Detection of Mycobacterium avium subspecies paratuberculosis in Crohn's diseased tissues by in situ hybridization

Role of intestinal flora characteristics in traditional Chinese medicine-based diagnosis and treatment of spleen and stomach diseases

Abnormal rise and fall of spleen and stomach Qi will lead to a series of spleen and stomach diseases. Spleen-deficiency syndrome and damp-heat syndrome are important traditional Chinese medicine (TCM) syndromes of spleen-stomach diseases, and they also correlate with imbalance of intestinal flora. Given the correlation between spleen and stomach diseases and intestinal flora, this paper discusses the changes of intestinal flora in common spleen and stomach diseases by reviewing the relevant literature, in order to demonstrate the role of intestinal flora in the diagnosis and treatment of TCM syndromes and promote the objectification of TCM syndromes.

Chronic regional intestinal inflammatory disease: A trans-species slow infection?

Crohn's disease and ulcerative colitis in humans and paratuberculosis in domestic and wild ruminants can be defined as chronic regional intestinal inflammatory diseases (CRIID). This review is a literature overview on these diseases in humans, non-human primates, dogs, cats, rabbits, equids and ruminants with a focus on pathological and microbiological features aimed identifying common characteristics that could lead to a unified pathological classification for a better understanding of their mechanisms and causes. The result is a framework of inflammatory forms throughout the different species indicative of common mechanisms of the slow infection type characterized by a time course varying from weeks to months or even years, and where the inflammatory component would be more prominent in the intestinal interphase between host and environment and be morphologically characterized by an infiltrate ranging from lymphoplasmacytic to histiocytic. This should provide new insights for causation demonstration and therapeutic approaches in human IBD.

Dissecting the Interplay Between Intestinal Microbiota and Host Immunity in Health and Disease: Lessons Learned from Germfree and Gnotobiotic Animal Models

This review elaborates the development of germfree and gnotobiotic animal models and their application in the scientific field to unravel mechanisms underlying host-microbe interactions and distinct diseases. Strictly germfree animals are raised in isolators and not colonized by any organism at all. The germfree state is continuously maintained by birth, raising, housing and breeding under strict sterile conditions. However, isolator raised germfree mice are exposed to a stressful environment and exert an underdeveloped immune system. To circumvent these physiological disadvantages depletion of the bacterial microbiota in conventionally raised and housed mice by antibiotic treatment has become an alternative approach. While fungi and parasites are not affected by antibiosis, the bacterial microbiota in these "secondary abiotic mice" have been shown to be virtually eradicated. Recolonization of isolator raised germfree animals or secondary abiotic mice results in a gnotobiotic state. Both, germfree and gnotobiotic mice have been successfully used to investigate biological functions of the conventional microbiota in health and disease. Particularly for the development of novel clinical applications germfree mice are widely used tools, as summarized in this review further focusing on the modulation of bacterial microbiota in laboratory mice to better mimic conditions in the human host.

The human gastrointestinal tract and oral microbiota in inflammatory bowel disease: a state of the science review

Inflammatory bowel disease (IBD) includes a spectrum of diseases from ulcerative colitis (UC) to Crohn's disease (CD). Many studies have addressed the changes in the microbiota of individuals affected by UC and CD. A decrease in biodiversity and depletion of the phyla Bacteroidetes and Firmicutes has been reported, among others. Changes in microbial composition also result in changes in the metabolites generated in the gut from microbial activity that may involve the amount of butyrate and other metabolites such as H₂ S being produced. Other factors such as diet, age, or medication need to be taken into consideration when studying dysbiosis associated with IBD. Diverse bacterial species have been associated specifically or non-specifically to IBD, but none of them have been demonstrated to be its ethiological agent. Recent studies also suggest that micro-eukaryotic populations may also be altered in IBD patients. Last, but not least, viruses, and specially bacteriophages, can play a role in controlling microbial populations in the gastrointestinal tract. This may affect both bacterial diversity and metabolism, but possible implications for IBD still remain to be solved. Dysbiosis in the oral microbiome associated with IBD remains an emerging field for future research.

Gene Expression and Antimicrobial Activity of Bovine Macrophages in Response to Mycobacterium avium subsp. paratuberculosis

We evaluated gene expression and antimicrobial responses of bovine monocyte—derived macrophages incubated with Mycobacterium avium subsp. paratuberculosis (M. a. ptb), the causative agent of Johne's disease. Gene expression was evaluated by the use of human noncompetitive high-density oligonucleotide microarrays. Bovine messenger RNA hybridized with 14.2–18.2% of the 12,600 oligonucleotide probe sets. When macrophages incubated with M. a. ptb were compared with nonactivated control macrophages, macrophages activated by addition of interferon-γ and lipopolysaccharide, and macrophages incubated with Mycobacterium avium subspecies avium (M. a. a), 47, 79, and 27 genes, respectively, were differentially expressed. Differential expression of six of these genes was confirmed using reverse transcriptase polymerase chain reaction. Several functional assays were performed to evaluate the potential relevance of differentially expressed genes to host defense. Macrophages phagocytizing M. a. a had a greater capacity to kill the organisms and to acidify phagosomes and a greater degree of apoptosis than did macrophages incubated with M. a. ptb. The results of these studies indicate that multiple genes and metabolic pathways are differentially expressed by macrophages ingesting mycobacterial organisms. Although the intracellular fate of mycobacterial organisms appears to be dependent on a complex interaction between macrophage and organism, phagosome acidification and apoptosis may play central roles in organism survival.

Altered Fecal Microbiota in Paediatric Inflammatory Bowel Disease

BACKGROUND AND AIMS

Several factors support the view of inflammatory bowel disease [IBD] origin in the host responsiveness to intestinal bacteria, although no single bacterial species has been shown as a causative agent in the pathogenesis. Our aim was to analyse the fecal microbiota of paediatric IBD patients at different stages of the disease. In addition, the characteristics of immune response to the bacterial isolates showing very low abundance in IBD were studied.

