Crohn's disease in people exposed to clinical cases of bovine paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) and Crohn's disease: the debate continues

Crohn's disease (CD) in humans and Johne's disease (JD) in ruminants share numerous clinical and pathologic similarities. As Mycobacteria avium subspecies paratuberculosis (MAP) is known to fulfill Koch's postulates as the cause of JD, there has been considerable debate over the past century about whether MAP also plays a role in CD. With recent advances in MAP identification techniques, we can now demonstrate a higher presence of MAP in CD patients compared to the general population. However, it remains unclear if MAP is playing a bystander role or is directly pathogenic in these patients. Studies have shown that there may be an immune response targeting MAP in these patients, which may underlie a pathologic role in CD. Clinical studies have yielded conflicting results as to whether anti-MAP therapy improves clinical outcomes in CD, leading to the lack of its inclusion within evidence-based clinical guidelines. Additionally, many of these studies have been small case series, with only a few randomized controlled trials published to date. In this article, we will discuss the historical context of MAP in CD, review clinical and laboratory data surrounding detection of MAP and possible pathogenesis in human disease, and suggest future directions which may finally provide some clarity to this debate.

The multifaceted virulence of adherent-invasive Escherichia coli

The surge in inflammatory bowel diseases, like Crohn's disease (CD), is alarming. While the role of the gut microbiome in CD development is unresolved, the frequent isolation of adherent-invasive Escherichia coli (AIEC) strains from patient biopsies, together with their propensity to trigger gut inflammation, underpin the potential role of these bacteria as disease modifiers. In this review, we explore the spectrum of AIEC pathogenesis, including their metabolic versatility in the gut. We describe how AIEC strains hijack the host defense mechanisms to evade immune attrition and promote inflammation. Furthermore, we highlight the key traits that differentiate AIEC from commensal E. coli. Deciphering the main components of AIEC virulence is cardinal to the discovery of the next generation of antimicrobials that can selectively eradicate CD-associated bacteria.

Putting Crohn's on the MAP: Five Common Questions on the Contribution of Mycobacterium avium subspecies paratuberculosis to the Pathophysiology of Crohn's Disease

For decades, Mycobacterium avium subspecies paratuberculosis (MAP) has been linked to the pathogenesis of Crohn's disease. Despite many investigations and research efforts, there remains no clear unifying explanation of its pathogenicity to humans. Proponents argue Crohn's disease shares many identical features with a granulomatous infection in ruminants termed Johne's disease and similarities with ileo-cecal tuberculosis. Both are caused by species within the Mycobacterium genus. Sceptics assert that since MAP is found in individuals diagnosed with Crohn's disease as well as in healthy population controls, any association with CD is coincidental. This view is supported by the uncertain response of patients to antimicrobial therapy. This report aims to address the controversial aspects of this proposition with information and knowledge gathered from several disciplines, including microbiology and veterinary medicine. The authors hope that this discussion will stimulate further research aimed at confirming or refuting the contribution of MAP to the pathogenesis of Crohn's disease and ultimately lead to advanced targeted clinical therapies.

Anti-Mycobacterium paratuberculosis (MAP) therapy for Crohn's disease: an overview and update

The role of Mycobacterium avium subspecies paratuberculosis (MAP) in the pathogenesis of Crohn's disease (CD) has been strongly debated for many years. MAP is the known aetiological agent of Johne's disease, a chronic enteritis affecting livestock. At present, due to the paucity of high-quality data, anti-MAP therapy (AMT) is not featured in international guidelines as a treatment for CD. Although the much-quoted randomised trial of AMT did not show sustained benefits over placebo, questions have been raised regarding trial design, antibiotic dosing and the formulation used. There are several lines of evidence supporting the CD and MAP association with uncontrolled and controlled trials demonstrating effectiveness, including a retrospective review of cases treated at our own institution. Here, we provide an overview of the evidence supporting and refuting AMT in CD before focussing on updates of the current research in the field, including the ongoing trials with the novel RHB-104 formulation and the MAP vaccine trial. While controversial, gastroenterologists are often asked about long-term combination antibiotic therapy for CD. There has been broadcast and social media coverage surrounding this, particularly with regard to current trials. Although patients should not be deterred from treatments of proven effectiveness, this review aims to help with commonly asked questions and highlights our own approach for the use of anti-MAP in specific circumstances.

