[Probiotics in gastrointestinal pathology]

There are a variety of conditions in which the use of pro-biotics has proven effective:diarrhoea with its various causes, inflammatory bowel diseases, irritable bowel disease, colon cancer chemoprevention and hepato-portal encefalopathy. The pro-biotics have shown to be a promising therapeutical alternative for the future due to their lack of side effects and convenient mode of administration. Further, the potential of other pro-biotics is awaiting validation by clinical trials.

Microbial factors in inflammatory bowel disease

An unsolved puzzle in IBD research is whether germs, genes, or a combination of the two with excessive immune responses to gut-associated bacteria explains the pathogenesis of UC and CD. Whatever the answer, there is little doubt that microbial factors are involved intimately in IBD pathogenesis. Although a long search has failed to confirm a direct pathogenic role for a specific infectious agent, compelling evidence suggests that commensal enteric bacteria and their products provide a local environmental trigger that initiates and perpetuates IBD, reactivates quiescent disease, results in the frequent septic complications of CD, and contributes to the development of several extraintesinal manifestations. The most compelling evidence for involvement of the enteric flora in the pathogenesis of IBD has been generated from studies of animal models, which collectively support the view that IBD is due to genetically determined dysregulation of the mucosal immune response to luminal antigens derived from the normal bacterial flora. Although removing or dampening the dominant antigenic stimuli with antibiotics or probiotics is conceptually superior to the current array of immunosuppressive and anti-inflammatory agents that nonspecifically block the inflammatory cascade, more definitive, rigorously designed, controlled trials of treatments directed at the microflora are needed. Future research investigating mechanisms of tolerance to luminal bacteria and an understanding of how probiotics can manipulate the intestinal flora beneficially will bring clinicians closer to identifying potential therapeutic targets and unraveling the bacterial connection to IBD pathogenesis.

The bacterial flora in inflammatory bowel disease: current insights in pathogenesis and the influence of antibiotics and probiotics

The pathogenesis of inflammatory bowel disease (IBD) remains unknown, although in recent years more data have become available. The contribution of genetic and environmental factors is evident, and the luminal bacterial flora plays a major role in the initiation and perpetuation of chronic IBD. Animal models of IBD have shown that colitis does not occur in a germ-free environment. In human IBD, inflammation is present in parts of the gut containing the highest bacterial concentrations. Moreover, the terminal ileum, caecum and rectum are areas of relative stasis, providing prolonged mucosal contact with luminal contents. Enhanced mucosal permeability may play a pivotal role in maintaining a chronic inflammatory state, due to a genetic predisposition or as a result of direct contact with bacteria or their products. A detective epithelial barrier may cause a loss of tolerance to the normal enteric flora. Furthermore, an increased mucosal absorption of viable bacteria and bacterial products is found in IBD. Serum and secreted antibodies are increased and mucosal T-lymphocytes that recognize luminal bacteria are present. However, there is evidence that the immune system reacts over aggressively towards the normal luminal flora rather than the flora being altered in IBD. Several approaches have been used in attempts to discover a specific microbial agent in the cause of IBD. These include demonstration of the presence of organisms or specific antigens in affected tissues, culture of microbes firm the affected tissues, demonstration of serological responses to several agents, and localization and detection of individual pathogen-specific nucleic acid sequences in affected tissue by in situ hybridization and polymerase chain reaction. So far, no specific micro-organism has been directly associated with the pathogenesis of IBD. Analysis of the luminal enteric flora, however, has revealed differences in the composition of this flora compared to healthy controls. In Crohn disease, concentrations of Bacteroides, Eubacteria and Peptostreptococcus are increased, whereas Bifidobacteria numbers are significantly reduced. Furthermore, in ulcerative colitis, concentrations of facultative anaerobic bacteria are increased. The arrival of new molecular techniques qualifying and quantifying the complex intestinal flora has induced a revival of interest in this microflora. Therapeutic approaches geared towards changing the environment at the mucosal border have been attempted by the use of elemental diets, total parenteral nutrition, surgical diversion of the faecal stream and antibiotics. Over the past few years, the use of probiotics in IBD and other intestinal disorders has gained attention. Strengthened by promising experimental data and commercial interests, research in this field is rapidly expanding. Manipulation of the colonic bacteria with antibiotic drugs and probiotic agents may prove to be more effective and better tolerated than immunosuppressants in the future.

Helicobacter bilis infection accelerates and H. hepaticus infection delays the development of colitis in multiple drug resistance-deficient (mdr1a-/-) mice

mdr1a-deficient mice lack P-glycoprotein and spontaneously develop colitis with age. Helicobacter spp. are gram-negative organisms that have been associated with colitis in certain mouse strains, but Helicobacter spp. have been excluded as contributing to the spontaneous colitis that develops in mdr1a-/- mice. We wished to determine whether infection with either H. bilis or H. hepaticus would accelerate the development of inflammatory bowel disease (IBD) in mdr1a-/- mice. We found that H. bilis infection induced diarrhea, weight loss, and IBD in mdr1a-/- mice within 6 to 17 weeks post-inoculation and before the expected onset of spontaneous IBD. Histopathology of H. bilis-induced IBD included crypt hyperplasia, inflammatory cell infiltrates, crypt abscesses, and obliteration of normal gut architecture. Reverse transcription-polymerase chain reaction and Taqman analysis from colonic tissue showed increased transcripts for interferon-gamma and interleukin-10 from H. bilis-infected colitic mdr1a-/- mice. Additionally, mesenteric lymph nodes had increased cellularity with expansion of CD4+ and CD8+ T cells and B cells and increased proliferation to soluble H. bilis antigens with elaboration of interferon-gamma, tumor necrosis factor-alpha and interleukin-10. In contrast, H. hepaticus infection of mdr1a-/- mice did not accelerate disease but rather delayed the onset of spontaneous colitis which was milder in severity. mdr1a-/- mice infected with Helicobacter spp. may provide a useful tool to explore the pathogenesis of microbial-induced IBD in a model with a presumed epithelial cell "barrier" defect.