METHODS

Fecal samples [1-3 samples/child] were collected from 10 paediatric patients with crohn's disease [CD], and 12 with ulcerative colitis [UC] and from 8 healthy children, for polyphasic microbiological analysis (culture, real-time polymerase chain reaction [PCR], and denaturing gradient gel electrophoresis). In addition, in vitro cytokine responses of peripheral blood mononuclear cells to the bacterial isolates, which showed very low abundance in IBD, were studied.

RESULTS

Although predominant bacterial diversity was higher in IBD, the numbers of Lachnospiraceae and Coriobacteriaceae bacteria were lower in IBD patients as compared with control children [p < 0.05]. In addition, Ruminococcaceae population diversity was lower in IBD [p < 0.05] and correlated negatively with fecal calprotectin levels. Both abundance and diversity of bifidobacterial populations were lower in children with IBD [p < 0.05], and particularly low numbers of certain bifidobacterial isolates were detected. In CD, we found enhanced up-regulation of interleukin-6 transcripts and impaired RAR-related orphan receptor C response to bifidobacteria, whereas decreased interferon-gamma response was observed in both CD and UC.

CONCLUSION

We demonstrate altered fecal microbiota in paediatric IBD, particularly low numbers and diversity of bifidobacterial populations. Interestingly, immunological response to bifidobacteria differed between paediatric CD patients and control children.

Intestinal microbiota pathogenesis and fecal microbiota transplantation for inflammatory bowel disease

The intestinal microbiota plays an important role in inflammatory bowel disease (IBD). The pathogenesis of IBD involves inappropriate ongoing activation of the mucosal immune system driven by abnormal intestinal microbiota in genetically predisposed individuals. However, there are still no definitive microbial pathogens linked to the onset of IBD. The composition and function of the intestinal microbiota and their metabolites are indeed disturbed in IBD patients. The special alterations of gut microbiota associated with IBD remain to be evaluated. The microbial interactions and host-microbe immune interactions are still not clarified. Limitations of present probiotic products in IBD are mainly due to modest clinical efficacy, few available strains and no standardized administration. Fecal microbiota transplantation (FMT) may restore intestinal microbial homeostasis, and preliminary data have shown the clinical efficacy of FMT on refractory IBD or IBD combined with Clostridium difficile infection. Additionally, synthetic microbiota transplantation with the defined composition of fecal microbiota is also a promising therapeutic approach for IBD. However, FMT-related barriers, including the mechanism of restoring gut microbiota, standardized donor screening, fecal material preparation and administration, and long-term safety should be resolved. The role of intestinal microbiota and FMT in IBD should be further investigated by metagenomic and metatranscriptomic analyses combined with germ-free/human flora-associated animals and chemostat gut models.

Facts, myths and hypotheses on the zoonotic nature of Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of paratuberculosis (Johne's disease [JD]), a chronic granulomatous enteritis in ruminants. JD is one of the most widespread bacterial diseases of domestic animals with significant economic impact. The histopathological picture of JD resembles that of Crohn's disease (CD), a human chronic inflammatory bowel disease of still unresolved aetiology. An aetiological relevance of MAP for CD has been proposed. This and the ambiguity of other published epidemiological findings raise the question whether MAP represents a zoonotic agent. In this review, we will discuss evidence that MAP has zoonotic capacity.

Possible role of Escherichia coli in propagation and perpetuation of chronic inflammation in ulcerative colitis

Background

This study investigated a possible role of Escherichia coli in propagation and perpetuation of the chronic inflammation in ulcerative colitis (UC). The lesions of UC are located superficially on the rectal and/or colonic mucosa. It is suggested that the commensal bacteria of the digestive tract may play a role in the pathogenesis of UC. Several studies have demonstrated proliferation of E. coli in the gut of UC patients. An increase in the number of E. coli in the inflamed tissue is most probably related to the abundance of iron ions produced by the bacteria.

Methods

Colon mucosal biopsies were collected from 30 patients with acute-phase UC, both from tissues with inflammatory changes (n = 30) and unchanged tissue with no inflammatory changes (n = 30) from the same patient. Biopsies were also taken from 16 patients with irritable bowel syndrome diarrhea who comprised the control group. Quantitative and qualitative analysis of the biopsy specimens was performed using culture methods and real-time polymerase chain reaction (PCR). Genotyping of the E. coli isolates was done using pulsed-field gel electrophoresis. Multiplex PCR was used to compare the E. coli strains for the presence of genes responsible for synthesis of iron acquisition proteins: iroN, iutA, iha, ireA, chuA, and hlyA.

Results

We demonstrated that there was a significant increase in the number of E. coli at the sites of inflammation in patients with UC compared to the control group (P = 0.031). Comparative analysis of the restriction patterns of E. coli isolated from inflammatory and unchanged tissues showed that the local inflammatory changes did not promote specific E. coli strains. There was a significant difference in the frequency of the iroN gene in E. coli isolated from patients with UC as compared to the control group.

Conclusions

The increase in the numbers of E. coli in the inflammatory tissues is related to the presence of chuA and iutA genes, which facilitate iron acquisition during chronic intestinal inflammatory processes.