Mycobacterium avium subspecies paratuberculosis - an important food borne pathogen of high public health significance with special reference to India: an update

This review underlines the public health significance of 'Indian Bison Type' of Mycobacterium avium subspecies paratuberculosis (MAP) and also its potential as 'zoonotic infection'. In the absence of control programs, bio-load of MAP is increasing and if we take total population of animals (500 million plus) and human beings (1.23 billion plus) into account, the number of infected animals and human beings will run into millions in India. Our research on screening of over 26,000 domestic livestock for MAP infection using 4 different diagnostic tests (microscopy, culture, ELISA and PCR), during last 31 years has shown that the average bio-load of MAP in the livestock population of India is very high (cattle 43%, buffaloes 36%, goats 23% and sheep 41%). 'Mass screening' of 28,291 human samples between 2008-2016 revealed also high bio-load of MAP. It has been proved that MAP is not in-activated during pasteurization and therefore live bacilli are continuously reaching human population by consumption of even pasteurized milk and other milk products. Live bacilli have also been recovered from meat products and the environment thus illustrating the potential of MAP as pathogen of public health concern. However, at present, there is inadequate scientific evidence to confirm a conclusive link between MAP infection and Johne's disease in ruminants and some cases of Crohn's disease in human beings.

Mycobacterium avium ssp. paratuberculosis detection in animals, food, water and other sources or vehicles of human exposure: A scoping review of the existing evidence

Mycobacterium avium ssp. paratuberculosis is the etiologic agent of Johne's disease in ruminants and is hypothesized to be an infectious cause of Crohn's disease, as well as some other human diseases. Due to key knowledge gaps, the potential public health impact of M. paratuberculosis is unknown. This scoping review aims to identify and characterised the evidence on potential sources and vehicles of M. paratuberculosis exposure for humans to better understand how exposure is likely to occur. Evidence from 255 primary research papers is summarized; most examined the prevalence or concentration of M. paratuberculosis in animals (farmed domestic, pets and wildlife) (n=148), food for human consumption (62) (milk, dairy, meat, infant formula) or water (drinking and recreational) and the environment (farm, pasture and areas affected by runoff water) (20). The majority of this research has been published since 2000 (Figure- abstract). Nine case-control studies examining risk factors for Crohn's disease highlighted significant associations with the consumption of processed meats and cheese, while direct contact with ruminants, high risk occupations (farmer, veterinarian), milk consumption and water source were factors not associated with the disease and/or M. paratuberculosis exposure status. Molecular epidemiology studies demonstrated strain-sharing between species. Produce and seafood were the only previously suggested sources of human exposure for which there was no supporting evidence identified in this scoping review. The results of this review indicate that ruminant populations from around the globe are infected with M. paratuberculosis and many non-ruminant species have also been found to carry or be infected with M. paratuberculosis. Several potential sources for human exposure to M. paratuberculosis were identified; however there remain important gaps in quantitative information on the prevalence and concentration of M. paratuberculosis in contaminated sources of exposure. This information is critical to understanding the risk of exposure, opportunities for risk mitigation interventions and modelling exposures to distill the importance of various sources of human exposure to M. paratuberculosis including direct contact with animals and the environment as well as consumption of contaminated foods and water. Results of this study may be used to prioritize future research and to support evidence-informed decision-making on the M. paratuberculosis issue.

Influence of environmental factors on the onset and course of inflammatory bowel disease

Numerous environmental factors have been linked with inflammatory bowel disease. These include smoking, diet, hygiene, drugs, geographical and psychosocial factors. These factors may either increase the risk of or protect against developing this condition and can also affect the course of illness in a positive or negative manner. A number of studies have examined the influence of environmental factors on inflammatory bowel diseases as a whole as well as on ulcerative colitis and Crohn’s disease separately. As there are differences in the pathogenesis of ulcerative colitis and Crohn’s disease, the effect of environmental factors on their onset and course is not always similar. Some factors have shown a consistent association, while reports on others have been conflicting. In this article we discuss the current evidence on the roles of these factors on inflammatory bowel disease, both as causative/protective agents and as modifiers of disease course.