Mucosal flora in inflammatory bowel disease

BACKGROUND & AIMS

Microorganisms that directly interact with the intestinal mucosa are obscured by fecal flora and poorly characterized.

METHODS

We investigated the mucosal flora of washed colonoscopic biopsies of 305 patients with bowel inflammation and 40 controls. The microbial cultures were validated by quantitative polymerase chain reaction with subsequent cloning and sequencing, fluorescence in-situ hybridization, and electron microscopy.

RESULTS

We found high concentrations of mucosal bacteria in patients with bowel inflammation, but not in controls. The concentrations of mucosal bacteria increased progressively with the severity of disease, both in inflamed and non-inflamed colon. In patients with >10,000 cfu/microL, a thick bacterial band was attached to the intact mucosa without signs of translocation. Patients with inflammatory bowel disease (IBD) and concentrations of mucosal bacteria >50,000 cfu/microL had characteristic inclusions of multiple polymorphic bacteria within solitary enterocytes located next to the lamina propria, without or having no contact with the fecal stream. The identified bacteria were of fecal origin.

CONCLUSIONS

Our findings suggest that the changes in the mucosal flora in IBD are not secondary to inflammation, but a result of a specific host response. We hypothesize that the healthy mucosa is capable of holding back fecal bacteria and that this function is profoundly disturbed in patients with IBD.

Current dilemmas in the management of inflammatory bowel disease

Considerable advances have been made in the treatment of inflammatory bowel disease (IBD) mainly in that of Crohn's disease, but many questions still remain. We need to develop treatments that modify the disease. The use of immunomodulation using cytokines and anti-cytokines is an important step to achieve this goal. The standard is now the chimeric monoclonal antibody against tumour necrosis factor (TNF) in Crohn's disease. These treatments, however, are associated with problems of immunogenicity and autoimmunity. Moreover a proportion of patients do not respond to treatment and we do not have measurements that predict response. The optimal use and the combined treatment with immunosuppression are under investigation. The safety of this treatment in the long-term is also not established. These costly drugs are not suitable for the management of mild to moderate Crohn's disease and ulcerative colitis (UC). If it turns out that the antigenic drive of the inappropriate immune reaction is in the lumen of the gut changing the gut flora by using probiotics may be the way to go.

[Enterotoxigenic Bacteroides fragilis as a factor in diarrhea]

The etiology of almost half of the diarrheal diseases has not been cleared yet, in spite of modern diagnostic methods. Bacteroides fragilis strains which secrete an enterotoxin are termed as enterotoxigenic B.fragilis (ETBF). These strains are associated with diarrheal diseases in children above 1 year of age and in adults. B. fragilis toxin (BFT) stimulates intestinal secretion and in-vitro cytotoxic response in HT29/C1 cells. Recent studies suggest that BFT is related to inflammatory bowel disease and colon cancer by triggering nuclear activation with potential oncogene expression. In this review, the molecular pathogenesis, epidemiology and laboratory diagnosis of ETBF have been reviewed to focus on ETBF as a diarrheal agent.

Bacteroides ovatus as the predominant commensal intestinal microbe causing a systemic antibody response in inflammatory bowel disease

To clarify what bacterial species of commensal intestinal microbes are recognized as the antigens that induce a serum antibody response in patients with inflammatory bowel disease (IBD), 72 subjects consisting of 12 Crohn's disease patients, 30 ulcerative colitis patients, and 30 healthy volunteers were examined for their titers of serum antibody to these intestinal bacteria. In IBD patients, as a result, significant elevations of both the immunoglobulin G (IgG) and IgA titers to Bacteroides ovatus were found. Immunoblotting showed that a definite 19.5-kDa band of B. ovatus was bound to the serum antibody raised in IBD patients. It was thus concluded that B. ovatus causes serum antibody responses in IBD patients, and a 19.5-kDa molecule of this bacterium appears to be the responsible antigen, although the role of this event in pathogenesis remains unclear.

Inflammatory bowel disease: is the intestine a Trojan horse?

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory condition of the intestines that is clinically heterogenous. The cause(s) of IBD are currently unknown but the mechanisms of injury are immunological. Increasingly there is an emphasis on the study of the complex interactions at the interface of self and non-self--the gastrointestinal epithelial surface--in relationship to the pathogenesis of disease. There is mounting evidence that a lack of tolerance to the normal commensal flora of the intestine may underlie the disease pathogenesis. Several genetic loci that are markers of disease susceptibility have been identified. These loci map to areas of the genome that are concerned with antigen presentation or cytokine secretion and suggest a genetic heterogeneity that underlies the clinical differences. Overall a picture is emerging of defects in epithelial barrier function and, or immunoregulation leading to immune responses that are triggered or exaggerated by the antigenic components of the normal flora.

New food components and gastrointestinal health

Apart from its main functions of digestion, absorption and faecal processing, the human gastrointestinal tract has a complex pattern of muscular activity regulated by a largely autonomous nervous system, and its various organs contain large concentrations of immune and endocrine tissues. Any failure of these closely-integrated systems can lead to diseases ranging from the mildly irritating to the life threatening. Food contains a huge variety of chemical species, many of which are biologically active, and the distal regions of the gut are colonised by a rich and metabolically-active commensal flora that depend on nutrients derived ultimately from the host's dietary residues. The present paper explores the evidence for significant effects of food ingredients on functional bowel disorders, intestinal infections, and aspects of epithelial cell physiology involved in the development of colo-rectal neoplasia. Various strategies, including the manipulation of the colo-rectal microflora with pre- and probiotics, and the development of new products and plant varieties containing biologically-active constituents, have the potential to underpin the development of novel functional food products. However, these products will need to be based on proven biological principles, and fully tested for efficacy and safety. The rapidly-developing fields of functional genomics and cell biology will open up new experimental strategies to explore these possibilities, and emerging processing technologies seem likely to provide novel methods for their exploitation.

Microbiological and immunological strategies for treatment of inflammatory bowel disease

Chronic inflammatory bowel diseases such as Crohn's disease or ulcerative colitis, affect around 1 in every 1000 individuals in western countries. They probably result from an inappropriate reaction towards the commensal microflora and are currently treated with anti-inflammatory drugs or surgery. Novel strategies aim at blocking lymphocyte recruitment and activation, improved targeting of therapeutics and modification of gut microflora.