Recent research on bovine paratuberculosis in South Korea

Bovine paratuberculosis (Johne's disease), a chronic and debilitating disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP), is a major cause of chronic ruminant enteritis. A national eradication program has been in place in South Korea since the first report of the disease in 1967; however, only limited data on bovine paratuberculosis in South Korea are available. Some research, such as investigations of the reactivity of animal sera against MAP antigens, has been done in localized areas and in limited animal species. Compared with the worldwide situation, the development of diagnostic methods in South Korea has shown similar results even though some data were obtained from international collaborative studies. MAP is considered by some to be zoonotic, noting an association with Crohn's disease, although this issue is still controversial; however, research into this association is limited. Decisions based on disease priorities have hampered active progress in research on the disease. In this paper, we reviewed the available results generated from South Korea compared with global research. Finally, we propose a theme for future research.

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.

Alternative medicines as emerging therapies for inflammatory bowel diseases

Inflammatory bowel disease (IBD) can be divided into two major categories, ulcerative colitis (UC) and Crohn disease (CD). While the main cause(s) of IBD remain unknown, a number of interventional and preventive strategies have been proposed for use against CD and UC. Many reports have focused on the use of alternative natural medicines as potential therapeutic interventions in IBD patients with minimal side effects. While the use of alternative medicines may be effective in IBD patients that are refractory to corticosteroids or thiopurins, alternative treatment strategies are limited and require extensive clinical testing before being optimized for use in patients.

[Gut microbiota and IBD]

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

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.

Debugging the intestinal microbiota in IBD

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

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.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

[Inflammatory bowel diseases and enteric microbiota]

Intestinal mucosal layers are colonized by a complex microbiota that provides beneficial effects under normal physiological conditions, but is capable of contributing to chronic inflammatory disease such as inflammatory bowel disease (IBD) in susceptible individuals. Studies have shown that the enteric microbiota may drive the development of the gut immune system and can induce immune homeostasis as well as contribute to the development of IBD although the precise etiology is still unknown. Therefore, intestinal microbes seem to play a key role in the disease pathogenesis. Especially, dysbiosis, which is a shift in the composition of enteric microbiota to a nonphysiologic composition, is associated with one or more defects in mucosal immune functions, including microbe recognition, barrier function, intercellular communication, and anti-microbial effector mechanisms. This review focuses on the impact of enteric microbiota on the development and perpetuation of IBD. In addition, interactions with enteric bacteria and mucosal cells, including intestinal epithelial cells, dendritic cells, and T cells, to induce immune responses at mucosal surfaces have been discussed in the point of IBD pathogenesis. Further extension of the knowledge of enteric microbiota may lead to insights on the pathogenesis and new therapeutic strategies for IBD.

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

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

A biosensor assay for the detection of Mycobacterium avium subsp. paratuberculosis in fecal samples

A simple, membrane-strip-based lateral-flow (LF) biosensor assay and a high-throughput microtiter plate assay have been combined with a reverse transcriptase polymerase chain reaction (RT-PCR) for the detection of a small number (ten) of viable Mycobacterium (M.) avium subsp. paratuberculosis (MAP) cells in fecal samples. The assays are based on the identification of the RNA of the IS900 element of MAP. For the assay, RNA was extracted from fecal samples spiked with a known quantity of (10¹ to 10⁶) MAP cells and amplified using RT-PCR and identified by the LF biosensor and the microtiter plate assay. While the LF biosensor assay requires only 30 min of assay time, the overall process took 10 h for the detection of 10 viable cells. The assays are based on an oligonucleotide sandwich hybridization assay format and use either a membrane flow through system with an immobilized DNA probe that hybridizes with the target sequence or a microtiter plate well. Signal amplification is provided when the target sequence hybridizes to a second DNA probe that has been coupled to liposomes encapsulating the dye, sulforhodamine B. The dye in the liposomes provides a signal that can be read visually, quantified with a hand-held reflectometer, or with a fluorescence reader. Specificity analysis of the assays revealed no cross reactivity with other mycobacteria, such as M. avium complex, M. ulcerans, M. marium, M. kansasii, M. abscessus, M. asiaticum, M. phlei, M. fortuitum, M. scrofulaceum, M. intracellulare, M. smegmatis, and M. bovis. The overall assay for the detection of live MAP organisms is comparatively less expensive and quick, especially in comparison to standard MAP detection using a culture method requiring 6-8 weeks of incubation time, and is significantly less expensive than real-time PCR.

Intestinal bacteria and inflammatory bowel disease

Crohn's disease (CD) and ulcerative colitis (UC) are the two principal forms of inflammatory bowel disease (IBD). Animal studies show that bacteria are involved in the etiology of IBD, and much is now known about the inflammatory processes associated with CD and UC, as well as the underlying genetic, environmental, and lifestyle issues that can affect an individual's predisposition to these diseases. However, while a number of candidate microorganisms have been put forward as causative factors in IBD, the primary etiologic agents are unknown. This review discusses the potential role of luminal and mucosal microbial communities in the etiology of IBD, and outlines studies that have been made using a variety of biotherapeutic therapies, involving the use of antibiotics, probiotics, prebiotics, and synbiotics.

Where are all the Mycobacterium avium subspecies paratuberculosis in patients with Crohn's disease?

Mycobacterium avium subspecies paratuberculosis (MAP) causes a chronic granulomatous inflammation of the intestines, Johne's disease, in dairy cows and every other species of mammal in which it has been identified. MAP has been identified in the mucosal layer and deeper bowel wall in patients with Crohn's disease by methods other than light microscopy, and by direct visualization in small numbers by light microscopy. MAP has not been accepted as the cause of Crohn's disease in part because it has not been seen under the microscope in large numbers in the intestines of patients with Crohn's disease. An analysis of the literature on the pathology of Crohn's disease and on possible MAP infection in Crohn's patients suggests that MAP might directly infect endothelial cells and adipocytes and cause them to proliferate, causing focal obstruction within already existing vessels (including granuloma formation), the development of new vessels (neoangiogenesis and lymphangiogenesis), and the "creeping fat" of the mesentery that is unique in human pathology to Crohn's disease but also occurs in bovine Johne's disease. Large numbers of MAP might therefore be found in the mesentery attached to segments of intestine affected by Crohn's disease rather than in the bowel wall, the blood and lymphatic vessels running through the mesentery, or the mesenteric fat itself. The walls of fistulas might result from the neoangiogenesis or lymphangiogenesis that occurs in the bowel wall in Crohn's disease and therefore are also possible sites of large numbers of MAP. The direct visualization of large numbers of MAP organisms in the tissues of patients with Crohn's disease will help establish that MAP causes Crohn's disease.