The zoonotic potential of Mycobacterium avium ssp. paratuberculosis: a systematic review and meta-analyses of the evidence

This systematic review-meta-analysis appraises and summarizes all the available research (128 papers) on the zoonotic potential of Mycobacterium avium ssp. paratuberculosis. The latter has been debated for a century due to pathogenic and clinical similarities between Johne's disease in ruminants and Crohn's disease (108 studies) in humans and recently for involvement in other human diseases; human immunodeficiency virus (HIV) infection (2), sarcoidosis (3), diabetes mellitus type 1 (T1DM) (7) and type 2 (3), multiple sclerosis (5) and Hashimoto's thyroiditis (2). Meta-analytical results indicated a significant positive association, consistently across different laboratory methods for Crohn's disease [odds ratio (OR) range 4·26-8·44], T1DM (OR range 2·91-9·95) and multiple sclerosis (OR range 6·5-7·99). The latter two and the thyroiditis hypothesis require further investigation to confirm the association. Meta-regression of Crohn's disease studies using DNA detection methods indicated that choice of primers and sampling frame (e.g. general population vs. hospital-based sample) explained a significant proportion of heterogeneity. Other epidemiological studies demonstrated a lack of association between high-risk occupations and development of Crohn's disease. Due to knowledge gaps in understanding the role of M. paratuberculosis in the development or progression of human disease, the evidence at present is not strong enough to inform the potential public health impact of M. paratuberculosis exposure.

What Role Does Mycobacterium avium subsp. paratuberculosis Play in Crohn's Disease?

Crohn's disease (CD) is a chronic, debilitating inflammatory bowel disease with no etiological agent yet identified. Studies have demonstrated that the bacterium Mycobacterium avium subsp. paratuberculosis (MAP) is present in a high percentage of CD patients. Although MAP has been isolated from human specimens, current techniques fail to show the presence of MAP in 100 % of tissues or biopsies obtained from CD patient lesions, and thus MAP cannot meet Koch's postulate as the etiological agent of CD. In this report, the effect of genetic and immune factors as well as the presence of MAP as a potential environmental factor is analyzed.

Mycobacterium paratuberculosis as a cause of Crohn's disease

Crohn's disease is a chronic inflammatory bowel disease of unknown cause, affecting approximately 1.4 million North American people. Due to the similarities between Crohn's disease and Johne's disease, a chronic enteritis in ruminant animals caused by Mycobacterium avium paratuberculosis (MAP) infection, MAP has long been considered to be a potential cause of Crohn's disease. MAP is an obligate intracellular pathogen that cannot replicate outside of animal hosts. MAP is widespread in dairy cattle and because of environmental contamination and resistance to pasteurization and chlorination, humans are frequently exposed through contamination of food and water. MAP can be cultured from the peripheral mononuclear cells from 50-100% of patients with Crohn's disease, and less frequently from healthy individuals. Association does not prove causation. We discuss the current data regarding MAP as a potential cause of Crohn's disease and outline what data will be required to firmly prove or disprove the hypothesis.

Mycobacterium avium subspecies paratuberculosis in the etiology of Crohn’s disease, cause or epiphenomenon?

The origin of inflammatory bowel disease is unknown. Attempts have been made to isolate a microorganism that could explain the onset of inflammation, but no pathological agent has ever been identified. Johne’s disease is a granulomatous chronic enteritis of cattle and sheep caused by Mycobacterium avium subspecies paratuberculosis (MAP) and shows some analogies with Crohn’s disease (CD). Several studies have tried to clarify if MAP has a role in the etiology of CD. The present article provides an overview of the evidence in favor and against the “MAP-hypothesis”, analyzing the methods commonly adopted to detect MAP and the role of antimycobacterial therapy in patients with inflammatory bowel disease. Studies were identified through the electronic database, MEDLINE, and were selected based on their relevance to the objective of the review. The presence of MAP was investigated using multiple diagnostic methods for MAP detection and in different tissue samples from patients affected by CD or ulcerative colitis and in healthy controls. On the basis of their studies, several authors support a close relationship between MAP and CD. Although increasing evidence of MAP detection in CD patients is unquestionable, a clear etiological link still needs to be proven.