Immunology of inflammatory diseases of the bowel

During the past century, research on animal diseases has focused on the characterization of specific etiologies and disease control strategies. Many diseases affecting domestic animals have been successfully controlled using various methods, including vaccination, management, vector control, or antimicrobial agents. A number of microorganisms have proven resistant to these efforts. Control of these organisms requires the development of new strategies. As practitioners and researchers, we need to consider approaches that encompass the entire realm of disease expression from molecular to immune responses and interactions with other functional systems (e.g., endocrine, neurologic, and vascular systems). We need a basic understanding of effective immune responses enabling the tailoring of vaccines to produce the desired response. This tailoring of host responses is augmented by the use of vaccines that use host growth factors, cytokines, or costimulatory molecules to bias the ensuing response. Intestinal microbial flora of food-producing animals can be managed to optimize health and minimize colonization by pathogenic organisms, especially zoonotic agents. New systems for the delivery of cytokines and other factors that favor optimal intestinal health and homeostasis need to be researched and evaluated. With time, it is likely that our clients and the consumers will be less tolerant of antibiotic usage. They will be more aware of the zoonotic potential of many microbes that colonize food animals. Food safety issues will be a continuing concern, as will the protection of our water supply from contamination from feedlots and pasture runoff. We are in the dawn of a new century, and, it is hoped, a new era of discovery of enteric disease pathogenesis and control.

High prevalence of Mycoplasma pneumoniae in intestinal mucosal biopsies from patients with inflammatory bowel disease and controls

Intestinal microflora are believed to play an important role in the pathogenesis of inflammatory bowel disease (IBD). Mycoplasma have been suggested previously as organisms of ubiquitous distribution with the potential to cause inflammatory diseases, including IBD in susceptible individuals. The aim of this study was to determine the frequency of the presence of M. pneumoniae DNA in intestinal biopsies from patients with IBD and non-IBD controls using a microplate polymerase chain reaction-hybridization assay (PCR-ELISA). A total of 260 endoscopic biopsies (49 from 19 patients with Crohn's disease, 76 from 27 patients with ulcerative colitis, and 135 from 43 non-IBD controls) were used in this study. Overall, M. pneumoniae-specific DNA was detected in 100 endoscopic biopsy samples (38.5%). Among them, the detection rate of M. pneumoniae DNA was significantly higher in biopsies from patients with CD (59.2%) than in those from patients with UC (26.3%) or non-IBD controls (37.7%) (chi2 = 13.65, P < or = 0.001). The high prevalence of M. pneumoniae in both IBD patients and controls suggest this organism is ubiquitous and may persist in the intestinal mucosa. Epidemiological studies in IBD suggest acquisition of some agents early in life probably during epidemics in temperate latitudes. M. pneumoniae could be one of the ubiquitous agents implicated in the pathogenesis of IBD.

New Helicobacter species in humans

During the last decade several new Helicobacter species have been isolated from human gastric mucosa, fecal samples, liver, and gallbladder. Gastric corkscrew-shaped Helicobacter species: H. heilmannii is usually seen in the gastric foveolae in 0.2-0.6% of histological sections from the gastric mucosa of patients with dyspepsia in Western Europe, but it has only been cultured once. It is genetically and morphologically closely related to H. bizzozeronii and H. salmonis which are common in dogs and cats. It causes constantly active chronic gastritis and is regularly associated with peptic ulcer. Intestinal Helicobacter species: H. cinaedi, H. fennelliae, H. pullorum, H. westmeadii, H. canadensis, and 'H. rappini' have been isolated from patients with enteritis and proctitis. H. fennelliae, H. cinaedi, H. westmeadii, and 'H. rappini' have been isolated also from patients with septicemia. Studies indicate that H. cinaedi is transmitted from hamsters and that H. pullorum is common in chickens. 'H. rappini' has been isolated from sheep, dogs, and mice, whereas no animal reservoir has been found for H. fennelliae. Except for the cases of septicemia, none of these Helicobacter species have yet been proven to cause human disease, but they are suspected to play a role in inflammatory bowel diseases. Hepatobiliary Helicobacter species include several Helicobacter species isolated from bile and liver of animals, but only H. bilis has been isolated from the human gallbladder and H. pylori from the human liver. H. bilis has been isolated from dogs, cats, mice, and rats. Nonpylori Helicobacter species are usually difficult to culture and may be more frequently causes of human disease than realized today.

Failure of single-toxin assays to detect clostridium difficile infection in pediatric inflammatory bowel disease

OBJECTIVES

The aims of this retrospective study were 1) to determine the ability of single-toxin assays for Clostridium difficile to detect infection among pediatric patients with inflammatory bowel disease (IBD) and 2) to determine the toxin assays routinely used by pediatric tertiary care hospitals in the United States.

METHODS

Stool specimens from patients with IBD (submitted from January, 1996, to August, 1999) were evaluated for the presence of C. difficile toxin A and toxin B. Toxin profile (toxin A alone, toxin B alone, toxin A and B together) was compared in positive specimens. A phone interview was conducted with representatives from laboratories in 22 pediatric hospitals to investigate which toxin assays were routinely used.

RESULTS

A total of 697 specimens were submitted from 284 IBD patients. In all, 81 IBD patients (28.5%) had at least one documented infection. Toxin A assay failed to identify 41.5% of C. difficile infections. Toxin B assay failed to detect 34.9% of C. difficile infections. Toxin profile changed in 55% of patients with multiple infections. Of the hospitals surveyed, 59% did not test for both toxins.

CONCLUSIONS

Single-toxin assays for C. difficile fail to detect a significant percentage of infections. The toxins identified during one infection are not predictive of the toxins identified in subsequent infections. Despite this, many pediatric hospitals do not routinely use both toxin assays to diagnose C. difficile infection. When infection is suspected, assays for C. difficile toxin A and toxin B should be requested.