Review paper: modulation of mononuclear phagocyte function by Mycobacterium avium subsp. paratuberculosis

Pathogenic mycobacteria are highly adapted for survival within host mononuclear phagocytes. This is largely due to the organism's capacity to prevent macrophage activation, block phagosome acidification and maturation, and attenuate presentation of antigens to the immune system. Mycobacterium avium subsp. paratuberculosis (MAP) is one such organism that modulates the ruminant innate immune response. It is the causative agent in paratuberculosis, a chronic progressive granulomatous enteritis in ruminants. MAP initially interacts with cell membrane receptors on bovine mononuclear phagocytes and initiates cell signaling responses and phagocytosis. Mannosylated liparabinomannan (Man-LAM) is a major component of the MAP cell wall that interacts with the cell membrane of mononuclear phagocytes and may be a major virulence factor. Toll-like receptor 2 (TLR2) has been incriminated as major signaling receptor that binds to MAP and initiates signaling though the mitogen-activated protein kinase (MAPK)-p38 pathway. This pathway induces transcription of interleukin (IL)-10. Early production of IL-10 suppresses proinflammatory cytokines, chemokines, IL-12, and major histocompatability factor class-II expression. Both IL-10 dependent and IL-10 independent mechanisms appear to be involved in attenuation of phagosome acidification and phagolysosome fusion. Many of the suppressive effects of MAP on bovine mononuclear phagocytes can be reproduced by exposure of bovine monocytes to Man-LAM. Therefore, MAP Man-LAM-induced TLR2-MAPK-p38 signaling with resultant excessive IL-10 expression has emerged as one of the mechanisms by which MAP organisms suppress inflammatory, immune, and antimicrobial responses and promote their survival within host mononuclear phagocytes.

Mycobacterium avium subspecies paratuberculosis and Crohn's disease granulomas

OBJECTIVE

Chronic infection with Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) has been proposed as a cause of Crohn's disease. Although numerous investigators have examined the link between M. paratuberculosis and Crohn's disease, the evidence remains controversial. The aim of this study was to examine intestinal granuloma from Crohn's patients for M. paratuberculosis using a semi-nested M. paratuberculosis-specific IS900 polymerase chain reaction (PCR).

MATERIAL AND METHODS

Paraffin-embedded ileal or colonic tissues of patients with Crohn's disease were analyzed. Microdissection of this tissue into "granulomas" and "not granulomas" was performed. On the basis of sequences reported in GenBank alignments, we designed primer sets specific for M. paratuberculosis. The presence of the M. paratuberculosis was examined by semi-nested IS900-specific PCR with human beta-actin gene as a control for DNA quality.

RESULTS

Biopsies from 20 Crohn's patients were examined. Human beta-actin gene was amplified in all samples. M. paratuberculosis DNA was detected in the microdissected granuloma in 1 (5%) patient with Crohn's disease and in none of the "not granuloma" tissues.

CONCLUSIONS

M. paratuberculosis DNA can rarely be detected within Crohn's granuloma. These results do not support M. paratuberculosis as the primary etiology of Crohn's disease.

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.

Analysis of bacterial bowel communities of IBD patients: what has it revealed?

The bacterial community, in whole or in part, resident in the bowel of humans is considered to fuel the chronic immune inflammatory conditions characteristic of Crohn's disease and ulcerative colitis. Chronic or recurrent pouchitis in ulcerative colitis patients is responsive to antibiotic therapy, indicating that bacteria are the etiological agents. Microbiological investigations of the bacterial communities in stool or of biopsy-associated bacteria have so far failed to reveal conclusively the existence of pathogens or bacterial communities of consistently altered composition in IBD patients relative to control subjects. Confounding factors need to be eliminated from future studies by using better-defined patient populations of newly diagnosed and untreated individuals and by improved sampling procedures.

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

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

Detection of Mycobacterium avium subspecies paratuberculosis from patients with Crohn's disease using nucleic acid-based techniques: a systematic review and meta-analysis

This study is a systematic review and meta-analysis of studies using nucleic acid-based techniques to detect Mycobacterium avium paratuberculosis (MAP) in patients with Crohn's disease (CD) compared with controls. Database searches were conducted and risk difference estimates were calculated using meta-analysis. Fifty-eight studies were reviewed, 47 of which were included in the analysis. The pooled estimate of risk difference from all studies was 0.23 (95% confidence interval [CI], 0.14-0.32) using a random effects model. Similarly, MAP was detected more frequently from patients with CD compared with those with ulcerative colitis (risk difference 0.19, 95% CI, 0.10-0.28). Year of study, assay type, and inclusion of children explained some but not all of the observed heterogeneity. The data confirms the observation that MAP is detected more frequently among CD patients compared with controls. However, the pathogenic role of this bacterium in the gut remains uncertain. Our analysis demonstrates that there is an association between MAP and CD, across many sites, by many investigators, and controlling for a number of factors; however, this association remains controversial and inconclusive. Future studies should determine whether there is a pathogenic role.