Detection of Antibodies and Confirmation of Mycobacterium avium Subspecies paratuberculosis Using Nested PCR in Bulk Milk Samples from Nakasongola and Sembabule Districts, Uganda

Mycobacterium avium subspecies paratuberculosis (MAP) is an emerging pathogen in many livestock and wildlife populations around the world. Concerns range from the serious economic impacts on livestock productivity to its suspected role in the human inflammatory bowel disease syndrome. Milk and faeces of infected animals are the main vehicles through which the organism spreads from infected to susceptible hosts. In this study, a survey was done in Nakasongola and Sembabule districts of Uganda involving a total of seven dairy collection centres to determine the prevalence of antibodies to MAP in bulk milk samples. The milk was tested with a commercial ELISA kit for MAP testing in milk. Positive and suspicious milk samples were further tested using nested PCR. Of the 257 milk samples tested, 11 (4.3%) were positive and five (1.9%) were suspicious. All the ELISA positive and suspicious milk samples were positive using nested PCR. The results show that MAP infection occurs in cattle from the two districts and highlight the need for a paratuberculosis control program in these and other districts where MAP infection has been reported.

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.

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.

The Broad Street pump revisited: dairy farms and an ongoing outbreak of inflammatory bowel disease in Forest, Virginia

We report an ongoing outbreak of ulcerative colitis and Crohn's disease in Forest, Virginia involving 15 unrelated children and teenagers who resided in close proximity to dairy farms. Some of our cases demonstrated serologic evidence of Mycobacterium avium subspecies paratuberculosis infection, suggesting its potential role as an etiologic agent.

High prevalence of Mycobacterium avium subspecies paratuberculosis ('Indian bison type') in animal attendants suffering from gastrointestinal complaints who work with goat herds endemic for Johne's disease in India

OBJECTIVES

In this study we aimed to estimate the prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) in animal attendants who were chronic colitis patients or who had inflammatory bowel disease and were suspected for Crohn's disease; these animal attendants worked with goat herds endemic for Johne's disease. Microscopic examination and culture tests were used. For comparison purposes a group of healthy human subjects (not suffering with colitis) was also screened.

METHODS

Stool samples obtained from 98 human subjects (58 animal attendants suspected for Crohn's disease and 40 healthy humans) were screened for the presence of MAP by microscopic examination and culture. Of the 58 animal attendants screened, 38 had abdominal pain, 29 had suffered episodes of diarrhea, 39 had experienced weight loss, 27 had fever, and 32 had a history of raw milk consumption. Animal attendants had had contact of variable duration with goat herds endemic for Johne's disease (1-5, 6-10, 11-15, and >15 years). Forty stool samples from healthy humans with no symptoms/history of contact with animals were also screened. IS900 PCR and IS1311 PCR restriction endonuclease analysis were used to characterize and genotype the MAP colonies.

RESULTS

MAP was recovered from 34 of the 98 human subject stool samples (34.7%). Of the 98 samples, 16.3% (n=16) were acid-fast. None of the 40 healthy human subjects were positive for MAP by microscopy, but five (12.5%) were positive for MAP by culture. Of the 58 animal attendants, 16 (27.6%) were positive by microscopy and 29 (50%) were positive by culture. MAP were recovered from 68.4% of animal attendants with abdominal pain, 72.4% of those with diarrhea, 71.8% of those with weight loss, 44.4% of those with fever, and 46.9% of those who had a history of raw milk consumption. Of the 29 culture-positive animal attendants, 48.3% had worked for >15 years, 27.6% for 11-15 years, 20.7% for 6-10 years, and 3.4% for 1-5 years with goat herds endemic for Johne's disease. Of the 34 culture isolates, 28 (82.4%) showed good quality DNA on agarose gel and were positive by IS900 PCR. Of the 28 IS900-positive DNA samples, 23 (82.1%) were genotyped as 'Indian bison type' and five (17.9%) as 'cattle type'.

CONCLUSIONS

The prevalence of MAP was higher in attendants suffering from gastrointestinal problems who worked with goat herds endemic for Johne's disease, than in humans with no history of contact with animals. The risk of developing gastrointestinal problems with clinical symptoms indistinguishable from inflammatory bowel disease was higher in humans who were in contact with goat herds endemic for Johne's disease as compared to healthy humans, and the risk was correlated with the duration of association with the endemic goat herds.

Mycobacterium avium subsp. paratuberculosis in dairy products, meat, and drinking water

Mycobacterium avium subsp. paratuberculosis (Map) is the cause of Johne's disease, a chronic infection of the gut, in ruminant animals that provide milk and/or meat for human consumption. Map also may be involved in Crohn's disease and type 1 diabetes in humans. Although the role of Map in human diseases has not been established, minimizing the exposure of humans to the organism is considered desirable as a precautionary measure. Infected animals can shed Map in feces and milk, and the organism can become disseminated in tissues remote from the gut and its associated lymph nodes. The presence of at least some Map in raw milk and meat and in natural waters is likely, but the numbers of Map in those foods and waters should be reduced through cooking or purification. The available information relating to Map in milk and dairy products, meats, and drinking water is reviewed here for assessment of the risks of exposure to Map from consumption of such foods and water.