Helicobacter-induced inflammatory bowel disease in IL-10- and T cell-deficient mice

Inflammatory bowel disease (IBD) is thought to result from a dysregulated mucosal immune response to luminal microbial antigens, with T lymphocytes mediating the colonic pathology. Infection with Helicobacter spp has been reported to cause IBD in immunodeficient mice, some of which lack T lymphocytes. To further understand the role of T cells and microbial antigens in triggering IBD, we infected interleukin (IL)-10(-/-), recombinase-activating gene (Rag)1(-/-), T-cell receptor (TCR)-alpha(-/-), TCR-beta(-/-), and wild-type mice with Helicobacter hepaticus or Helicobacter bilis and compared the histopathological IBD phenotype. IL-10(-/-) mice developed severe diffuse IBD with either H. bilis or H. hepaticus, whereas Rag1(-/-), TCR-alpha(-/-), TCR-beta(-/-), and wild-type mice showed different susceptibilities to Helicobacter spp infection. Proinflammatory cytokine mRNA expression was increased in the colons of Helicobacter-infected IL-10(-/-) and TCR-alpha(-/-) mice with IBD. These results confirm and extend the role of Helicobacter as a useful tool for investigating microbial-induced IBD and show the importance, but not strict dependence, of T cells in the development of bacterial-induced IBD.

Cholangiohepatitis and inflammatory bowel disease induced by a novel urease-negative Helicobacter species in A/J and Tac:ICR:HascidfRF mice

Helicobacter bilis and H. hepaticus, both urease-positive intestinal helicobacters of mice, have been shown experimentally to induce proliferative typhlocolitis in scid mice. We recently isolated a urease-negative Helicobacter sp. (H. sp.) that also induced proliferative typhlocolitis in pilot studies in scid mice. To determine the pathogenic potential of H. sp. in immunocompromised and immunocompetent mice, 5-week old male A/J or Tac:Icr:Ha(ICR)-scidfRF mice were inoculated by intraperitoneal (IP) injection with approximately 3 x 10(7) colony-forming units (CFU) of H. sp. Mice were necropsied at various time points postinoculation (PI). Sham-inoculated mice had no clinical, gross, or histopathological lesions. In contrast, scid mice inoculated IP with H. sp. had severe hemorrhagic diarrhea and decreased weight gain at 2, 7, and 18 weeks postinoculation (PI), with severe proliferative typhlocolitis, phlebothrombosis, and hepatitis. A/J mice had no clinical signs, but had mild to moderate proliferative typhlocolitis and moderate to marked cholangiohepatitis at 7 and 24 weeks PI. A/J mice infected with H. sp. developed robust immune responses of a predominant Th1 type. This report demonstrates that infection with a urease-negative helicobacter can cause inflammatory bowel disease (IBD) and hepatitis in scid and immunocompetent A/J mice. These results provide a new model of IBD and cholangio-hepatitis associated with a specific urease-negative, novel H. species.

Adaptation of bacteria to the intestinal niche: probiotics and gut disorder

The gastrointestinal tract is a complex ecosystem host to a diverse and highly evolved microbial community composed of hundreds of different microbial species. The interactions that occur between this complex microbial community and the human host have become the focus of scientific research due to increases in the incidence of illnesses associated with deficient or compromised microflora (e.g., gastrointestinal tract infections, inflammatory bowel disease (Crohn's disease and ulcerative colitis), irritable bowel syndrome, antibiotic-induced diarrhea, constipation, food allergies, cardiovascular disease, and certain cancers). Effective multidisciplinary research programs now complement conventional microbiology with molecular ecology techniques to provide culture-independent analysis of the gastrointestinal ecosystem. Furthermore, as we acquire an understanding of gut microflora composition and processes such as intestinal adherence, colonization, translocation, and immunomodulation, we are also elucidating mechanisms by which these can be influenced. This knowledge not only allows scientists to define the activities and interactions of "functional food"-borne beneficial bacteria in the gut, but will also provide the scientific basis for the development of innovative biotechnology-based products tailored to prevent specific diseases and promote overall human gastrointestinal health.

IgG subclasses of anti Saccharomyces cerevisiae antibody in inflammatory bowel disease

Elevation of serum anti Saccharomyces cerevisiae antibody (ASCA) has been reported in patients with Crohn's disease. We analysed the subclasses of Immunoglobulin (Ig) G reaction in ASCA in sera from patients with inflammatory bowel disease, healthy controls, and patients with intestinal Behçet's disease. Serum samples were obtained from 29 patients with Crohn's disease, 30 patients with ulcerative colitis, 7 patients with intestinal Behçet's disease, and 12 healthy controls. Serum IgG subclasses IgG1, IgG2, IgG3, and IgG4 of ASCA were analysed using ELISA. IgG4 ASCA was significantly increased in patients with inflammatory bowel disease. In patients with intestinal Behçet's disease, IgG1, IgG3, and IgG4 ASCA were increased. Differential responses, in terms of subclasses in ASCA, were found in patients with inflammatory bowel disease and patients with intestinal Behçet's disease, which may represent different pathophysiologies of these intestinal inflammatory diseases.

Comparative study of ASCA (Anti-Saccharomyces cerevisiae antibody) assays in inflammatory bowel disease

BACKGROUND & AIMS

Anti-Saccharomyces cerevisiae antibody (ASCA) is a serologic marker associated with Crohn's disease (CD). Although there is still discussion on its clinical value, several companies each promote their own ASCA assay to be used in the gastroenterologist's practice at considerable expense. The aim of this study was to determine whether different ASCA assays agree sufficiently well for the results to be used interchangeably.

METHODS

Blood obtained from a large cohort of IBD patients with inflammatory bowel disease (IBD; 100 with CD, 100 with ulcerative colitis [UC]) and 178 controls (100 healthy blood donors and 78 patients with non-IBD diarrheal illnesses) was studied with 4 different ASCA assays. Sensitivity, specificity, and positive predictive value were compared. Agreement between assays was evaluated.

RESULTS

Sensitivity of ASCA for CD ranged between 41% and 76%. Sensitivity was inversely related to specificity and positive predictive value. Results correlated well overall (range = 0.54-0.90) and the different ROC curves showed good agreement. When recalculated cutoff points were used, interchangeability increased. However, large differences were seen when absolute values were compared.