Epidemiological evidence for Mycobacterium avium subspecies paratuberculosis as a cause of Crohn's disease

Mycobacterium avium subspecies paratuberculosis is the causative agent of Johne's disease, a chronic enteritis in ruminants including cattle, sheep, goats, and farmed deer. Recently, this bacterium has received an increasingly wide interest because of a rapidly growing body of scientific evidence which suggests that human infection with this microorganism may be causing some, and possibly all, cases of Crohn's disease. Recent studies have shown that a high percentage of people with Crohn's disease are infected with M. avium subsp. paratuberculosis; whether the association of this bacterium and Crohn's disease is causal or coincidental is not known. Crohn's disease is a gastrointestinal disease in humans with similar histopathological findings to those observed in the paucibacillary form of Johne's disease in cattle. The search for risk factors in Crohn's disease has been frustrating. However, epidemiologists have gathered enough information that points to an association between M. avium subsp. paratuberculosis and Crohn's disease. This paper reviews epidemiological models of disease causation, the major philosophical doctrines about causation, the established epidemiological criteria for causation, and the currently known epidemiological evidence of M. avium subsp. paratuberculosis as a possible cause of Crohn's disease.

Mycobacterium avium subspecies paratuberculosis and Crohn's disease: a systematic review and meta-analysis

This systematic review assesses the evidence for an association between Mycobacterium avium subspecies paratuberculosis (MAP) and Crohn's disease. We analysed 28 case-control studies comparing MAP in patients with Crohn's disease with individuals free of inflammatory bowel disease (IBD) or patients with ulcerative colitis. Compared with individuals free of IBD, the pooled odds ratio (OR) from studies using PCR in tissue samples was 7.01 (95% CI 3.95-12.4) and was 1.72 (1.02-2.90) in studies using ELISA in serum. ORs were similar for comparisons with ulcerative colitis patients (PCR, 4.13 [1.57-10.9]; ELISA, 1.88 [1.26-2.81]). The association of MAP with Crohn's disease seems to be specific, but its role in the aetiology of Crohn's disease remains to be defined.

Influence of Mycobacterium avium subsp. paratuberculosis on colitis development and specific immune responses during disease

The granulomatous and intramural inflammation observed in cases of inflammatory bowel diseases (IBD) and veterinary Johne's disease suggests that Mycobacterium avium subsp. paratuberculosis is a causative agent. However, an incomplete understanding of the immunological steps responsible for the pathologies of IBD makes this conclusion uncertain. Sera from interleukin-10-deficient (IL-10(-/-)) mice with spontaneous colitis displayed significantly higher M. avium subsp. paratuberculosis-specific immunoglobulin G2a antibody responses than did sera from similar mice without disease. Pathogen-free IL-10(-/-) mice received control vehicle or the vehicle containing heat-killed or live M. avium subsp. paratuberculosis. Mucosal CD4(+) T cells from the mice that developed colitis proliferated and secreted higher levels of gamma interferon and tumor necrosis factor alpha after ex vivo stimulation with a Vbeta11(+) T-cell receptor-restricted peptide from the MPT59 antigen (Ag85B) than those secreted from cells from mice before the onset of colitis. The data from this study provide important information regarding the mechanisms of colitis in IL-10(-/-) mice, which are driven in part by Ag85B-specific T cells. The data suggest a plausible mechanism of Ag-specific T-cell responses in colitis driven by potent Ags conserved in Mycobacterium species.

Molecular evidence for Mycobacterium avium subspecies paratuberculosis (MAP) in Crohn's disease correlates with enhanced TNF-alpha secretion

BACKGROUND

Support for a role of Mycobacterium avium subspecies paratuberculosis in Crohn's disease is largely based on epidemiological evidence, as no data on mechanisms linking the presence of M. avium subspecies paratuberculosis with gut damage is available.

AIMS

To determine whether the presence of M. avium subspecies paratuberculosis contributes to the pathogenesis of Crohn's disease by promoting cytokine secretion within gut mucosa.

PATIENTS AND METHODS

A total of 235 subjects were recruited: 63 with Crohn's disease, 53 with ulcerative colitis, 45 with irritable bowel syndrome and 74 normal controls. M. avium subspecies paratuberculosis status was defined by nested PCR using IS900 sequence. Gut mucosal organ cultures were established to detect cytokine secretion patterns.

RESULTS

Significantly higher tumour necrosis factor-alpha concentrations were found in culture supernatants for Crohn's disease compared to ulcerative colitis (p<0.05), irritable bowel syndrome (p<0.01) and controls (p<0.0001). When tumour necrosis factor-alpha levels were correlated with the presence of M. avium subspecies paratuberculosis, significantly greater concentrations were only found in M. avium subspecies paratuberculosis-positive Crohn's disease patients (p<0.05). Tumour necrosis factor-alpha levels in M. avium subspecies paratuberculosis-positive Crohn's disease were significantly higher than in M. avium subspecies paratuberculosis-positive ulcerative colitis (p<0.01), M. avium subspecies paratuberculosis-positive irritable bowel syndrome (p<0.05) and M. avium subspecies paratuberculosis-positive controls (p<0.01) and all M. avium subspecies paratuberculosis-negative specimens.

CONCLUSIONS

The data link M. avium subspecies paratuberculosis with a pathogenic mechanism in Crohn's disease and is consistent with abnormal macrophage handling of M. avium subspecies paratuberculosis.

Anti-mycobacterial therapy in Crohn's disease heals mucosa with longitudinal scars

BACKGROUND

A possible causative link between Crohn's disease and Mycobacterium avium ss paratuberculosis has been suggested.

AIM

To report unique scarring in Crohn's disease patients treated with anti-Mycobacterium avium ss paratuberculosis therapy.

PATIENTS

A retrospective review of 52 patients with severe Crohn's disease was conducted. Thirty-nine patients who had at least one follow-up colonoscopy during treatment were included.

