Two-year combination antibiotic therapy with clarithromycin, rifabutin, and clofazimine for Crohn's disease

Induction of matrix metalloproteinases and TLR2 and 6 in murine colon after oral exposure to Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) is suspected to be a causative agent in Crohn's disease. Recent evidence suggests that MAP can induce the expression of Matrix Metalloproteinases (MMPs), which are the main proteases in the pathogenesis of mucosal ulcerations in inflammatory bowel disease (IBD). Within the present study, we analysed whether oral MAP exposure can induce colonic MMP expression in vivo. In MAP exposed mice MAP and spheroplasts were visualized in intramucosal leukocyte aggregates. MAP exposed mice exhibited a higher colonic expression of Mmp-2, -9, -13, -14, Timp-1, Tlr2, Tlr6, Il-1β, and Tnf-α. Cell clusters of MMP-9 positive cells adjacent to intramucosal leukocyte aggregates and CD45(+) leukocytes were identified as the major cellular sources of MMP-9. Enhanced TLR2 expression was visualized on the luminal side of colonic enterocytes. Although MAP exposure did not lead to macroscopic intestinal inflammation, the observed MAP spheroplasts in intramucosal leukocyte aggregates together with increased colonic expression of toll-like receptors, pro-inflammatory cytokines, and MMPs upon MAP exposure represents a part of the host immune response towards MAP.

Crohn's disease and the mycobacterioses: a quarter century later. Causation or simple association?

It has been more than 25 years since Mycobacterium paratuberculosis was first proposed as an etiologic agent in Crohn's disease based on the isolation of this organism from several patients. Since that time, a great deal of information has been accumulated that clearly establishes an association between M. paratuberculosis and Crohn's disease. However, data are conflicting and difficult to interpret and the field has become divided into committed advocates and confirmed skeptics. This review is an attempt to provide a thorough and objective summary of current knowledge from both basic and clinical research from the views and interpretations of both the antagonists and proponents. The reader is left to draw his or her own conclusions related to the validity of the issues and claims made by the opposing views and data interpretations. Whether M. paratuberculosis is a causative agent in some cases or simply represents an incidental association remains a controversial topic, but current evidence suggests that the notion should not be so readily dismissed. Remaining questions that need to be addressed in defining the role of M. paratuberculosis in Crohn's disease and future implications are discussed.

Medical management of Crohn's disease

INTRODUCTION

The medical approach to Crohn's disease has been modified in recent years thanks to the introduction of new therapies, like biologics. Also, well-designed studies and systematic reviews have allowed better evaluation of the role of old drugs like steroids and immunosuppressors. This review aims to evaluate the recent evidence on the medical approach to Crohn's disease in the different settings of the disease.

AREAS COVERED

Randomized controlled trials and meta-analyses were included in the review. The research on all the studies discussed was based on the Cochrane Library, Medline and Embase, using the following medical subject headings: Crohn's disease, clinical trial, therapy, 5-aminosalicylic acid, steroid, budesonide, immunosuppressant, anti-meta-analysis TNF and biologics.

EXPERT OPINION

In a mild active inflammatory ileocecal disease, budesonide is considered the best approach. The efficacy of aminosalicylates is limited, but a trial that has recently compared aminosalicylates and budesonide has shown that the two drugs are comparable. In a mild colonic disease, sulfasalazine, antibiotics and steroids are effective but the evidence for antibiotics is less clear. The maintenance of remission in this setting is debatable, but sulfasalazine seems the better choice. In a moderate severe ileal and colonic disease, steroids are the best therapy to induce remission. Once remission is reached, immunosuppressors remain today the better choice to maintain the remission. Anti-TNF therapy is indicated in patients intolerant or not responding to steroids and immunosuppressors and in fistulizing Crohn's disease. Early therapy with biologics may be considered in patients with severe disease.

Characterization of the gastrointestinal microbiota in health and inflammatory bowel disease

The enteric bacterial flora play a key role in maintaining health. Inflammatory bowel disease is associated with quantitative and qualitative alterations in the microbiota. Early characterization of the microbiota involved culture-dependent techniques. The advent of metagenomic techniques, however, allows for structural and functional characterization using culture-independent methods. Changes in diversity, together with quantitative alterations in specific bacterial species, have been identified. The functional significance of these changes, and their pathogenic role, remain to be elucidated.

Bacteria in the pathogenesis of inflammatory bowel disease

Twin studies have demonstrated the importance of environmental factors in the pathogenesis of inflammatory bowel disease, but progress has been relatively slow in identifying these, with the exception of smoking, which is positively associated with Crohn's disease and negatively associated with ulcerative colitis. Genetic studies have identified risk alleles which are involved in host-bacterial interactions and the mucosal barrier, and evidence is building for a likely pathogenic role for changes in the gut microbiome, with respect to both faecal and mucosa-associated microbiota. Some of these changes may be secondary to inflammation, nevertheless promising new therapeutic targets are beginning to emerge.

Fecal detection of Mycobacterium avium paratuberculosis using the IS900 DNA sequence in Crohn's disease and ulcerative colitis patients and healthy subjects

BACKGROUND AND AIM

Despite the increasing evidence of MAP/DNA isolation in Crohn's disease (CD), its potential pathogenetic role remains unclear. To further clarify the possible relationship between MAP and CD, we investigated the presence of IS900 DNA fragment in feces from Crohn's disease and ulcerative colitis (UC) patients and from healthy controls (HC).

METHODS

Stool samples were collected from 31 CD, 20 UC, and 23 HC and stored at -20°C in 200-mg aliquots. DNA was extracted. MAP presence was detected with a specific PCR amplifying a 409-bp fragment from IS900. The specificity of PCR for IS900 was confirmed sequencing three positive products. Statistical analysis was performed using the Chi-square test.

RESULTS

Twenty-one of 31 CD (68%), 13 of 20 UC (65%) and 11 of 23 HC (48%) were MAP-positive (CD vs. HC: p = ns; UC vs. HC: p = ns). With the limits of a small sample size, the IS900-positive percentage in CD and UC was higher than HC, although the difference was not statistically significant.

CONCLUSIONS

The possibility to track the MAP presence in human feces represents a new approach to the "MAP hypothesis". Detection of MAP DNA in feces is very common, reaching very high prevalence both in CD and in UC and even in HC. Our findings seem consistent with a high prevalence of MAP asymptomatic infection among the general population and so the possible involvement of MAP in CD pathogenesis could be linked to a specific immune defective response.