CONCLUSIONS

A large range in sensitivities and specificities of ASCA for CD is seen with different ASCA assays, mainly as a consequence of the cutoff value chosen for each individual assay. Although agreement between and within assays is good, caution is important when absolute values are used. Standardization of ASCA measurements is greatly needed.

Enteric bacteria, lipopolysaccharides and related cytokines in inflammatory bowel disease: biological and clinical significance

Ulcerative colitis (UC) and Crohn's disease (CD) [inflammatory bowel disease (IBD)] are both characterized by an exaggerated immune response at the gut associated lymphoreticular tissue level. Such an abnormal and dysregulated immune response may be directed against luminal and/or enteric bacterial antigens, as also supported by murine models of inflammatory bowel disease (IBD) caused by organisms such as Citrobacter rodentium and Helicobacter hepaticus. Bacterial endotoxins or lipopolysaccharides (LPS) have been detected in the plasma of IBD patients and an abnormal microflora and/or an increased permeability of the intestinal mucosa have been invoked as cofactors responsible for endotoxemia. At the same time, the evidence that phagocytosis and killing exerted by polymorphonuclear cells and monocytes and the T-cell dependent antibacterial activity are decreased in IBD patients may also explain the origin of LPS in these diseases. In IBD, pro-inflammatory cytokines and chemokines have been detected in elevated amounts in mucosal tissue and/or in peripheral blood, thus suggesting a monocyte/macrophage stimulation by enteric bacteria and/or their constituents (e.g. LPS). On these grounds, in experimental models and in human IBD, anti-cytokine monoclonal antibodies and interleukin receptor antagonists are under investigation for their capacity to neutralize the noxious effects of immune mediators. Finally, the administration of lactobacilli is beneficial in human IBD and, in murine colitis, this treatment leads to a normalization of intestinal flora, reducing the number of colonic mucosal adherent and translocated bacteria.

Protection from gastrointestinal diseases with the use of probiotics

Probiotics are nonpathogenic microorganisms that, when ingested, exert a positive influence on the health or physiology of the host. They can influence intestinal physiology either directly or indirectly through modulation of the endogenous ecosystem or immune system. The results that have been shown with a sufficient level of proof to enable probiotics to be used as treatments for gastrointestinal disturbances are 1) the good tolerance of yogurt compared with milk in subjects with primary or secondary lactose maldigestion, 2) the use of Saccharomyces boulardii and Enterococcus faecium SF 68 to prevent or shorten the duration of antibiotic-associated diarrhea, 3) the use of S. boulardii to prevent further recurrence of Clostridium difficile-associated diarrhea, and 4) the use of fermented milks containing Lactobacillus rhamnosus GG to shorten the duration of diarrhea in infants with rotavirus enteritis (and probably also in gastroenteritis of other causes). Effects that are otherwise suggested for diverse probiotics include alleviation of diarrhea of miscellaneous causes; prophylaxis of gastrointestinal infections, which includes traveler's diarrhea; and immunomodulation. Trials of gastrointestinal diseases that involve the ecosystem are currently being performed, eg, Helicobacter pylori infections, inflammatory bowel disease, and colon cancer.

Results of multiple diagnostic tests for Mycobacterium avium subsp. paratuberculosis in patients with inflammatory bowel disease and in controls

Mycobacterium avium subsp. paratuberculosis has been incriminated as a cause of Crohn's disease (CD); however, studies to date have been relatively small and generally only used a single diagnostic assay. The objective of the study was to reexamine the association of M. avium subsp. paratuberculosis and CD using multiple diagnostic tests. Five methods were used to detect M. avium subsp. paratuberculosis infections in 439 inflammatory bowel disease (IBD) patients and 324 control subjects in the United States and Denmark. Most assays were adaptations of diagnostic tests for this infection performed routinely on animals. PCR for IS900, a genetic element unique to M. avium subsp. paratuberculosis, was positive significantly more often on resected bowel and lymph node tissues from CD patients (19.0%) and ulcerative colitis (UC) patients (26.2%) than from controls (6. 3%) (P < 0.05). Positive IS900 PCR results occurred more often in U. S. than in Danish IBD patients, 32.0 versus 13.3% (P = 0.025). The majority of Danish patients were bacillus Calmette-Guérin (Mycobacterium bovis BCG) vaccinated (CD, 77.5%; UC, 86.6%; controls, 83.0%) whereas none of the U.S. patients with IBD and only 2% of U. S. controls were vaccinated. Among Danish IBD patients, positive PCR findings were four times more common among subjects who were not BCG vaccinated (33.3%) than among BCG vaccinates (8.8%, P = 0.02). Culture of the same tissues tested by PCR using modified BACTEC 12B medium failed to grow M. avium subsp. paratuberculosis from patients or controls. U.S. CD patients had the highest serological evidence (enzyme-linked immunosorbent assay [ELISA] for serum antibodies) of M. avium subsp. paratuberculosis infection (20.7% of patients positive) which was higher than for all UC patients studied (6.1%) or healthy controls (3.8%, P < 0.005). Among Danish patients alone, however, no significant differences in rates of ELISA-positive results among CD, UC, or control patients were found. For 181 study subjects, both IS900 PCR and ELISA were performed. Although 11 were ELISA positive and 36 were PCR positive, in no instance was a patient positive by both tests, suggesting that these states are mutually exclusive. Evaluation of cytokine-mediated immune responses of IBD patients was complicated by the influence of immunosuppressive therapy given most IBD patients. Gamma interferon (IFN-gamma) release by peripheral blood leukocytes after M. avium purified protein derivative PPD antigen stimulation showed significantly lower responses in CD patients than in UC patients or controls in both U.S. (by ex vivo assay) and Danish (by in vitro assay) populations (P < 0.05). Interleukin-5 responses were not different among CD, UC, or control groups. Collectively, the PCR, ELISA, and IFN-gamma tests for M. avium subsp. paratuberculosis together with the unexpected observation that BCG vaccination influenced M. avium subsp. paratuberculosis detection, lead us to conclude that M. avium subsp. paratuberculosis, or some similarly fastidious mycobacterial species, infects at least a subset of IBD patients. Whether the infection is primary (causal) or secondary, it may contribute to the etiopathogenesis of IBD.