Current perspectives on Mycobacterium avium subsp. paratuberculosis, Johne's disease, and Crohn's disease: a review

Mycobacterium avium subsp. paratuberculosis (MAP) causes the disease of cattle, Johne's. The economic impact of this disease includes early culling of infected cattle, reduced milk yield, and weight loss of cattle sold for slaughter. There is a possible link between MAP and Crohn's disease, a human inflammatory bowel disease. MAP is also a potential human food borne pathogen because it survives current pasteurization treatments. We review the current knowledge of MAP, Johne's disease and Crohn's disease and note directions for future work with this organism including rapid and economical detection, effective management plans and preventative measures.

Ulcerative colitis and Crohn's disease: is Mycobacterium avium subspecies paratuberculosis the common villain?

Mycobacterium avium, subspecies paratuberculosis (MAP) causes a chronic disease of the intestines in dairy cows and a wide range of other animals, including nonhuman primates, called Johne's ("Yo-knee's") disease. MAP has been consistently identified by a variety of techniques in humans with Crohn's disease. The research investigating the presence of MAP in patients with Crohn's disease has often identified MAP in the "negative" ulcerative colitis controls as well, suggesting that ulcerative colitis is also caused by MAP. Like other infectious diseases, dose, route of infection, age, sex and genes influence whether an individual infected with MAP develops ulcerative colitis or Crohn's disease. The apparently opposite role of smoking, increasing the risk of Crohn's disease while decreasing the risk of ulcerative colitis, is explained by a more careful review of the literature that reveals smoking causes an increase in both diseases but switches the phenotype from ulcerative colitis to Crohn's disease. MAP as the sole etiologic agent of both ulcerative colitis and Crohn's disease explains their common epidemiology, geographic distribution and familial and sporadic clusters, providing a unified hypothesis for the prevention and cure of the no longer "idiopathic" inflammatory bowel diseases.

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.

Lack of association between the occurrence of Crohn's disease and occupational exposure to dairy and beef cattle herds infected with Mycobacterium avium subspecies paratuberculosis

A cross-sectional survey was conducted to identify associations between Crohn's disease (CD) and Mycobacterium avium ssp. paratuberculosis (Map) exposure. A questionnaire was used to collect information on exposure to cattle infected with Map, and personal and family history of CD in dairy and beef cattle producers with and without Map-infected herds, and in veterinarians who did or did not have contact with Map-infected herds. Cases of CD were selected from respondents and matched 1:4 with controls on occupation, age, and sex. Multivariable conditional logistic regression was used to assess associations between Map exposure and CD. There were 3 cases of CD in 702 producers and 4 cases in 774 veterinarians, yielding a prevalence of 0.47%. No association was found between exposure to JD and CD in any phase of the analysis. However, the number of cases of CD is not large and limits the power to detect important differences.

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.

Advances in epidemiology and diagnosis of inflammatory bowel diseases

The etiology of chronic inflammatory bowel diseases (IBD) remains unknown. Understanding IBD epidemiology helps to identify at-risk individuals, to appreciate the changing demographic profile of IBD, and to interpret theories of IBD pathogenesis. This article reviews recent advances in epidemiology and diagnostics. The importance of Clostridium difficile is highlighted. State-of-the-art IBD diagnostic modalities include serology, fecal markers, and advanced radiologic or endoscopic techniques. These include wireless capsule endoscopy, balloon enteroscopy, chromoendoscopy, high-magnification endoscopy, and MRI. The increasing number of available modalities requires appreciation of their indications, strengths, and limitations. This article discusses these issues relevant to the clinician.