The human microbiome and surgical disease

OBJECTIVE

The purpose of this review article is to summarize what is currently known about microbes associated with the human body and to provide examples of how this knowledge impacts the care of surgical patients.

BACKGROUND

Pioneering research over the past decade has demonstrated that human beings live in close, constant contact with dynamic communities of microbial organisms. This new reality has wide-ranging implications for the care of surgical patients.

METHODS AND RESULTS

Recent advances in the culture-independent study of the human microbiome are reviewed. To illustrate the translational relevance of these studies to surgical disease, we discuss in detail what is known about the role of microbes in the pathogenesis of obesity, gastrointestinal malignancies, Crohn disease, and perioperative complications including surgical site infections and sepsis. The topics of mechanical bowel preparation and perioperative antibiotics are also discussed.

CONCLUSIONS

Heightened understanding of the microbiome in coming years will likely offer opportunities to refine the prevention and treatment of a wide variety of surgical conditions.

Defective innate immunity in inflammatory bowel disease: a Crohn's disease exclusivity?

PURPOSE OF REVIEW

This review summarizes the recent developments in support of the immunodeficiency model of Crohn's disease.

RECENT FINDINGS

The demonstration of impaired acute inflammation in Crohn's disease provides a novel mechanism for its pathogenesis, with diminished macrophage cytokine production and neutrophil recruitment leading to reduced bacterial clearance. The innate immune response may be further overwhelmed by other factors. The mucosal barrier in Crohn's patients is disrupted, with abnormal ultrastructure as well as antibacterial defensin deficiency. Specific bacterial agents may contribute and one promising candidate, adherent-invasive Escherichia coli, has recently been described. An interaction between Nod2 and the autophagy system has been elucidated, with direct consequences for bacterial clearance, and the most recent genome-wide association study meta-analysis has extended the number of Crohn's disease susceptibility loci to 71. The spectrum of congenital immunodeficiency disorders recognized to develop Crohn's-like inflammatory bowel disease is also expanding. Conversely, no specific immunodeficiency has so far been observed in ulcerative colitis, in which the defect appears to be failure of inflammation termination and resolution.

SUMMARY

Recent advances continue to highlight defects in innate immunity in Crohn's patients. Similar abnormalities may extend to other granulomatous disorders, but not diseases such as ulcerative colitis.

A meta-analysis of randomized controlled trials comparing antibacterial therapy with placebo in Crohn's disease

BACKGROUND

Antibacterial therapy has been investigated in several randomized, clinical trials compared with placebo for the management of Crohn's disease. Evidences for the efficacy of intervention are increasingly required.

OBJECTIVES

To conduct a meta-analysis of randomized trials to compare the effects of antibacterial therapy versus placebo in patients with Crohn's disease.

SEARCH STRATEGY

A systematic literature search of Pubmed, EMBASE, Cochrane Library (April 1966 to July 2009) was conducted using specific search terms.

SELECTION CRITERIA

Eligible studies were randomized controlled trials comparing antibacterial (antimycobacterial and broad-spectrum antibiotic) therapy with placebo.

DATA COLLECTION AND ANALYSIS

Studies were reviewed to determine the number of participants, mean follow-up, and the odds ratios (OR) for primary end point of clinical remission and clinical response were also abstracted. The meta-analysis was performed using a fixed-effects model or a randomized-effects model according to the degree of heterogeneity.

RESULTS

Eleven randomized placebo-controlled clinical trials with 668 participants (364 patients in the treatment group and, 304 patients in the placebo group) were identified. Antimycobacterial agents were used in four of the trials and broad-spectrum antibiotics were used in the other seven trials. Pooled analysis showed no significant differences in the rates of clinical remission [OR = 1.28, 95% confidence interval (CI): 0.87-1.90, P = 0.214] and clinical response (OR = 1.52, 95% CI: 0.91-2.55, P = 0.108) after receiving antibacterial treatment for 3 months or longer.

CONCLUSION

In this meta-analysis, no evidence of benefit for antibiotics in patients with Crohn's disease was found.

The commensal microbiota and enteropathogens in the pathogenesis of inflammatory bowel diseases

Intestinal inflammation arises from abnormal host-microbe interactions. The perturbations of homeostatic coexistence involve host genetic factors, barrier function, innate and adaptive immunity, as well as qualitative and quantitative changes in the composition of the microbiota. Dysbiosis toward selected micro-organisms and decreased complexity of commensal bacteria have been observed in patients with Crohn's disease and ulcerative colitis, but it is not clear whether the dysbiosis contributes to development of inflammatory bowel disease or is instead a consequence of the disease. Pathogens with virulence factors that allow them to breach the intestinal barrier and induce chronic inflammation might mediate the pathogenesis of these diseases. To identify new therapeutic approaches for inflammatory bowel disease, it is important to identify host susceptibility factors involved in the control of microbial infection, characterize potential pathogens, and eliminate them or block the expression of their virulence factors.

Current and emerging drugs for the treatment of inflammatory bowel disease

During the last decade a large number of biological agents against tumor necrosis factor-α (TNF-α), as well as many biochemical substances and molecules specifically for the medical treatment of patients with inflammatory bowel disease (IBD), have been developed. This enormous progress was a consequence of the significant advances in biotechnology along with the increased knowledge of the underlying pathophysiological mechanisms involved in the pathogenesis of IBD. However, conventional therapies remain the cornerstone of treatment for most patients. During recent years conventional and biologic IBD therapies have been optimized. Newer mesalazine formulations with a reduced pill size and only one dose per day demonstrate similar efficacy to older formulations. New corticosteroids retain the efficacy of older corticosteroids while exhibiting a higher safety profile. The role of antibiotics and probiotics has been further clarified. Significant progress in understanding thiopurine metabolism has improved the effective dose along with adjunctive therapies. Quite a large number of substances and therapies, including biologic agents other than TNF-α inhibitors, unfractionated or low-molecular-weight heparin, omega-3 polyunsaturated fatty acids, microbes and microbial products, leukocytapheresis, and other substances under investigation, could offer important benefits to our patients. In this paper we review the established and emerging therapeutic strategies in patients with Crohn's disease and ulcerative colitis.