Helicobacter hepaticus infection triggers inflammatory bowel disease in T cell receptor alphabeta mutant mice

The T cell receptor alpha chain-deficient (TCR alpha-/-) and TCR beta chain-deficient (TCR beta-/-) mice develop chronic intestinal inflammation that resembles inflammatory bowel disease by 3 to 4 months of age. The objective of the study reported here was to determine the role of infection with the bacterial pathogen Helicobacter hepaticus in the pathogenesis of disease in TCR alphabeta mutant mice. The H. hepaticus-infected TCR alphabeta mutant mice were rederived by use of embryo transfer to produce Helicobacter-free animals. Helicobacter-free TCR alpha-/-, TCR beta-/-, and TCR alpha-/- beta-/- mice were inoculated with H. hepaticus. Experimentally infected mice and uninfected control mice were examined for intestinal lesions at 3, 6, and 9 months after inoculation. The TCR alphabeta mutant mice inoculated with H. hepaticus developed intestinal epithelial cell hyperplasia and mucosal inflammation. By 6 months after inoculation, infected animals had moderate cecal and colonic lesions. Helicobacter-free TCR alpha-/- mice, but not TCR beta-/- or TCR alpha-/- x beta-/- mice, also developed H. hepaticus-independent colitis by 9 months after inoculation. Infection with H. hepaticus is sufficient to cause chronic proliferative intestinal inflammation in TCR alphabeta mutant mice. However, H. hepaticus infection is not necessary for intestinal disease in TCR alpha-/- mice.

Cells and cytokines in the pathogenesis of inflammatory bowel disease: new insights from mouse T cell transfer models

Recently, a number of experimental models of human inflammatory bowel disease (IBD) of immunological basis have been developed. These have proven useful tools in the study of IBD, allowing a more detailed dissection of the pathogenesis of the disease. Studies from these models have revealed new, important knowledge about environmental factors, cell subset, cytokines and effector molecules in the pathogenesis of IBD. This review focuses on recent advances in the understanding of the development of IBD obtained from adoptive CD4+ T cell transfer models of the disease.

Genotyping of Bacteroides fragilis isolates from stool specimens by arbitrarily-primed-PCR

In order to determine genetic relatedness of Bacteroides fragilis isolates from different clinical sources, arbitrarily primed polymerase chain reaction (PCR) (AP-PCR) was used to compare 17 strains isolated from patients with inflammatory bowel disease (IBD) and 20 strains isolated from foals with diarrhea. Three reference ATCC strains were also analyzed. Eighteen unique types were identified with a 22-mer arbitrary primer (ERIC-2) among the 20 patient isolates. Types 1 (enterotoxigenic) and 9 (nonenterotoxigenic), were each found in the stools of two patients. All other isolates showed a distinct and unique DNA banding pattern indicating a high degree of genotypic variability. Eleven types were identified among the foal isolates. Type 20, a nonenterotoxigenic type, was present in 30% of the foals. No correlation was found between the human and horse isolates. No clear relationship between a disease state (diarrhea or IBD) and specific types was observed. AP-PCR will be useful as a rapid method to determine genetic relatedness and in future epidemiologic studies of diarrheal diseases due to B. fragilis.

Presence of bacterial 16S ribosomal RNA gene segments in human intestinal lymph follicles

BACKGROUND

There is currently no information regarding microbial agents inside the intestinal lymph follicles.

METHODS

Biopsy or resected specimens, mostly from macroscopically normal areas, were sectioned with a cryostat. DNA was extracted from microdissected samples, exclusively from the lymph follicle. Amplification of DNA was performed using universal primers designed from conserved regions of bacterial 16S ribosomal RNA (rRNA). Several clones with inserts of around 400 base pairs were subjected to DNA sequence analysis followed by a database homology search.

RESULTS

Bacterial 16S rRNA gene segments were detected in the lymph follicle in 2 of 14 (14%) non-inflammatory bowel disease (IBD) cases, 4 of 14 (28%) Crohn disease cases, and in 2 of 5 (40%) ulcerative colitis cases. Nineteen 16S rRNA gene segments were recognized in the eight positive cases. Five segments showed 100% identity to known bacterial 16S rRNAs, namely staphylococcus species, Streptococcus sanguis, and Paracoccus marcusii. However, the other 14 segments showed below 100% identity, indicating either the presence of unknown bacteria or of bacteria without known DNA data. No single identified or unidentified bacterium, characteristic of IBD, including Mycobacterium paratuberculosis and Listeria monocytogenes, was detected.

CONCLUSIONS

The present study confirms the presence of bacterial 16S rRNA gene segments in human intestinal lymph follicles and paves the way for new investigations into the microbiology of the lymph follicle. Whether or not bacteria inside the lymph follicle is a primary stimulus in IBD has yet to be clarified.

Probiotics in infective diarrhoea and inflammatory bowel diseases

Bacteria are present throughout the gastrointestinal tract, but their pattern and concentration vary greatly. Probiotics are living organisms that supply beneficial health effects to the host. So far the beneficial effects of probiotics have been shown, almost exclusively, under poorly defined experimental conditions. There are little convincing data from well-designed, double-blind controlled trials supporting health-promoting effects. The use of probiotics to treat gastrointestinal infections has produced contrasting results. Apart from information on rotavirus infection in children, there is no convincing evidence from controlled studies on the efficacy of probiotics in the prevention or treatment of infective diarrhoea. However, experimental and clinical studies suggest that there are potential therapeutic roles for probiotics in the treatment of inflammatory bowel diseases. This review focuses on the available data concerning the mechanisms of action of probiotics, and on the results from clinical studies using probiotics to treat infective diarrhoea and inflammatory bowel disease.

Assessment of the prevalence of infection with Helicobacter pylori in patients with inflammatory bowel disease

OBJECTIVE

To determine the prevalence of Helicobacter pylori in patients with inflammatory bowel disease (IBD) and compare this to the prevalence in a control population with non-organic bowel symptoms, and to investigate the effect of sulphasalazine and other 5-aminosalicylic acid (5-ASA) drugs on the prevalence of H. pylori in IBD patients.

