Mycobacterium paratuberculosis and Mycobacterium avium subsp. silvaticum DNA cannot be detected by PCR in Crohn's disease tissue.
BACKGROUND: The etiology of Crohn's disease remains unknown. A putative mycobacterial cause of the disease is still controversial. AIMS: To assess the mycobacterial hypothesis in Crohn's disease using a polymerase chain reaction technique. PATIENTS AND METHODS: Nested polymerase chain reaction with primers on the 16S-rRNA coding region (16S-rDNA) and with primers specific both to the insertion sequences (IS) 900, and IS 901/902 were used to amplify Mycobacterium paratuberculosis or Mycobacterium avium subsp. silvaticum DNA in frozen endoscopic intestinal biopsies or surgical resection specimens from patients with Crohn's disease (n = 47: 25 endoscopic biopsies and 22 surgical resection samples, +/- lymph nodes), ulcerative colitis (n = 27), and non inflammatory bowel diseases (n = 20: colonic tumors and diverticulitis). Positive as well as negative controls were used throughout the study. RESULTS: All strains of Mycobacterium paratuberculosis and Mycobacterium avium subsp. silvaticum tested were positive for both primer systems. Of the 94 biopsies tested, 5 (2 Crohn's disease, 1 ulcerative colitis and 2 controls) were positive with the 16S-rDNA primers but did not correspond to Mycobacterium paratuberculosis or Mycobacterium avium subsp. silvaticum. None of the specimens was positive with the IS primers. CONCLUSION: These results do not support the hypothesis that Mycobacterium paratuberculosis, or Mycobacterium avium subsp. silvaticum play a role in Crohn's disease.