Crohn disease: a current perspective on genetics, autophagy and immunity

Crohn disease (CD) is a chronic and debilitating inflammatory condition of the gastrointestinal tract. Prevalence in Western populations is 100-150/100,000 and somewhat higher in Ashkenazi Jews. Peak incidence is in early adult life, although any age can be affected and a majority of affected individuals progress to relapsing and chronic disease. Medical treatments rely significantly on empirical corticosteroid therapy and immunosuppression, and intestinal resectional surgery is frequently required. Thus, 80% of patients with CD come to surgery for refractory disease or complications. It is hoped that an improved understanding of pathogenic mechanisms, for example by studying the genetic basis of CD and other forms of inflammatory bowel diseases (IBD), will lead to improved therapies and possibly preventative strategies in individuals identified as being at risk.

Crohn disease: a current perspective on genetics, autophagy and immunity

Crohn disease (CD) is a chronic and debilitating inflammatory condition of the gastrointestinal tract. Prevalence in Western populations is 100-150/100,000 and somewhat higher in Ashkenazi Jews. Peak incidence is in early adult life, although any age can be affected and a majority of affected individuals progress to relapsing and chronic disease. Medical treatments rely significantly on empirical corticosteroid therapy and immunosuppression, and intestinal resectional surgery is frequently required. Thus, 80% of patients with CD come to surgery for refractory disease or complications. It is hoped that an improved understanding of pathogenic mechanisms, for example by studying the genetic basis of CD and other forms of inflammatory bowel diseases (IBD), will lead to improved therapies and possibly preventative strategies in individuals identified as being at risk.

Antibiotic therapy in inflammatory bowel disease: a systematic review and meta-analysis

The etiology of inflammatory bowel disease (IBD) is unknown but may relate to an unidentified bacterial pathogen or an immunological reaction to gut microbiota. Antibiotics have therefore been proposed as a therapy for Crohn's disease (CD) and ulcerative colitis (UC) to induce remission in active disease to prevent relapse. Current data are conflicting and we therefore conducted a systematic review of randomized controlled trials (RCTs) evaluating antibiotics in IBD. Only parallel group RCTs were considered eligible. Studies with adult patients receiving any dose of therapy for at least 7 days and up to 16 weeks for active disease, or at least 6 months of follow-up for preventing relapse in quiescent disease were analyzed. We included any antibiotics alone or in combination using predefined definitions of remission and relapse. Two reviewers independently assessed eligibility and extracted data. The primary outcome was remission or relapse using an intention-to-treat methodology. The data were summarized using relative risk (RR) and pooled using a random effects model. For active CD, there were 10 RCTs involving 1,160 patients. There was a statistically significant effect of antibiotics being superior to placebo (RR of active CD not in remission=0.85; 95% confidence interval (CI)=0.73-0.99, P=0.03). There was moderate heterogeneity between results (I(2)=48%) and a diverse number of antibiotics were tested (anti-tuberculosis therapy, macrolides, fluroquinolones, 5-nitroimidazoles, and rifaximin) either alone or in combination. Rifamycin derivatives either alone or in combination with other antibiotics appeared to have a significant effect at inducing remission in active CD. In perianal CD fistula there were three trials evaluating 123 patients using either ciprofloxacin or metronidazole. There was a statistically significant effect in reducing fistula drainage (RR=0.8; 95% CI=0.66-0.98) with no heterogeneity (I(2)=0%) and an number needed to treat 5 (95% CI=3-20). For quiescent CD, there were 3 RCTs involving 186 patients treated with different antibiotics combinations (all including antimycobacterials) vs. placebo. There was a statistically significant effect in favor of antibiotics vs. placebo (RR of relapse=0.62; 95% CI=0.46-0.84), with no heterogeneity (I(2)=0%). In active UC, there were 9 RCTs with 662 patients and there was a statistically significant benefit for antibiotics inducing remission (RR of UC not in remission=0.64; 95% CI=0.43-0.96). There was moderate heterogeneity (I(2)=69%) and antibiotics used were all different single or combination drugs. Antibiotic therapy may induce remission in active CD and UC, although the diverse number of antibiotics tested means the data are difficult to interpret. This systematic review is a mandate for further trials of antibiotic therapy in IBD.

Intestinal microbiota in inflammatory bowel disease: Friend of foe?

Inflammatory bowel disease (IBD) arises from disruption of immune tolerance to the gut commensal microbiota, leading to chronic intestinal inflammation and mucosal damage in genetically predisposed hosts. In healthy individuals the intestinal microbiota have a symbiotic relationship with the host organism and possess important and unique functions, including a metabolic function (i.e. digestion of dietary compounds and xenobiotics, fermentation of undigestible carbohydrates with production of short chain fatty acids), a mucosal barrier function (i.e. by inhibiting pathogen invasion and strengthening epithelial barrier integrity), and an immune modulatory function (i.e. mucosal immune system priming and maintenance of intestinal epithelium homeostasis). A fine balance regulates the mechanism that allows coexistence of mammals with their commensal bacteria. In IBD this mechanism of immune tolerance is impaired because of several potential causative factors. The gut microbiota composition and activity of IBD patients are abnormal, with a decreased prevalence of dominant members of the human commensal microbiota (i.e. Clostridium IXa and IV groups, Bacteroides, bifidobacteria) and a concomitant increase in detrimental bacteria (i.e. sulphate-reducing bacteria, Escherichia coli). The observed dysbiosis is concomitant with defective innate immunity and bacterial killing (i.e. reduced mucosal defensins and IgA, malfunctioning phagocytosis) and overaggressive adaptive immune response (due to ineffective regulatory T cells and antigen presenting cells), which are considered the basis of IBD pathogenesis. However, we still do not know how the interplay between these parameters causes the disease. Studies looking at gut microbial composition, epithelial integrity and mucosal immune markers in genotyped IBD populations are therefore warranted to shed light on this obscure pathogenesis.

