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 printers 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 ol 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
Ail 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.