DESIGN

Prospective, controlled trial.

SETTING

Gastroenterology out-patient department, City General Hospital, North Staffordshire Hospitals NHS Trust, Stoke-on-Trent.

PARTICIPANTS

The population comprised 51 patients with ulcerative colitis, 42 patients with Crohn's disease and 40 patients with irritable bowel syndrome as controls. Patients with X-ray- and/or biopsy-proven disease were eligible to be entered into the study.

INTERVENTIONS

Subjects filled in a detailed questionnaire, were assessed for seropositivity of H. pylori and underwent a C13 urea breath test (UBT).

MAIN OUTCOME MEASURES

Seropositivity for H. pylori and a positive C13 UBT result.

RESULTS

A quarter of the irritable bowel syndrome controls were seropositive for H. pylori. Of the ulcerative colitis patients, 21.6% were currently H. pylori-positive on C13 UBT; 17.6% of the ulcerative colitis patients who had been previously treated with sulphasalazine were positive while 23.1% of the ulcerative colitis patients who had been treated with a non-sulphasalazine 5-ASA drug were positive. Of the Crohn's patients, 11.9% were currently H. pylori-positive; 3.6% of the Crohn's patients who had been previously treated with sulphasalazine were positive while 12.5% of the Crohn's patients who had been treated with a non-sulphasalazine 5-ASA drug were positive.

CONCLUSIONS

Patients with IBD and Crohn's disease in particular were less likely to be H. pylori-positive than controls. Sulphasalazine treatment further decreased the prevalence of H. pylori, although the reduced prevalence of H. pylori in IBD patients could not be accounted for by this alone.

The role of the resident intestinal flora in acute and chronic dextran sulfate sodium-induced colitis in mice

OBJECTIVE

There is increasing evidence that the intestinal microflora plays an important role in the pathogenesis of inflammatory bowel disease. In the present study, we examined the role of the resident intestinal flora in our model of dextran sulfate sodium (DSS)-induced acute and chronic colitis in mice.

METHODS

Acute colitis was induced in BALB/c mice with 5% DSS in their drinking water for 7 days. Chronic colitis was established after four cycles of feeding 5% DSS for 7 days and water for 10 days. For eliminating intestinal bacteria, mice were injected intraperitoneally with metronidazole and ciprofloxacin. We analysed four parameters: (1) body weight, (2) length of the colon, (3) histological score, and (4) myeloperoxidase activity.

RESULTS

In acute DSS colitis treatment with antibiotics led to an improvement of the histological parameters (epithelial damage, P< 0.05; inflammatory infiltrate, P< 0.05) and colon length (P < 0.0028). A significant reduction in granulocyte infiltration was indicated by a 52.6% reduced myeloperoxidase activity in colonic biopsies. By contrast, in chronic colitis, treatment of mice with antibiotics failed to show significant effects.

CONCLUSION

In acute DSS-induced colitis bacteria and/or bacterial products play a major role in initiation of inflammation but not in chronic DSS colitis.

Insights from mouse models of colitis

Emerging studies using mouse models of experimental colitis are defining the nature of the immunological disturbances that initiate inflammation and destruction of the intestine. A better understanding of disease-promoting and -suppressing CD4+ T cells is providing insight into the mechanisms controlling immune responses within the intestinal compartment. Moreover, a role for distinct T cell populations, including intraepithelial gammadelta T cells, in maintaining the physical integrity of the intestine was suggested by recent studies. Cytokine gene-knockout mice and anti-cytokine treatments remain important tools to define the pro- and anti-inflammatory functions of cytokines. These advances are fostering the design and evaluation of new therapeutic approaches that may eventually be applied to treat human inflammatory bowel disease.

Bacteroides fragilis enterotoxin gene sequences in patients with inflammatory bowel disease

We identified enterotoxigenic Bacteroides fragilis in stool specimens of patients with inflammatory bowel disease and other gastrointestinal disorders. The organism was detected in 11 (13.2%) of 83 patients with inflammatory bowel disease. Of 57 patients with active disease, 19.3% were toxin positive; none of those with inactive disease had specimens positive for enterotoxigenic Bacteroides fragilis gene sequences.

Etiology and pathophysiology of inflammatory bowel disease--environmental factors

Environmental factors play an important role in the pathophysiology of inflammatory bowel disease. There is a strong and consistent association between smoking and Crohn's disease, and between nonsmoking and ulcerative colitis. Despite extensive research, the exact pathophysiological mechanisms for these associations remain unclear. In spite of this, some clinical trials with nicotine-patches showed beneficial effects for the treatment of ulcerative colitis. Associations of Crohn's disease and ulcerative colitis with other environmental factors are weaker like the association with use of oral contraceptives or those less well investigated such as the association with childhood hygiene. Most studies suggesting a potential pathogenetic role of Mycobacterium paratuberculosis or an effect of tuberculostatic therapy in Crohn's disease could not be reproduced by others. Perinatal or childhood infections by viruses like measles are heavily debated, but not proven to be causal for inflammatory bowel disease. Coagulation disorders have been described as protecting from inflammatory bowel disease, suggesting hypercoagulability to be a pathogenetic factor. Some studies described that appendectomy may prevent the onset of ulcerative colitis in man and mice. Other environmental factors such as hydrogen sulfide, tonsillectomy, diet, blood transfusions, and Listeria also require confirmation. There are, however, convincing data from genetic animal models and twin studies that environmental factors as the intestinal bacterial flora interact with susceptible hosts to cause inflammatory bowel disease. Inflammatory bowel diseases have multifactorial etiologies, which require a differentiated approach for treatment and prevention.