[Gut microbiota and IBD]

Gut microbiota contains about 10(14) bacterial cells classified within 4 bacterial phyla, namely Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria. Much of the information has been generated through the application of nucleic acid-based methodologies (16S rRNA) which provide a cornerstone of microbial taxonomy. Inflammatory bowel disease (IBD) involves a dysregulated immune response to the gut microbiota in genetically predisposed hosts. Experimental animal models of colitis provide the best evidence that bacteria present in the bowel of the animals have an essential role in the pathogenesis of colitis since in most models, germ-free animals do not develop disease. Moreover, in the immunodeficient mouse model of colitis called TRUC (T-bet-/- x RAG2-/-), a colitogenic gut microbiota is selected and can be transmitted to mice with intact immunity and induce colitis. Current interest therefore focuses on the bacterial community as the source of antigens that fuel the chronic inflammation seen in IBD. Dysbiosis, an imbalance between harmful and protective bacteria, has been evoked and investigated in IBD. Thus, besides the classical pathogens, gut microbiota can drive pathogenicity via two mechanisms: an expansion of 'pro-inflammatory' species or a restriction in the protective compounds of the microbiota. Complexity of the microbiota suggests that both mechanisms may contribute to chronic gut inflammation in IBD.

Association of Mycobacterium avium subspecies paratuberculosis with Crohn Disease in pediatric patients

OBJECTIVES

The aim of the present study was to determine the prevalence of Mycobacterium avium subsp paratuberculosis (MAP) DNA in intestinal biopsies from pediatric patients with granulomatous Crohn disease (CD) or ulcerative colitis (UC), and matched control subjects without inflammatory bowel disease (IBD).

PATIENTS AND METHODS

DNA was extracted from formalin-fixed paraffin-embedded colonic and ileal biopsies from patients with CD (n = 22) or UC (n = 20), and from controls without IBD (n = 21). IS900 nested polymerase chain reaction was performed in triplicate to determine the presence of MAP-specific DNA.

RESULTS

In mucosal biopsies from terminal ileum, IS900 amplicons were detected in 1 of 19 (5.2%) control subjects, 1 of 20 (5%) patients with UC, and 7 of 20 (35%) patients with CD (P < 0.05 vs controls, odds ratio 9.6). In colonic biopsies, IS900 amplicons were detected in 0 of 19 control subjects, 1 of 19 (5.2%) patients with UC, and 5 of 19 (26.3%) patients with CD (P < 0.05 vs controls, odds ratio 14.8). In patients with CD, there was no correlation between disease activity and the presence of IS900.

CONCLUSIONS

Our technique enabled sensitive and specific detection of MAP DNA in archival endoscopic biopsy specimens. Although MAP-specific DNA can be detected in about 5% of intestinal biopsies from children with UC or controls without IBD, its presence was significantly associated with pediatric granulomatous CD, being particularly prevalent in ileal tissue. This easily defined clinical subset of patients may be useful for additional studies to determine the role of MAP in CD.

Review article: the role of non-biological drugs in refractory inflammatory bowel disease

BACKGROUND

Up to one-third of patients with inflammatory bowel disease (IBD) do not respond to, or are intolerant of conventional immunosuppressive drugs. Although biological agents are alternative treatments, they may not be suitable or available to some patients.

AIM

To review the evidence for use of nonbiological drugs in the treatment of patients with IBD refractory to corticosteroids or thiopurines.

METHODS

A literature search was performed using PubMed for English language publications with predetermined search criteria to identify relevant studies.

RESULTS

Published evidence from uncontrolled series and controlled clinical trials has been used to produce a practical approach relevant to clinical practice which incorporates the indication, optimal dose, and side effects of various therapies including tacrolimus, methotrexate, thalidomide, tioguanine, mycophenolate mofotil, leucocyte apheresis, nutritional therapy, antibiotics, probiotics, allopurinol, rectal acetarsol and ciclosporin in the treatment of patients with refractory ulcerative colitis and Crohn's disease. Approaches to optimise thiopurine efficacy are also discussed.

CONCLUSIONS

Patients with IBD refractory to corticosteroids or thiopurines may respond to alternative anti-inflammatory chemical molecules, but the evidence base for many of these alternatives is limited and further trials are needed.

Differentiation of Crohn’s disease from intestinal tuberculosis in India in 2010

Differentiating intestinal tuberculosis from Crohn’s disease (CD) is an important clinical challenge of considerable therapeutic significance. The problem is of greatest magnitude in countries where tuberculosis continues to be highly prevalent, and where the incidence of CD is increasing. The final clinical diagnosis is based on a combination of the clinical history with endoscopic studies, culture and polymerase chain reaction for Mycobacterium tuberculosis, biopsy pathology, radiological investigations and response to therapy. In a subset of patients, surgery is required and intraoperative findings with pathological study of the resected bowel provide a definitive diagnosis. Awareness of the parameters useful in distinguishing these two disorders in each of the different diagnostic modalities is crucial to accurate decision making. Newer techniques, such as capsule endoscopy, small bowel enteroscopy and immunological assays for Mycobacterium tuberculosis, have a role to play in the differentiation of intestinal tuberculosis and CD. This review presents currently available evidence regarding the usefulness and limitations of all these different modalities available for the evaluation of these two disorders.

Macrophages from IBD patients exhibit defective tumour necrosis factor-α secretion but otherwise normal or augmented pro-inflammatory responses to infection

Defects in macrophage function have been implicated in the establishment of Crohn's disease (CD). However, the response of macrophages from CD patients to live bacteria, particularly Mycobacterium avium subsp. paratuberculosis (MAP), has not been addressed. Considering MAP has long been associated to CD, our objective was to assess whether macrophages from CD patients showed impaired inflammatory response to infection by MAP comparing to M. avium subsp. avium (MA) and other live intestinal commensal bacteria. Human peripheral blood monocyte-derived macrophages were obtained from CD patients, ulcerative colitis (UC) patients and controls. Following in vitro infection with MAP, MA, Escherichia coli or Enterococcus faecalis, cytokine levels and cell surface receptor expression were evaluated at different time points. Macrophages from CD patients showed impaired TNF-α secretion in response to bacterial challenge, but augmented IL-23 secretion and preserved IL-12 secretion and CD-40 expression. In addition, CD macrophages showed low IL-10 secretion. Macrophages from IBD patients showed increased expression of TLR-2 and -4, unaffected by infection. Differences in cytokine secretion observed after bacterial challenge were not MAP-specific, as other bacteria (E. coli and MA) showed similar effects. Macrophages from UC patients showed a less compromised TNF-α synthesis in response to mycobacterial infection than CD macrophages, with increased constitutive IL-12 secretion, and preserved IL-10 secretion. The increased IL-23 levels in response to infection and decreased IL-10 production observed in macrophages from CD patients may contribute to the inflammatory exacerbation observed in those patients.

