflamed colonic cells. At the clinical level, there is strong suggestion but still limited proof that probiotics improve inflammatory bowel disease through immunoregulatory mechanisms.

SUMMARY

Converging clinical and experimental data strongly suggest the protective nonspecific role of infections on inflammatory bowel disease independently from the triggering role of some specific bacteria. The extension to inflammatory bowel disease of the hygiene hypothesis opens new therapeutic perspectives including the revisiting of probiotics and other forms of exposure to bacteria or parasite components.

Refined histopathologic scoring system improves power todetect colitis QTL in mice

Induction of colitis in mice by a targeted mutation in the I110 gene is inbred strain dependent. C3H/ HeJBir (C3H) mice are colitis susceptible while C57BL/6J (B6) mice are resistant. Identification of quantitative trait loci (QTL) determining the differential strain responsiveness requires histopathologic scoring of multiple lesion subphenotypes in both cecum and colon. Here we show that ability to detect a major C3H-derived QTL on Chr 3 (cytokine deficiency-induced colitis susceptibility 1, Cdcs1) was critically dependent upon the degree of refinement of the histopathologic scoring system. QTL mapping was performed using a first-back-cross population of interleukin-10-deficient mice and applying two different grading systems to assess lesion subphenotypes. The same histological specimens were scored by two independent pathologists using either a very detailed scoring system for four subphenotypes developed at The Jackson Laboratory (TJL) or a simpler scoring system developed at the Hannover Medical School (MHH). The more detailed TJL subphenotyping protocol increased power to identify Cdcs1 (a maximum LOD score of 4.28 versus a LOD score of 1.77 when using the abbreviated MHH subphenotyping scoring system). This study shows that for QTL mapping in a mouse model of colitis, in which histology represents the gold standard for phenotyping, ability to detect linkage is critically dependent upon the degree of refinement adopted for separately scoring the multiple histopathologic lesions comprising this complex phenotype.

Surgical and interventional treatment of chronic pancreatitis

The management of patients with chronic pancreatitis (CP) remains a challenging problem. Main indications for surgery are intractable pain, suspicion of malignancy, and involvement of adjacent organs. The main goal of surgical treatment is improvement of patient quality of life. The surgical treatment approach usually involves proximal pancreatic resection, but lateral pancreaticojejunal drainage may be used for large-duct disease. The newer duodenum-preserving head resections of Beger and Frey provide good pain control and preservation of pancreatic function. Thoracoscopic splanchnicectomy and the endoscopic approach await confirmatory trials to confirm their efficiency in the management of CP. Common bile duct obstruction is addressed by distal Roux-en-Y choledochojejunostomy but when combined with dudodenal obstruction must be treated by pancreatic head resection. Pancreatic ascites due to disrupted pancreatic duct should be treated by internal drainage. The approach to CP is multidisciplinary, tailoring the various therapeutic options to meet each individual patient's needs.

New developments in experimental models of inflammatory bowel disease

PURPOSE OF REVIEW

To consider new data and directions coming from experimental models of inflammatory bowel diseases.

RECENT FINDINGS

Advances are discussed in the areas of microbial-host interactions in the intestine, the role of cytokines like IL-23, chemokines like IP-10, and various costimulatory molecules in disease pathogenesis. Multiple regulatory cells have been identified as well as the mechanisms they use to inhibit pathogenic responses to the microbiota in the intestine. New data is available on how the intestine heals after inflammatory insults.

SUMMARY

These data are providing fundamental insights into the pathogenesis of IBD and thus are forming the basis of new therapeutic approaches, many of which will be translated to the clinic in the near future.

Update in inflammatory bowel disease pathogenesis

PURPOSE OF REVIEW

During the last few years, significant advances have been achieved in the understanding of the pathogenesis of inflammatory bowel disease (IBD). By gaining new insights, paradigms that seemed to be a safe basis of our knowledge on IBD pathogenesis have recently become doubtful. This review discusses and summarizes the most recent developments.

RECENT FINDINGS

Important new insights have been gained into the function of caspase-activating and recruitment domain-15 (CARD15)/NOD2, the first cloned susceptibility gene for Crohn disease (CD). New data on CARD15/NOD2 function and nuclear factor-kappaB activation indicate that an inflammatory reaction of the intestinal mucosa as a response of the innate immune system may be necessary for the maintenance of gut homeostasis. CD may therefore be seen as a defective immune response, no longer only as hyperresponsiveness of the mucosal immune system. Data on CARD15/NOD2 expression suggest that macrophages and epithelial cells could be the site of a primary pathophysiologic defect, and T-cell activation might just be a secondary effect inducing chronification of the inflammation, perhaps as a backup mechanism to a defective innate immunity. In addition to CARD15/NOD2, there are additional "innate" pathways by which commensal and pathogenic bacteria can directly interact with cells of the intestinal mucosa (eg, toll-like receptors). The "germ concept" and the "genetic concept" of IBD pathophysiology are converging.

SUMMARY

New findings are changing our concepts of the pathogenesis of IBD. The innate immune system, early responses to bacterial products, and the modulation of T-cell responses are important aspects that are reviewed.

Probiotics and prebiotics in gastrointestinal disorders

PURPOSE OF REVIEW

This review summarizes the clinical efficacy of probiotics and prebiotics in gastrointestinal disorders and examines the mechanisms of action related to their therapeutic effect.

RECENT FINDINGS

The demonstration that immune and epithelial cells can discriminate between different microbial species has extended the known mechanism(s) of action of probiotics beyond simple barrier and antimicrobial effects. It has also confirmed that probiotic bacteria modulate mucosal and systemic immune activity and epithelial function. The progressive unraveling of these mechanisms of action has led to new credence for the use of probiotics and prebiotics in clinical medicine. Level I evidence now exists for the therapeutic use of probiotics in infectious diarrhea in children, recurrent Clostridium difficile-induced infections and postoperative pouchitis. Level II evidence is emerging for the use of probiotics in other gastrointestinal infections, prevention of postoperative bacterial translocation, irritable bowel syndrome, and in both ulcerative colitis and Crohn disease. Nevertheless, one consistent feature has emerged over the past year: Not all probiotic bacteria have similar therapeutic effects. Future clinical trials will need to incorporate this fact into trial planning and design.

SUMMARY

The use of probiotics and prebiotics as therapeutic agents for gastrointestinal disorders is rapidly moving into the "mainstream." Mechanisms of action explain the therapeutic effects and randomized; controlled trials provide the necessary evidence for their incorporation into the therapeutic armamentarium.