Results of Multiple Diagnostic Tests forMycobacterium aviumsubsp.paratuberculosisin Patients with Inflammatory Bowel Disease and in Controls

Abstract

Mycobacterium avium subsp. paratuberculosishas been incriminated as a cause of Crohn's disease (CD); however, studies to date have been relatively small and generally only used a single diagnostic assay. The objective of the study was to reexamine the association of M. avium subsp.paratuberculosis and CD using multiple diagnostic tests. Five methods were used to detect M. avium subsp.paratuberculosis infections in 439 inflammatory bowel disease (IBD) patients and 324 control subjects in the United States and Denmark. Most assays were adaptations of diagnostic tests for this infection performed routinely on animals. PCR for IS900, a genetic element unique to M. avium subsp.paratuberculosis, was positive significantly more often on resected bowel and lymph node tissues from CD patients (19.0%) and ulcerative colitis (UC) patients (26.2%) than from controls (6.3%) (P < 0.05). Positive IS900 PCR results occurred more often in U.S. than in Danish IBD patients, 32.0 versus 13.3% (P = 0.025). The majority of Danish patients were bacillus Calmette-Guérin (Mycobacterium bovisBCG) vaccinated (CD, 77.5%; UC, 86.6%; controls, 83.0%) whereas none of the U.S. patients with IBD and only 2% of U.S. controls were vaccinated. Among Danish IBD patients, positive PCR findings were four times more common among subjects who were not BCG vaccinated (33.3%) than among BCG vaccinates (8.8%, P = 0.02). Culture of the same tissues tested by PCR using modified BACTEC 12B medium failed to grow M. avium subsp. paratuberculosisfrom patients or controls. U.S. CD patients had the highest serological evidence (enzyme-linked immunosorbent assay [ELISA] for serum antibodies) of M. avium subsp. paratuberculosisinfection (20.7% of patients positive) which was higher than for all UC patients studied (6.1%) or healthy controls (3.8%,P < 0.005). Among Danish patients alone, however, no significant differences in rates of ELISA-positive results among CD, UC, or control patients were found. For 181 study subjects, both IS900 PCR and ELISA were performed. Although 11 were ELISA positive and 36 were PCR positive, in no instance was a patient positive by both tests, suggesting that these states are mutually exclusive. Evaluation of cytokine-mediated immune responses of IBD patients was complicated by the influence of immunosuppressive therapy given most IBD patients. Gamma interferon (IFN-γ) release by peripheral blood leukocytes after M. avium purified protein derivative PPD antigen stimulation showed significantly lower responses in CD patients than in UC patients or controls in both U.S. (by ex vivo assay) and Danish (by in vitro assay) populations (P< 0.05). Interleukin-5 responses were not different among CD, UC, or control groups. Collectively, the PCR, ELISA, and IFN-γ tests forM. avium subsp. paratuberculosis together with the unexpected observation that BCG vaccination influenced M. avium subsp. paratuberculosis detection, lead us to conclude that M. avium subsp. paratuberculosis, or some similarly fastidious mycobacterial species, infects at least a subset of IBD patients. Whether the infection is primary (causal) or secondary, it may contribute to the etiopathogenesis of IBD.

Presence and characterization of Mycobacterium avium subspecies paratuberculosis from clinical and suspected cases of Crohn's disease and in the healthy human population in India

“…Similar high prevalence of MAP has been reported in Crohn's disease patients and controls by other workers. 13,17,40,41 Sensitivities of culture and ELISA were similar for the detection of MAP in humans. Sanderson et al 42 reported that culture was less sensitive as compared to PCR.…”

“…52,53 Though Hermon-Taylor reported 28 different strains of MAP and some specific to particular species like sheep and cattle, 12 in North India, MAP 'bison type' was the most prevalent genotype in animals. 52,53 Collins et al 40 detected MAP in significantly higher numbers of patients with Crohn's disease than in controls. Similarly in this study, all the Crohn's disease patients were positive by ELISA as compared to 80.0% by culture.…”

Zoonotic potential ofMycobacterium aviumssp.paratuberculosis: the current position

“…However, the same ELISA method had been used by Collins et al. (2000) to test sera from Crohns’ disease and control subjects from the USA and Denmark and in that study a much higher percentage of Crohn's patients tested positive for Map by ELISA (20·7% Crohn's compared with 3·8% healthy controls).…”

Detection of Mycobacterium Avium Subsp. Paratuberculosis in Bovine Fecal Samples: Comparison of Three Polymerase Chain Reaction—Based Diagnostic Tests with a Conventional Culture Method

“…Interest in the disease is growing, not only because of the vast economic losses for farmers but also because of the hypothesized involvement of MAP in the etiology of Crohn disease. 2,3,6,10,12,22,28 Mycobacterium avium subsp. paratuberculosis is an intracellular pathogen that replicates in macrophages in the lamina propria and is shed into the feces during disease.…”