Debugging the intestinal microbiota in IBD

Besides its role in repelling enteropathogenic infections, the gastrointestinal tract is in intimate contact with commensal microbiota. Tremendous advances have been made in determining the pivotal role of the microbiota in both tissue homeostasis and metabolism, as well as in the initiation and maintenance of inflammatory lesions in inflammatory bowel diseases. A better understanding of human gut microbiota could provide innovative targets for treating and/or curing such common immunopathologies of the gastrointestinal tract.

Mucolytic bacteria with increased prevalence in IBD mucosa augment in vitro utilization of mucin by other bacteria

OBJECTIVES

Mucosa-associated bacteria are increased in inflammatory bowel disease (IBD), which suggests the possibility of an increased source of digestible endogenous mucus substrate. We hypothesized that mucolytic bacteria are increased in IBD, providing increased substrate to sustain nonmucolytic mucosa-associated bacteria.

METHODS

Mucolytic bacteria were characterized by the ability to degrade human secretory mucin (MUC2) in pure and mixed anaerobic cultures. Real-time PCR was used to enumerate mucosa-associated mucolytic bacteria in 46 IBD and 20 control patients. Bacterial mucolytic activity was tested in vitro using purified human MUC2.

RESULTS

We confirm increased total mucosa-associated bacteria 16S rRNA gene in macroscopically and histologically normal intestinal epithelium of both Crohn's disease (CD) (mean 1.9-fold) and ulcerative colitis (UC) (mean 1.3-fold). We found a disproportionate increase in some mucolytic bacteria. Mean Ruminococcus gnavus were increased >4-fold and Ruminococcus torques ∼100-fold in macroscopically and histologically normal intestinal epithelium of both CD and UC. The most abundantly detected mucolytic bacterium in controls, Akkermansia muciniphila, was reduced many fold in CD and in UC. Coculture of A. muciniphila with MUC2 as the sole carbon source led to reduction in its abundance while it augmented growth of other bacteria.

CONCLUSIONS

Mucolytic bacteria are present in healthy humans, where they are an integral part of the mucosa-associated bacterial consortium. The disproportionate increase in R. gnavus and R. torques could explain increased total mucosa-associated bacteria in IBD.

Mycobacteria in Crohn's disease: how innate immune deficiency may result in chronic inflammation

Crohn's disease (CD) is often considered to be an autoimmune condition or, alternatively, an autoinflammatory condition, based on the observation of host-directed inflammatory processes. However, the underlying basis of this deleterious inflammatory response remains elusive. Recent findings from genetic and genomic studies have altered the perspective on the pathogenesis of CD, hinting at defects in innate immune sensing of intracellular bacteria and the handling of these organisms through autophagy. These findings are consistent with emerging data from immunological studies that point to a systemic immune deficiency in CD patients. Both sets of data (genetic predisposition and immunodeficiency) are consistent with the longstanding hypothesis that mycobacteria might be involved in the etiology of CD. In this article, we discuss the convergence of these three lines of investigation and highlight important knowledge gaps required in order to address the mycobacterial hypothesis with greater clarity. In the coming years, clinical immunological investigations should focus on defining the specificity of functional immune defects with regards to microbes and their associated ligands. Should CD result from a dysfunctional host-pathogen interaction, elucidation of the microbes that can exploit such defects to induce a chronic inflammatory disease is critical for the development of subsequent diagnostic assays and clinical interventions.

Mycobacterium avium paratuberculosis and the etiology of Crohn's disease: a review of the controversy from the clinician's perspective

Mycobacterium avium paratuberculosis (MAP) is an obligate intracellular organism that has frequently been associated with Crohn's disease (CD). Because CD is a chronic inflammatory condition, many researchers have speculated that an infectious agent must be the cause of CD. MAP has often been proposed to be one such agent; however, despite considerable research, the evidence remains inconclusive. Higher levels of MAP have been found in the tissues and blood of CD patients than in controls, forming the foundation for much of the research into the role of MAP in CD and the primary argument in support of a causative role for MAP in CD. MAP is a slow-growing and fastidious organism that is difficult to grow in culture and, therefore, challenging to detect in patients. As a result, there has been variability in the results of studies attempting to detect the presence of MAP in CD patients, and considerable controversy over whether this organism has a causative role in the etiology of CD. Two main hypotheses exist with respect to the role of MAP in CD. The first is that MAP is a principal cause of CD, while the second is that MAP is more prevalent because of the immune dysfunction seen in CD but does not play a causative role. Clinicians are often faced with questions regarding the role of this organism and the need to treat it. The present article attempts to provide an overview of the controversy including the nature of the mycobacterium, the difficulty in detecting it, the use of antimycobacterial agents to treat it and the effect of immunosuppressive agents - all from a clinician's perspective. Although the role of MAP in CD remains controversial and an area of considerable research, it is currently only of academic interest because there is no clinically useful test to identify the presence of the organism, and no evidence to support the use of antibiotics to eradicate it for the treatment of CD.

Inflammatory bowel disease: Established and evolving considerations on its etiopathogenesis and therapy

Modern studies of inflammatory bowel disease (IBD) pathogenesis have been pursued for about four decades, a period of time where the pace of progress has been steadily increasing. This progress has occurred in parallel with and is largely due to developments in multiple basic scientific disciplines that range from population and social studies, genetics, microbiology, immunology, biochemistry, cellular and molecular biology, and DNA engineering. From this cumulative and constantly expanding knowledge base the fundamental pillars of IBD pathogenesis appear to have been identified and consolidated during the last couple of decades. Presently there is a general consensus among basic IBD investigators that both Crohn's disease (CD) and ulcerative colitis (UC) are the result of the combined effects of four basic components: global changes in the environment, the input of multiple genetic variations, alterations in the intestinal microbiota, and aberrations of innate and adaptive immune responses. There is also agreement on the conclusion that none of these four components can by itself trigger or maintain intestinal inflammation. A combination of various factors, and most likely of all four factors, is probably needed to bring about CD or UC in individual patients, but each patient or set of patients seems to have a different combination of alterations leading to the disease. This would imply that different causes and diverse mechanisms underlie IBD, and this could also explain why every patient displays his or her own clinical manifestations and a personalized response to therapy, and requires tailored approaches with different medications. While we are becoming increasingly aware of the importance of this individual variability, we have only a superficial notion of the reasons why this occurs, as hinted by the uniqueness of the genetic background and of the gut flora in each person. So, we are apparently facing the paradox of having to deal with the tremendous complexity of the mechanisms responsible for chronic intestinal inflammation in the setting of each patient's individuality in the response to this biological complexity. This obviously poses considerable challenges to reaching a full understanding of IBD pathogenesis, but being aware of the difficulties is the first step in finding answers to them.