METHODS

Patients received rifabutin (up to 600 mg/day), clofazimine (up to 100 mg/day) and clarithromycin (up to 1 g/day) - anti-Mycobacterium avium ss paratuberculosis therapy - for 6 months to 9 years. Ramp-up dosing was used. Colonoscopies and histological analyses monitored progress.

RESULTS

Twenty-two patients (56.4%, 22/39) healed with unusual scarring, which appeared as branched, ribbon-like, elevated lines. In 2/6 patients (33.3%) who had > 3 years of treatment after scarring occurred, scars receded, becoming imperceptible as full healing occurred. Histologically, a marked reduction in inflammation occurred in 15/39 patients (38.5%). Of these, 6/15 patients (40%) displayed restoration of normal mucosa. Longitudinal scarring occurred in 12/15 patients (80%) with improved histology.

CONCLUSIONS

The presence of scarring fading to normal mucosa on anti-MAP therapy implies a more profound healing not seen with standard anti-inflammatory and immunosuppressant drugs. Longitudinal scarring and consequent healing with normal histology should become a standard treatment goal for Crohn's disease.

Mycobacterium avium in the postgenomic era

The past several years have witnessed an upsurge of genomic data pertaining to the Mycobacterium avium complex (MAC). Despite clear advances, problems with the detection of MAC persist, spanning the tests that can be used, samples required for their validation, and the use of appropriate nomenclature. Additionally, the amount of genomic variability documented to date greatly outstrips the functional understanding of epidemiologically different subsets of the organism. In this review, we discuss how postgenomic insights into the MAC have helped to clarify the relationships between MAC organisms, highlighting the distinction between environmental and pathogenic subsets of M. avium. We discuss the availability of various genetic targets for accurate classification of organisms and how these results provide a framework for future studies of MAC variability. The results of postgenomic M. avium study provide optimism that a functional understanding of these organisms will soon emerge, with genomically defined subsets that are epidemiologically distinct and possess different survival mechanisms for their various niches. Although the status quo has largely been to study different M. avium subsets in isolation, it is expected that attention to the similarities and differences between M. avium organisms will provide greater insight into their fundamental differences, including their propensity to cause disease.

Evaluation of in situ methods used to detect Mycobacterium avium subsp. paratuberculosis in samples from patients with Crohn's disease

In common with other diagnostic tests, detection of mycobacteria in tissue by microscopic examination is susceptible to spectrum bias. Since Crohn's disease is defined by the absence of detectable pathogenic organisms, the use of in situ techniques to search for Mycobacterium avium subsp. paratuberculosis in Crohn's disease samples requires validation of methods in a paucibacillary setting. To generate paucibacillary infection, C57BL/6 mice were artificially infected with Mycobacterium avium subsp. paratuberculosis strain K10 and M. tuberculosis H37Rv, yielding tissues harboring fewer than one bacillus per oil immersion field. Serial sections of organs were then studied by cell wall-based staining techniques (Ziehl-Neelsen and auramine rhodamine) and nucleic acid-based staining techniques (in situ hybridization [ISH] and indirect in situ PCR [IS PCR]). Microscopic examination and measurement of morphometric parameters of bacilli revealed that for all methods, Mycobacterium avium subsp. paratuberculosis bacilli were observed to be shorter, smaller, and less rod shaped than M. tuberculosis bacilli. Ziehl-Neelsen, auramine rhodamine stains, ISH targeting rRNA, and IS-PCR targeting the IS900 element afforded comparable sensitivities, but for all methods, visualization of individual bacterial forms required magnification x1,000. Auramine rhodamine staining and IS-PCR generated positive signals in negative controls, indicating the nonspecificity of these assays. Together, our results indicate that detection of Mycobacterium avium subsp. paratuberculosis bacilli in tissue requires oil immersion microscopy, that rRNA-ISH provides sensitivity and specificity comparable to those of Ziehl-Neelsen staining, and that the microscopic detection limit for Mycobacterium avium subsp. paratuberculosis in tissue is governed more by bacterial burden than by staining method.

Comparative transcriptional analysis of human macrophages exposed to animal and human isolates of Mycobacterium avium subspecies paratuberculosis with diverse genotypes

Mycobacterium avium subsp. paratuberculosis is the causative agent of Johne's disease in animals and has been hypothesized to be associated with Crohn's disease in humans. Recently, M. avium subsp. paratuberculosis isolates recovered from Crohn's disease patients were shown to have limited diversity, implying the existence of human disease-associated genotypes and strain sharing with animals (A. H. Ghadiali et al., J. Clin. Microbiol. 42:5345-5348, 2004). To explore whether these genotypic differences or similarities among human and animal isolates translated to functionally significant attributes such as variance in host preference and/or difference in magnitude of infections, we performed a global scale analysis of M. avium subsp. paratuberculosis isolates that were representative of different genotypes and host species using DNA microarrays. Genome-wide characterization of the transcriptional changes was carried out using a human monocytic cell line (THP-1 cells) in response to different genotypes of M. avium subsp. paratuberculosis isolates recovered from various hosts. We identified several differentially expressed genes during early intracellular infection, including those involved in common canonical pathways such as NF-kappaB, interleukin-6 (IL-6), mitogen-activated protein kinase/extracellular signal-regulated kinase, and Jun N-terminal protein kinase signaling, as well as genes involved in T helper type 1 (Th1) responses (such as CCL5 ligand) and those that encode several proinflammatory cytokines and chemokine receptors. The cattle and human isolates of M. avium subsp. paratuberculosis, regardless of their short sequence repeat (SSR) genotype, induced similar global gene expression patterns in THP-1 cells. They differentially regulated genes necessary for cell survival without causing major alterations in proinflammatory genes. In contrast, the sheep isolates representing diverse SSR genotypes closely resembled the global gene expression pattern of an M. avium subsp. avium isolate, and they significantly up-regulated proinflammatory genes related to IL-6, T-cell receptor, B-cell receptor, and death receptor signaling within THP-1 cells. Additionally, we demonstrated consistency among infecting genotypes of M. avium subsp. paratuberculosis isolated from diverse hosts [cattle (n=2), human (n=3), sheep (n=2), and bison (n=1)] in quantitative reverse transcription-PCR analysis of seven differentially expressed genes. While the levels of expression induced by the bison isolate were different compared with cattle or human isolates, they followed the common anti-inflammatory, antiapoptotic trend. Our data suggest that the macrophage responses to M. avium subsp. paratuberculosis isolates from cattle and human sources, regardless of genotype, follow a common theme of anti-inflammatory responses, an attribute likely associated with successful infection and persistence. However, these expression patterns differ significantly from those in THP-1 cells infected with sheep isolates of M. avium subsp. paratuberculosis or the M. avium subsp. avium isolate. These data provide a transcriptional basis for a variety of pathophysiological changes observed during early stages of infection by different strains of M. avium subsp. paratuberculosis, a first step in understanding trait-allele association in this economically important disease.

