MYCOBACTERIA OF RUNYON GROUP-I, GROUP-II AND GROUP-IV DO NOT PLAY AN ETIOLOGIC ROLE IN CROHNS-DISEASE

Objective: In addition to Mycobacterium paratuberculosis, other slow-g rowing as well as rapid-growing mycobacteria were isolated from mucosa or full thickness samples of intestine from patients with Crohn's dis ease. The meaning of these data remained unclear. To investigate the p ossible aetiological role of these rapid- and slow-growing mycobacteri a, serosa and mesenteric lymph nodes were also cultivated in the prese nt study. Design and methods: Mucosa, lymph nodes and serosa of 23 pat ients with Crohn's disease and 23 patients with other intestinal affli ctions were incubated at 37 degrees C on Lowenstein-Jensen medium and Herrold egg yolk medium. These methods allow the cultivation of most a typical mycobacteria, including Mycobacterium paratuberculosis. In add ition, full thickness samples of some of these patients were analysed for mycobacterial DNA using polymerase chain reaction. Results: Despit e lack of decontamination of 60% of lymph nodes and serosa, no mycobac terial growth was observed over a long incubation period (an average o f 718 days in Crohn's disease and 552 days in controls) on Lowenstein- Jensen medium. Polymerase chain reaction was based on the amplificatio n of 16S ribosomal DNA sequences specific for mycobacteria of tissues derived from four patients with Crohn's disease and one control was ne gative. Conclusions: These findings suggest that mycobacteria, such as M. fortuitum and M. chelonei, which are widespread in the environment , are not involved in the aetiology of Crohn's disease but, rather, sh ould be considered as environmental opportunists.