High prevalence of viable Mycobacterium avium subspecies paratuberculosis in Crohn’s disease

AIM: To examine the detection rate of viable Mycobacterium avium subspecies paratuberculosis (MAP) in patients with inflammatory bowel disease [Crohn’s disease (CD) and ulcerative colitis (UC)].

METHODS: Thirty patients with CD (15 with at least one NOD2/CARD15 mutation), 29 with UC, and 10 with no inflammatory bowel disease (IBD). were tested for MAP by polymerase chain reaction (specific IS900 fragment) and blood culture.

RESULTS: MAP DNA was detected in all original blood samples and 8-wk blood cultures (CD, UC and non-IBD). Positive MAP DNA status was confirmed by dot blot assays. All 69 cultures were negative by acid-fast Ziehl-Neelsen staining. Viable MAP, in spheroplast form, was isolated from the 18-mo blood cultures of all 30 CD patients, one UC patient, and none of the non-IBD controls. No association was found between positive MAP cultures and use of immunosuppressive drugs or CD-associated single nucleotide polymorphisms.

CONCLUSION: MAP is widely present in our area and MAP DNA can be recovered from the blood of CD, UC and non-IBD patients. However, MAP spheroplasts were only found in CD patients.

The role of bacteria in the pathogenesis of inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) have features that suggest bacterial involvement, and all genetic models of inflammatory bowel disease (IBD) require the presence of commensal bacteria. CD is associated with innate immune response genes such as NOD2/CARD15 and the autophagy genes ATG16L1 and IRGM. However, IBD responds to immunosuppression, suggesting that any bacteria involved are not acting as conventional pathogens. Molecular techniques are rapidly advancing our knowledge of the gut microbiota. In CD there is reduced diversity, and notably a reduction in the probiotic Faecalibacterium prausnitzii, the presence of which in the terminal ileum is associated with a reduced risk of recurrence following surgery. There is also a consistent increase in mucosa-associated Escherichia coli with an "adherent and invasive" phenotype, which allows them to replicate inside macrophages and induce granulomas. Speculation that CD could be caused by the Mycobacterium avium subspecies paratuberculosis (MAP) continues. The response to antitumor necrosis factor treatments suggests that, if relevant at all, MAP is not acting as a conventional pathogen. However, there is increased colonization by MAP in CD, and there is evidence that it could have an indirect effect mediated by the suppression of macrophage function. UC relapse is frequently associated with infection by pathogens, but there is less evidence for involvement of a specific bacterial species. Poor barrier integrity followed by an inflammatory reaction to bacterial components, with chronicity maintained by an autoimmune process, seems a plausible pathogenic model. Bacterial theories of pathogenesis are now becoming testable by targeted therapeutic interventions.

The intestinal microbiota in inflammatory bowel diseases: time to connect with the host

PURPOSE OF REVIEW

The aim of this review is to report recent findings regarding the role of the gut microbiota in inflammatory bowel disease pathogenesis.

RECENT FINDINGS

After a description of the current knowledge on inflammatory bowel diseases-associated dysbiosis, we will focus on the recent functional studies that analyzed the cross relationship between the gut microbiota and the host.

SUMMARY

Recently published studies have provided an insight into the altered dialog between the intestinal microbiota and the host leading to gut inflammation. Further investigation will allow identifying new therapeutic targets either in the microbiota or the host.

Suspected intestinal tuberculosis might be Crohn's disease

In this case report we provide evidence that supports a link between mycobacteria and Crohn's disease. The patient in question, KG, presented on three separate occasions over a ten years period with features suggestive of intestinal tuberculosis. He was treated successfully on each occasion with antimycobacterial drugs. When he presented a fourth time with the same symptoms, he was diagnosed with Crohn's disease based on findings from endoscopy, histology and CT. Subsequently he was treated with a course of steroids and made a full recovery. This case adds weight to the theory that mycobateria has an aetiological role in Crohn's disease.

Absence of Mycobacterium avium ss paratuberculosis-specific IS900 sequence in intestinal biopsy tissues of Indian patients with Crohn's disease

BACKGROUND AND OBJECTIVE

The role of Mycobacterium avium ss paratuberculosis (MAP) in the etiopathology of Crohn's disease (CD) remains controversial, because of conflicting reports demonstrating the presence of MAP-specific insertion sequence from intestinal biopsy tissues of patients clinically diagnosed for the disease. The present study was carried out to investigate the presence of MAP DNA in the intestinal tissues of CD patients to ascertain the relevance of MAP in Indian patients with CD.

METHODS

Patients diagnosed as CD at our institute were recruited. Healthy individuals without inflammatory bowel disease served as controls. Mucosal biopsy specimens were collected from ileum and colon in duplicates and subjected to histopathological examination and polymerase chain reaction (PCR) amplification. Total DNA (81 CD patients, 85 healthy individuals) and total RNA (12 CD patients, 12 healthy individuals) isolated from tissue specimens was used for amplification of MAP-specific IS900 by nested PCR.

RESULTS

MAP-specific IS900 DNA and RNA could not be detected by nested PCR in the intestinal tissues of any patient with CD.

CONCLUSION

Our results do not support the etiological role of MAP in the pathogenesis of CD in Indian patients.

Common polymorphisms in the NOD2 gene region are associated with leprosy and its reactive states

BACKGROUND

Because of its wide spectrum of clinical manifestations and its well-defined immunological complications, leprosy is a useful disease for studying genetic regulation of the host response to infection. We hypothesized that polymorphisms in the nucleotide-binding oligomerization domain containing 2 (NOD2) gene, for a cytosolic receptor known to detect mycobacteria, are associated with susceptibility to leprosy and its clinical outcomes.