Prevalence of infectious pathogens in Crohn's disease

The importance of infectious pathogens in Crohn's disease (CD) is still under debate. Therefore, we examined a panel of potential viral and bacterial pathogens in a large series of CD patients and controls. Archival tissue from 76 patients, 56 with CD and 20 control patients, with normal colon mucosa (n=10) and non-steroid anti-inflammatory drug (NSAID)-induced colitis (n=10) were examined using PCR-based detection methods for human cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus 1, 2 (HSV1,2), adenovirus (AD), varicella-zoster virus (VZV), human herpes virus 6 (HHV6), human herpes virus 8 (HHV8), Mycobacterium tuberculosis complex (Mtbc), atypical mycobacteria (nM/MG1), including Mycobacterium avium (subspecies paratuberculosis, MAP), Stenotrophomonas maltophilia (Sm), and Yersinia enterocolitica (Ye). In CD patients, positive PCR results were achieved in 19 cases (34%). Sm was most frequent in 10 of 56 cases (17.9%) followed by EBV (6/56, 10.7%), nM/MG1 (4/56, 7.1%), including MAP, HHV6, and CMV (2/56, 3.6%), and finally Mtbc and AD (1/56, 1.8%). The control patients showed positive PCR results in 12 patients (12/20, 60%), nine of them with only weak signals, suggesting a persistent infection. In addition, we compared typical pathomorphological features of CD patients with the PCR results and found a significant correlation between EBV infection and mural abscesses (P=0.014). Our data demonstrate that several potential pathogens can be detected in a sizeable fraction of specimens from patients with CD, but also in control patients, suggesting that the analyzed infectious pathogens may be associated with the disease, but do not represent an obligatory cause.

Mycobacterium avium subspecies paratuberculosis and its relationship with Crohn’s disease

The hypothesis postulating that Mycobacterium avium paratuberculosis (MAP) is the cause of Crohn’s disease (CD) has been circulating for many years. Advances in molecular techniques, such as polymerase chain reaction and culture methods, have enabled researchers to demonstrate that there is an association between MAP and CD. Recently, genome-wide association studies have identified novel susceptibility genes for CD, which are critical for generation of an adaptive immune response that is protective against intracellular pathogens, including M. tuberculosis infection. However, the role of MAP as a cause of CD suffered a setback with the report that administration of antimycobacterial therapy failed to lead to a sustained response in CD patients. Accordingly, this review sought neither to confirm nor refute this, but instead to survey recent literature on the role of MAP in CD.

Impact of lactose containing foods and the genetics of lactase on diseases: an analytical review of population data

Dairy foods (DFs) contain complex ingredients that could affect different diseases. The control of lactose digestion phenotypically divides populations into those who can [lactase persistent (LP)] and those who cannot [lactase nonpersistent (LNP)] assimilate lactose. LNP subjects, however, can adapt to lactose intolerance through intestinal bacteria. The DF/LNP status interactions may function as disease risk modifiers. We evaluated the relationship between DF and LNP with colorectal, breast, prostate, ovarian, lung, and stomach cancer and inflammatory bowel diseases (IBD; Crohn's disease and ulcerative colitis). Yearly per capita DF consumption, LNP national prevalence, cancer mortality, and incidence of IBD were obtained from several sources. A negative binomial regression model was used to derive incremental risks. There were statistically significant (P <or= 0.05) increases in risk for colorectal and prostate cancer and ulcerative colitis with DFs and a statistically significant decreased risk for stomach cancer. There were trends (P<0.1) for lung and ovarian cancers and Crohn's disease. As LNP prevalence increased, stomach cancer risk increased, whereas risks of all other conditions decreased (P<0.01). In 3 cancers (prostate, ovarian, and breast), meta-analyses of case-based studies support ecological data. In colorectal cancer, on the contrary, meta-analyses of case-based studies suggest protection. The possible importance of distinguishing LNP/LP status in studies is discussed.

The zoonotic potential of Mycobacterium avium spp. paratuberculosis: a systematic review

BACKGROUND

The zoonotic potential of Mycobacterium avium ssp. paratuberculosis (MAP) has been debated for almost a century because of similarities between Johne's Disease (JD) in cattle and Crohn's disease (CD) in humans. Our objective was to evaluate scientific literature investigating the potential association between these two diseases (MAP and CD) and the presence of MAP in retail milk or dairy products using a qualitative systematic review.

METHOD

The search strategy included 19 bibliographic databases, 8 conference proceedings, reference lists of 15 articles and contacting 28 topic-related scientists. Two independent reviewers performed relevance screening, quality assessment and data extraction stages of the review.

