Objective: To assess the frequency of Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) in patients with M. Crohn (MC) in the Czech Republic. Patients and examination methods: In 49 patients with a clinically and histologically confirmed diagnosis of MC from the pathological tissue collected during resection of the gut cultivation focused on M. paratuberculo- sis was implemented. In suitable patients also cultivation from the non-affected portions of the gut was made. Before bacteriological examination, the tissue obtained during surgery was frozen to -40 °C. The tissue was then homogenized and the inoculum was cultivated on Herold’s medium with a growth stimulator Mycobactin J. The isolated strains were identified by the PCR method (detection of the specific fragment IS900 for M. paratuberculosis) and for more detailed detection the RFLP method (Restriction Fragment Length Polymor- phisms) was used. Results: In three patients, in all from pathologically altered tissue M. paratuberculosis was obtained by cultivation of RFLP types A-C10, D-C12 and B-C1. All these three RFLP types of strains are found also in cattle and other ruminants in the Czech Republic. Conclusions: Evidence of M. paratuberculosis by cultivation in three of 49 patients with MC in pathologically altered intestinal tissue (contrary to negative results from normal tissue) supports reflections on the partici- pation of M. paratuberculosis in the etiopathogenesis of MC. It is consistent with experience published in western countries. The low detection rate of M. paratuberculosis can be explained by the difficult cultivation of this microorganism and some of its other properties.

        Key words: M. Crohn – Mycobacterium avium subsp. paratuberculosis – Johne’s disease – paratuberculosis