METHODS

We used a case-control study design with 933 patients in Nepal. Our study included 240 patients with type 1 (reversal) reactions and 124 patients with type 2 (erythema nodosum leprosum) reactions. We compared the frequencies of 32 common polymorphisms in the NOD2 gene region between patients with the different clinical types of leprosy as well as between the patients and 101 control participants without leprosy.

RESULTS

Four polymorphisms were associated with susceptibility to leprosy when comparing allele frequencies, and 8 were associated when comparing genotype frequencies with a dominant model. Five polymorphisms were associated with protection from reversal reaction in an allelic analysis, and 7 were associated with reversal reaction with a dominant model. Four polymorphisms were associated with increased susceptibility to erythema nodosum leprosum in an allelic analysis, whereas 7 of 32 polymorphisms were associated with a dominant model.

CONCLUSION

These data suggest that NOD2 genetic variants are associated with susceptibility to leprosy and the development of leprosy reactive states.

Crohn's disease: an immune deficiency state

Crohn's disease is a chronic inflammatory disorder primarily affecting the gastrointestinal tract. Its clinical manifestations arise from a substantial infiltration of the intestinal mucosa by activated leukocytes and the downstream consequences of chronic inflammation. The underlying cause driving this immunological reaction remains poorly understood. A number of hypotheses have been proposed, most of which postulate a primary over-activation of the immune response, based on the pathological appearances of active Crohn's lesions. Interestingly, none of these theories have been mechanistically proven. It is possible that the immunological events responsible for disease initiation are quite different from those contributing to its persistence and propagation. A substantial body of data has emerged in recent years to suggest that the primary defect in Crohn's disease is actually one of relative immunodeficiency. This review considers the evidence for such a phenomenon in contrast to alternative prevailing hypotheses and attempts to address some of the potential paradoxes that it generates.

What is the optimal therapy for Crohn's disease: step-up or top-down?

Crohn's disease (CD) is an idiopathic chronic inflammatory disorder of the digestive tract, which is incurable. Present therapeutic guidelines follow a sequential step-up approach that focuses on treating acute disease or 'inducing clinical remission' and subsequently aims to 'maintain clinical response'. In view of the chronic relapsing-remitting disabling disease course, new treatment approaches have been sought with the ultimate end point of disease course modification and mucosal healing. A recent preliminary study from D'Haens et al. has provided evidence suggesting that reversing the treatment paradigm from a 'step-up' to a 'top-down' approach may positively alter the natural course of this illness. Their findings indicate that early use of biologic therapy, in combination with immunomodulators, resulted in remission occuring more rapidly than the conventional 'step-up' treatment, with a longer time period to relapse, a decreased need for treatment with corticosteroids, a faster reduction in clinical symptoms, rapid decline in biochemical inflammatory markers (C-reactive protein) and improved endoscopic mucosal healing. These results, supported by previous studies on infliximab use, may hold a promising outcome of fewer stricturing complications, hospitalizations and surgeries for patients with CD. However, we need to better define the timing and candidates for the 'top-down' approach as we are still uncertain about the safety data and the long-term benefits if biologic agents are given as routine maintenance treatment, since most of the trials in CD have been short term, and approximately 30% of patients might have been overtreated. Future clinical trials will be crucial in answering these questions.

Is Mycobacterium avium subsp. paratuberculosis, the cause of Johne's disease in animals, a good candidate for Crohn's disease in man?

Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's disease or paratuberculosis, a gastro intestinal inflammatory condition in ruminants and other animals, which is similar to Crohn's disease (CD) that occurs in man. The role of MAP in the causation of CD has been under intense investigation in the last few decades. This review summarizes the status of MAP in animals and the food chain and its association with CD in man.

Optimizing conventional therapies for inflammatory bowel disease

Conventional therapies remain the mainstay of treatment for most patients with inflammatory bowel disease (IBD), with only a minority of patients requiring biologic therapies. Recently, attention has focused on optimizing dosing strategies for biologic agents; however, of equal importance are recent advances in the optimization of conventional IBD therapies. Newer aminosalicylate formulations demonstrate similar efficacy with a reduced pill burden and less frequent dosing, while new corticosteroid preparations may retain efficacy with a significantly improved safety profile. The limited indications for antibiotics and probiotics have been further refined by recent data, although uncertainties remain. Advances in the understanding of thiopurine metabolism continue to improve dose optimization and the potential for deliberate therapeutic manipulation with adjunctive therapies. An improved knowledge of intracellular methotrexate metabolism may translate to similar opportunities in the future. This article discusses recent advances relevant to clinical practice today.

Systematic review of the evidence base for the medical treatment of paediatric inflammatory bowel disease

OBJECTIVE

To systematically review the evidence base for the medical (pharmaceutical and nutritional) treatment of paediatric inflammatory bowel disease.

METHODS

Key clinical questions were formulated regarding different treatment modalities used in the treatment of paediatric (not adult-onset) IBD, in particular the induction and maintenance of remission in Crohn disease and ulcerative colitis. Electronic searches were performed from January 1966 to December 2006, using the electronic search strategy of the Cochrane IBD group. Details of papers were entered on a dedicated database, reviewed in abstract form, and disseminated in full for appraisal. Clinical guidelines were appraised using the AGREE instrument and all other relevant papers were appraised using Scottish Intercollegiate Guidelines Network methodology, with evidence levels given to all papers.

RESULTS

A total of 6285 papers were identified, of which 1255 involved children; these were entered on the database. After critical appraisal, only 103 publications met our criteria as evidence on medical treatment of paediatric IBD. We identified 3 clinical guidelines, 1 systematic review, and 16 randomised controlled trials; all were of variable quality, with none getting the highest methodological scores.

CONCLUSIONS

This is the first comprehensive review of the evidence base for the treatment of paediatric IBD, highlighting the paucity of trials of high methodological quality. As a result, the development of clinical guidelines for managing children and young people with IBD must be consensus based, informed by the best-available evidence from the paediatric literature and high-quality data from the adult IBD literature, together with the clinical expertise and multidisciplinary experience of paediatric IBD experts.