RESULTS

Seventy-five articles were included. Among 60 case-control studies that investigated the association between MAP and CD, 37 were of acceptable quality. Twenty-three studies reported significant positive associations, 23 reported non-significant associations, and 14 did not detect MAP in any sample. Different laboratory tests, test protocols, types of samples and source populations were used in these studies resulting in large variability among studies. Seven studies investigated the association between CD and JD, two challenge trials reported contradictory results, one cross-sectional study did not support the association, and four descriptive studies suggested that isolated MAP is often closely related to cattle isolates. MAP detection in raw and pasteurized milk was reported in several studies.

CONCLUSIONS

Evidence for the zoonotic potential of MAP is not strong, but should not be ignored. Interdisciplinary collaboration among medical, veterinary and other public health officials may contribute to a better understanding of the potential routes of human exposure to MAP.

New global map of Crohn's disease: Genetic, environmental, and socioeconomic correlations

Seventy-five years after the initial characterization of Crohn's disease (CD), much remains obscure about its etiology. The authors sought to evaluate the incidence trends of the last 25 years worldwide, and the existence of potential correlations with genetic, environmental, and socioeconomic factors that could be etiologically implicated in the pathogenesis of CD. Relevant medical literature for individual countries on the incidence of CD, on the incidence of associated genetic mutations, and on the incidence of suggested etiologic infectious agents such as Mycobacterium avium paratuberculosis were retrieved from published medical literature, reports from relevant international congresses, and through official reports from national health authorities. Increasing trends have been observed almost worldwide, with a broad north-south gradient still prevailing in Europe. Distinct regions of New Zealand, Canada, Scotland, France, the Netherlands, and Scandinavia represent the highest incidence areas. Industrialized status and affluence are the common denominators between endemic areas, but are too broad as terms to strongly indicate any particular etiological role. The increasing trends observed in Asia still account for a low prevalence of the disease and may represent increased detection and diagnostic ability of local health systems. Genetic associations are variably reproduced worldwide, in a manner inconsistent with a strong etiologic relationship. Data on paratuberculosis incidence are scarce, and the existing ones are ambivalent regarding an even indirect correlation between CD and an infectious trigger.

The evidence for Mycobacterium paratuberculosis in Crohn's disease

PURPOSE OF REVIEW

Though long hypothesized, the putative link between Mycobacterium avium paratuberculosis and Crohn's disease remains neither confirmed nor refuted. This article reviews published contributions that directly or indirectly address this question.

RECENT FINDINGS

Epidemiologic studies, looking for M. avium paratuberculosis DNA in Crohn's tissue, show a strong association between the agent and this disease. Supporting data, however, are presently inconclusive on a causal role. Genetic studies provide indirect support for a role of mycobacteria in Crohn's disease, by identifying susceptibility genes that encode proteins implicated in innate immunity to intracellular bacteria. Clinical trial data support at least a short-term benefit for antimycobacterial therapy in Crohn's disease, but the microbial specificity of this response is presently unknown.

SUMMARY

There appears to be a strong association between M. avium paratuberculosis and Crohn's disease, but the causality of this association is unknown. Consequently, the therapeutic implications of this association require further study. A number of critical questions about the biology of M. avium paratuberculosis remain unanswered. Data from studies of this organism, and its interaction with the immune system, can help address proposed reasons for or against a role of M. avium paratuberculosis in the etiology of Crohn's disease.

Antigen discovery: A postgenomic approach to paratuberculosis diagnosis

Paratuberculosis is a chronic enteritis caused in domestic and wild ruminant species by Mycobacterium avium subsp. paratuberculosis (MAP) that is responsible for major economic losses to the agricultural industry. To date, no satisfactory therapeutic, vaccine, or diagnostic tools are available, globally impairing all control programs. In this study, we have undertaken a large-scale postgenomic analysis of MAP proteins, to identify specific antigens that could potentially improve the diagnosis of paratuberculosis. Two complementary approaches were implemented, the first one consisting in the systematic proteomic identification of proteins present in MAP culture filtrates (CFs), followed by the selection of MAP-specific proteins by BLAST query on available mycobacterial genomes. The resulting database represents the first established secretome of MAP and a useful source of potentially specific antigens. The second approach consisted in the immunoproteomic analysis of both MAP extracts and CFs, using sera from MAP-infected and uninfected cattle. Combining results obtained with both approaches resulted in the identification of 25 candidate diagnostic antigens. Five of these were tested in an ELISA assay for their diagnostic potential, on a limited panel of field sera, and the combination of three of them competed in performance with available commercial assays, reaching a test sensitivity of 94.74% and specificity of 97.92%.