Evaluation of peptide nucleic acid-fluorescence in situ hybridization for identification of clinically relevant mycobacteria in clinical specimens and tissue sections

With fluorescently labeled PNA (peptide nucleic acid) probes targeting 16S rRNA, we established a 3-h fluorescence in situ hybridization (FISH) procedure for specific visualization of members of the Mycobacterium tuberculosis complex, M. leprae, M. avium, and M. kansasii. Probe specificity was tested against a panel of 25 Mycobacterium spp. and 10 gram-positive organisms. After validation, probes were used to identify 52 mycobacterial culture isolates. Results were compared to conventional genotypic identification with amplification-based methods. All isolates (M. tuberculosis complex, n = 24; M. avium, n = 7; M. kansasii, n = 1) were correctly identified by FISH. In addition, the technique was used successfully for visualization of mycobacteria in biopsies from infected humans or animals. In conclusion, PNA-FISH is a fast and accurate tool for species-specific identification of culture-grown mycobacteria and for direct visualization of these organisms in tissue sections. It may be used successfully for both research and clinical microbiology.

Current concept on the pathogenesis of inflammatory bowel disease-crosstalk between genetic and microbial factors: Pathogenic bacteria and altered bacterial sensing or changes in mucosal integrity take “toll”

The pathogenesis of inflammatory bowel disease (IBD) is only partially understood. Various environmental and host (e.g. genetic-, epithelial-, immune and non-immune) factors are involved. It is a multifactorial polygenic disease with probable genetic heterogeneity. Some genes are associated with IBD itself, while others increase the risk of ulcerative colitis (UC) or Crohn’s disease (CD) or are associated with disease location and/or behaviour. This review addresses recent advances in the genetics of IBD. The article discusses the current information on the crosstalk between microbial and genetic factors (e.g. NOD2/CARD15, SLC22A46A5 and DLG5). The genetic data acquired in recent years help in understanding the pathogenesis of IBD and can identify a number of potential targets for therapeutic intervention. In the future, genetics may help more accurately diagnose and predict disease course in IBD.

Specific antibodies against recombinant protein of insertion element 900 of Mycobacterium avium subspecies paratuberculosis in Japanese patients with Crohn's disease

BACKGROUND

Mycobacterial avium subspecies paratuberculosis (MAP) infection has been hypothesized as an etiological factor of Crohn's disease (CD). However, the involvement of MAP in the pathophysiology of CD is controversial. The aim of this study is to investigate whether MAP is involved in the pathogenesis of CD with the glutathione S-transferase fusion recombinant protein encoding a portion of insertion element (IS) 900 (IS900-GST), which is specific for MAP.

METHODS

Serum samples from the patients with CD (n = 50), ulcerative colitis (n = 40), colonic tuberculosis (n = 20), and non-IBD controls (n = 44), were applied for solid-phase enzyme-linked immunosorbent assay (ELISA) to detect antibodies against MAP and Saccharomyces cerevisiae. IS900-GST, which was made by the pGST-4T-2 vector inserted with polymerase chain reaction-amplified IS900DNA, was used as an antigen of MAP. Moreover, we studied the relationship between antibodies against IS900-GST and clinical characteristics.

RESULTS

ELISA showed that the serum level of immunoglobulin G and immunoglobulin A antibodies against IS900-GST (anti-IS900) in patients with CD were significantly higher than those with ulcerative colitis, colonic tuberculosis, and control subjects. The levels of anti-IS900 tended to be higher in CD patients with small intestinal involvement than with colonic involvement alone. Anti-IS900 in patients with penetrating- and stricture-type CD was significantly higher than with inflammatory-type CD. Furthermore, a negative correlation was found between the titer of anti-IS900 and disease duration. Anti-IS900 was not associated with surgical treatment nor was it associated with the use of immunosuppressants. No significant correlation was observed between the serum levels of anti-IS900 and anti-S cerevisiae antibody.

CONCLUSIONS

This is the first demonstration of the ELISA system of detecting antibodies against IS900 in IBD patients. MAP could be involved in the pathophysiology of Japanese patients with CD.