Mycobacterium avium subspecies paratuberculosis in children with early-onset Crohn's disease

BACKGROUND

Mycobacterium avium subspecies paratuberculosis (MAP) is the most enduring infectious candidate that may be associated with inflammatory bowel disease (IBD). It is possible that the inconsistencies in the prevalence studies of MAP in adults reflect clinical differences in adult patients studied, including duration of disease and treatment regimens, and also in lack of specificity of some of the assays used. The aim was to determine the presence of MAP in children with symptoms of Crohn's disease (CD) and ulcerative colitis (UC), using gut biopsy tissue and peripheral blood mononuclear cells (PBMC) collected at initial endoscopic examination prior to clinical treatment.

METHODS

Mucosal biopsies and/or PBMC specimens were collected from a total of 142 children, comprising 62 with CD, 26 with UC, and 54 with non-IBD. MAP-specific IS900 polymerase chain reaction (PCR) analysis was performed on all biopsies and PBMC specimens. Conventional MAP culture technique was performed on a subset of 10 CD, 2 UC, and 4 non-IBD patients to isolate MAP.

RESULTS

MAP was identified by IS900 PCR significantly more often in mucosal biopsies from CD 39% (22/56) than from non-IBD 15% (6/39) patients (P < 0.05), and in PBMC from CD 16% (8/50) than from non-IBD 0% (0/31) patients (P < 0.05). Viable MAP were cultured from mucosal biopsies from 4/10 CD, 0/2 UC, and 0/4 non-IBD patients, but were not cultured from PBMC specimens.

CONCLUSIONS

This unique study on the occurrence of MAP in gut tissue and blood from pediatric IBD patients suggests the possible involvement of MAP in the early stages of development of CD in children.

Crohn disease and mycobacterial infection in children: an intriguing relationship

The relation between Crohn disease (CD) and mycobacterial infection is complex and intriguing. The 2 conditions share common immunopathogenic features, and the hypothesis that Mycobacterium avium subspecies paratuberculosis may cause CD is still under debate. Moreover, differential diagnosis between CD and intestinal tuberculosis (TB) may be challenging, especially in the growing proportion of children immigrating from countries with a high prevalence of TB. Thus, in Western countries, paediatricians who are involved in the diagnosis and management of children with CD are expected to face intestinal TB more frequently than in the past and should always consider the differential diagnosis between these 2 conditions. In addition, the use of biological agents in the treatment of CD, which may reactivate latent TB, requires the development of targeted diagnostic algorithms. Children with CD who are candidates for treatment with antitumour necrosis factor-alpha agents should be screened for latent or active TB and closely followed over time, also considering possible failure of antitubercular prophylaxis and the frequent uncharacteristic presentation of TB in children receiving antitumour necrosis factor-alpha agents. In the present review, the most recent literature findings on these topics are reported, focusing particularly on the paediatric age group.

Overview of inflammatory bowel disease in Australia in the last 50 years

Inflammatory diseases of the intestine, including Crohn's disease, ulcerative colitis, and celiac disease are now very common in Australia and remain major challenges for clinicians. Australian (and New Zealand) clinicians and scientists have made considerable contributions to our current understanding of these diseases over the last 50 years, including pathogenesis (such as the 'butyrate hypothesis', 'endoplasmic reticulum (ER) stress', and the identification of the peptide sequences that incite celiac disease), true population epidemiology (albeit in New Zealand), precise clinical observation, new investigative tools, innovative new potential therapies, influential clinical drug trials (such as triple antibiotics for Crohn's disease), and a dietary approach with efficacy for functional gut symptoms (the low FODMAP diet). Underpinning the success has been clinical excellence and adaptation of clinicians to the changing landscape of disease severity and therapeutic options. The future is indeed bright if such trends continue.

Effects of interactions of antibacterial drugs with each other and with 6-mercaptopurine on in vitro growth of Mycobacterium avium subspecies paratuberculosis

OBJECTIVES

Mycobacterium avium subspecies paratuberculosis (MAP) has been targeted for treatment with clarithromycin and rifamycin derivatives in numerous cases of Crohn's disease (CD). 6-Mercaptopurine and its pro-drug azathioprine are widely used as immunomodulators in the treatment of CD and have recently been shown to have anti-MAP activity in vitro. The objectives of the study were to evaluate the in vitro effects on MAP of (i) 6-mercaptopurine when combined with each of eight conventional antibacterial agents with in vitro anti-MAP activity and (ii) antibacterial combinations consisting of two drugs (clarithromycin combined with amikacin, rifampicin, ciprofloxacin or ethambutol) and three drugs (clarithromycin, rifabutin and clofazimine).

METHODS

The drug interaction effects on nine human isolates of MAP were determined by the chequerboard method adapted for the BACTECMGIT960 culture system and by calculation of the fractional inhibitory concentration index (FICI) for drug combinations.

RESULTS

Synergism (FICI < or = 0.5) was observed between 6-mercaptopurine and azithromycin (seven isolates), clarithromycin, rifampicin, rifabutin (four isolates each) and ethambutol (two isolates). 6-Mercaptopurine was not antagonistic with any of the antibacterial agents tested. Among the combinations of two and three antibacterials tested, the clarithromycin/rifampicin combination was synergistic against four isolates, while all other combinations showed no interaction.

CONCLUSIONS

This in vitro study suggests that 6-mercaptopurine may be synergistic with macrolides and rifamycin derivatives against MAP. The activity of clarithromycin against MAP seems to be enhanced by rifampicin.

[Inflammatory bowel disease: genetic or environmental diseases?]

Pathophysiology of inflammatory bowel diseases depends on the interaction between genetic susceptibility and environmental factors leading to a deregulated immune intestinal response resulting in bowel lesions. Epidemiologic variations of inflammatory bowel diseases with time (incidence, prevalence) and space suggest a role for risk environmental factors, but so far only smoking habits and appendectomy have been identified as influencing the risk of occurrence and the course of the diseases. Studies of monozygotic and dizygotic twins and the existence of familial aggregation are strong evidence for an important, but not exclusive, role for genetic susceptibility. Since the discovery of NOD2/CARD15 mutations, numerous genes have been associated with inflammatory bowel diseases, some of them involved in the regulation of innate immunity and cellular clearance of infectious agents (autophagy). Thus, new hypothesis include a key role of mucosal human microbiota which could be partly influenced by environmental factors generated by modern life. The improvement of life hygiene, the change of food composition and habits, the industrial pollution in developed countries, may influence, directly or by the way of modifying intestinal human microbiota, inflammatory bowel diseases risk occurrence.