Probiotics and inflammatory bowel diseases

The pathogenesis of inflammatory bowel diseases remains elusive. However, the resident luminal bacteria seem to be an important factor in their development and chronicity. There is evidence to suggest that inflammatory bowel diseases may represent an aggressive immunological response to the resident luminal flora, rather than an alteration in the normal flora. In prior research, probiotic bacteria were effective in managing certain acute diarrheal diseases, and investigators reported that certain Lactobacilli strains seem to have protective immunomodulating and bowel flora manipulating properties. We report the results of recent studies with probiotics in animal models, in which promising effects for the treatment of chronic inflammatory bowel disease, pouchitis, and ulcerative colitis were observed. Future research may clarify a precise role for probiotic bacteria in managing chronic inflammatory bowel diseases.

The intestinal mucus layer from patients with inflammatory bowel disease harbors high numbers of bacteria compared with controls

BACKGROUND & AIMS

Whether the bacterial flora contributes to the pathogenesis of inflammatory bowel disease (IBD) by increased penetration in mucus, increased adherence to epithelial cells, or invasion of the epithelium is unknown. We therefore studied the spatial distribution of bacteria in the mucosa of rectal biopsy specimens from patients with IBD and from controls.

METHODS

Rectal biopsy specimens from 19 patients with IBD and from 14 controls were studied by using nonradioactive ribosomal RNA in situ hybridization. Total mucosal surface length examined for each patient was measured, and the number of bacteria visualized was estimated semiquantitatively.

RESULTS

No bacteria were observed in biopsy specimens from 10 controls (71%) and 6 IBD patients (32%) (P = 0.04; odds ratio, 5.42; 95% confidence interval, 1.23-23.9). IBD rectal specimens contained significantly more bacteria than control samples (P = 0.004). Bacteria were localized within the mucus layer but did not adhere to the epithelial cells and were not present within the lamina propria. There was no correlation between the numbers of bacteria present and either the degree of inflammation or the use of anti-inflammatory agents or sulfasalazine compounds.

CONCLUSIONS

The intestinal mucus in IBD patients is less protective against the endogenous microflora than in controls, resulting in increased association of luminal bacteria with the mucus layer.

Isolation of Helicobacter canis from a colony of bengal cats with endemic diarrhea

On the basis of biochemical, phenotypic, and 16S rRNA analyses, Helicobacter canis was isolated from Bengal cats with and without chronic diarrhea. Because the cats were coinfected with other potential pathogens, including Campylobacter helveticus, and because H. canis was isolated from nondiarrheic cats, the causal role of H. canis in producing the diarrhea could not be proven. Histologically, the colons of the four affected cats were characterized by mild to moderate neutrophilic, plasmacytic, and histocytic infiltrates in the lamina propria. Rare crypt abscesses were also noted for three cats but were a more prominent feature of the colonic lesions noted for the fourth cat. This is the first observation of H. canis in cats and raises the possibility that H. canis, like H. hepaticus and H. bilis in mice, can cause inflammation of the colon, particularly in hosts with immune dysregulation. Further studies are needed to determine the importance of H. canis as a primary enteric pathogen in cats and the role of cats in the possible zoonotic spread of H. canis to humans.

Intestinal inflammation and the gut microflora

The idea that the enteric microflora play a role in the pathogenesis or pathophysiology of inflammatory bowel disease (IBD) is not new. Indeed, identification of an infective cause for chronic IBD, and particularly for Crohn's disease, has been the focus of extensive research efforts. During the 1990s, there has been a noticeable re-emergence of interest in the link between bacteria and functional bowel disorders, and the value of antibiotic therapy to treat gut inflammatory disorders. A variety of experimental evidence from both laboratory model systems and clinical investigations is reviewed with respect to a pivotal role for enteric bacteria in gut inflammation. The voluminous scientific literature on this subject precludes any comprehensive synopsis of the area; instead, pertinent studies are cited to illustrate the ability of bacteria and their products to evoke or exacerbate gut inflammation.

Probiotics: from myth to reality. Demonstration of functionality in animal models of disease and in human clinical trials

The enteric flora comprise approximately 95% of the total number of cells in the human body and are capable of eliciting immune responses while also protecting against microbial pathogens. However, the resident bacterial flora of the gastrointestinal tract (GIT) may also be implicated in the pathogenesis of several chronic conditions such as inflammatory bowel disease (IBD). The University College Cork-based Probiotic Research Group has successfully isolated and identified lactic acid bacteria (LAB) which exhibit beneficial probiotic traits. These characteristics include the demonstration of bile tolerance; acid resistance; adherence to host epithelial tissue; and in vitro antagonism of potentially-pathogenic micro-organisms or those which have been implicated in promoting inflammation. The primary objective of this report is to describe the strategy adopted for the selection of potentially effective probiotic bacteria. The study further describes the evaluation of two members of the resulting panel of micro-organisms (Lactobacillus salivarius subsp. salivarius UCC118 and Bifidobacterium longum infantis 35624) under in vitro conditions and throughout in vivo murine and human feeding trials. Specifically, an initial feeding study completed in Balb/c mice focused upon (i) effective delivery of the probiotic micro-organisms to the GIT and evaluation of the ability of the introduced strains to survive transit through, and possibly colonise, the murine GIT; (ii) accepting the complexity of the hostile GIT and faecal environments, development of a method of enumerating the introduced bacterial strains using conventional microbiological techniques; and (iii) assessment of the effects of administered bacterial strains on the numbers of specific recoverable indigenous bacteria in the murine GIT and faeces. Additional research, exploiting the availability of murine models of inflammatory bowel disease, demonstrated the beneficial effects of administering probiotic combinations of Lactobacillus salivarius UCC118 and Bifidobacterium longum infantis 35624 in prevention of illness-related weight loss. A further ethically-approved feeding trial, successfully conducted in 80 healthy volunteers, demonstrated that yoghurt can be used as a vehicle for delivery of Lactobacillus salivarius strain UCC118 to the human GIT with considerable efficacy in influencing gut flora and colonisation.

Current theories on the causes of inflammatory bowel disease

The understanding of the pathogenesis of CD and UC has greatly expanded over the last decade. The combination of abnormalities in the immune system, the contribution of nonimmune cells in the intestinal mucosa, a variety of genetic risk determinants, and random environmental factors may all be necessary to induce what clinically presents as IBD. It is likely that several agents can initiate an immune response that in the intestinal microenvironment and the genetic background of the patient finally leads to pathology.