Real-time quantitative PCR detection of Mycobacterium avium subsp. paratuberculosis and differentiation from other mycobacteria using SYBR Green and TaqMan assays

Sensitive real-time sequence detection methods based on two different chemistries were developed for Mycobacterium avium subsp. paratuberculosis (Map), the causative agent of Johne's disease in cattle. One is based on the detection of SYBR Green bound to PCR products and the second method is more specific, detecting the cleavage of a fluorogenic (TaqMan) probe bound to a target sequence during primer extension phase. Novel primers and probes that amplify small fragments (<80 bp) of the Map specific insertion sequence, IS900 were designed. Both the SYBR Green and TaqMan assays are sensitive, able to detect 4 fg of DNA extracted from Map strain ATCC19698. This amount of DNA corresponds to the detection of 0.8 cells. Map cells were quantified directly from 7H9 broth using the SYBR Green assay and compared to dilutions of DNA extracted from an equivalent number of cells. The SYBR Green assay of 7H9 broth resulted in a minimum detectable limit of 0.07 cells (equivalent to 0.34 fg of DNA). Media ingredients were not observed to interfere with the assay. Since no extraction step was necessary in the direct cell measurements, direct detection was ten-fold more sensitive than detection of extracted DNA. Both SYBR Green and TaqMan assays are highly specific for the detection of Map. They did not detect any closely related members of the avium complex, other species of mycobacteria, or related genera that are likely to be present in environmental samples. No reporter signal was detected during TaqMan assays performed with 100 pg of template DNA from the non-Map organisms.

Detection of Mycobacterium avium subspecies paratuberculosis in Swiss dairy cattle by real-time PCR and culture: a comparison of the two assays

AIMS

To compare the two different diagnostic assays for the detection of Mycobacterium avium ssp. paratuberculosis, the aetiological agent of paratuberculosis.

METHODS AND RESULTS

Faecal samples were derived from 310 cows, representing 13 commercial dairy herds in various locations in Switzerland with expected increased risk because of a past history of disease. Detection assays for M. avium ssp. paratuberculosis were culture (gold standard) and a newly designed real-time PCR. Real-time PCR identified 31 of 310 animals as positive within this risk population whereas culture identified 20 positive animals. The specificity of real-time PCR was confirmed by DNA sequencing of the PCR product. Depending on the test used, the paratuberculosis prevalence in our tested risk population ranged from 6.5 to 10%.

CONCLUSIONS

Real-time PCR and culture data were in good agreement, and real-time PCR generates data in a short time in contrast to culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

We consider real-time PCR as a suitable alternative method to culture for the detection of M. avium ssp. paratuberculosis in a national surveillance programme.

Detection of Mycobacterium avium subsp. paratuberculosis in intestinal and lymph node tissues of water buffaloes (Bubalus bubalis) by PCR and bacterial culture

The efficacy of bacterial culture and IS900-specific polymerase chain reaction (PCR) was compared for the detection of Mycobacterium avium subsp. paratuberculosis (MAP) from the intestinal and mesenteric lymph node tissues of water buffaloes (Bubalus bubalis) showing lesions of paratuberculosis (Johne's disease). Out of 20 (4.9%) animals showing histological lesions suggestive of paratuberculosis, 14 (70%) and 6 (30%) were positive in the PCR and bacterial culture, respectively. The results of this study suggested that PCR was more sensitive than bacterial culture in detection of subclinical paratuberculosis in water buffaloes. The bacterial concentration from large amount of tissues by differential and density gradient centrifugation method was found to facilitate the diagnosis by smear examination and PCR. The specificity of the PCR was confirmed by the product size and restriction digestion pattern of the amplicons. The sequence analysis of the amplified products (626bp of IS900 gene) from buffalo strain showed more than 97% homology with the published sequences.

Use of specific rRNA oligonucleotide probes for microscopic detection of Mycobacterium avium complex organisms in tissue

Members of the Mycobacterium avium complex (MAC) are important environmental pathogens that are implicated in several chronic, idiopathic diseases. Diagnosis of MAC-based diseases is compromised by the need to cultivate these fastidious and slowly growing organisms in order to identify which mycobacterial species are present. Detection is particularly difficult when MAC is intracellular or embedded within mammalian tissues. We report on the development of culture-independent, in situ hybridization (ISH) assays for the detection of MAC in culture, sputum, and tissue. This assay includes a highly reliable technique for the permeabilization of mycobacterial cells within culture and tissues. We describe a set of rRNA-based oligonucleotide probes that specifically detect either M. intracellulare, the two M. avium subspecies associated with human disease, or all members of MAC. The results call into question the validity of ISH results derived by the use of other gene loci, such as IS900.

A critical role of interleukin-10 in the response of bovine macrophages to infection by Mycobacterium avium subsp paratuberculosis

OBJECTIVES

To evaluate the role of interleukin (IL)-10 in the inability of monocyte-derived bovine macrophages to kill Mycobacterium avium subsp paratuberculosis organisms in vitro.

SAMPLE POPULATION

Monocytes were obtained from healthy adult Holstein dairy cows that had negative results when tested for infection with M avium subsp paratuberculosis.

PROCEDURE

Monocyte-derived macrophages were incubated with M avium subsp paratuberculosis for 2, 6, 24, 72, or 96 hours with or without addition of saturating concentrations of a goat anti-human IL-10 that has been documented to neutralize bovine IL-10 activity. Variables assessed included ingestion and killing of M avium subsp paratuberculosis; expression of tumor necrosis factor (TNF)-alpha, IL-12, IL-8, major histocompatability (MHC) class II, vacuolar H+ ATPase, and B cell CLL/lymphoma 2 (BCL-2); production of nitric oxide; acidification of phagosomes; and apoptosis of macrophages.

RESULTS

Neutralization of IL-10 enabled macrophages to kill 57% of M avium subsp paratuberculosis organisms within 96 hours. It also resulted in an increase in expression of TNF-alpha, IL-12, IL-8, MHC class II, and vacuolar H+ ATPase; decrease in expression of BCL-2; increase in acidification of phagosomes; apoptosis of macrophages; and production of nitric oxide.

CONCLUSIONS AND CLINICAL RELEVANCE

The capacity of M avium subsp paratuberculosis to induce IL-10 expression may be a major determinant of virulence for this organism.