Mycobacterium avium subsp. paratuberculosis and M. avium subsp. avium are closely related, but cause different disease complexes. Distribution of various IS elements have been used for diagnosis and strain typing of these species. Our objective was to investigate the distribution of ISMpa1, IS1245 and IS1311 in the two subspecies by PCR and Restriction Fragment Length Polymorphism (RFLP).PCR analysis showed that all examined strains of M. a. paratuberculosis harboured ISMpa1, and an identical pattern was demonstrated inn all isolates with ISMpa1-RFLP. Among the M. a. avium strains, only a few isolates harboured ISMpa1, and the ISMpa1-RFLP revealed a different pattern from the M. a. paratuberculosis isolates. These findings suggest that M. a. avium have acquired the element at a later evolutionary stage.IS1245 and IS1311 share a 85 % DNA sequence homology. IS1245-RFLP of M. a. avium has been performed by a standardised method, where weak and inconsistent bands have made analysis difficult. There has also been some discrepancy in the literature about the presence of IS1245 in M. a. paratuberculosis. Cross hybridisation is a possible explanation for these findings. We designed shorter and more specific probes for the two elements. Performing IS1245-RFLP on M. a. paratuberculosis isolates gave no hybridisation signals, but with IS1311-RFLP an identical seven-banded pattern was revealed in all strains. These results show that IS1245 is not a part of the genome of M. a. paratuberculosis. Isolates of M. a. avium from humans and swine showed multibanded patterns with both probes, with easier interpretable patterns than with the standardised IS1245-RFLP. It is well recognised that M. a. avium isolates from birds show an identical three banded pattern described as the "bird-type" pattern with the standardised IS1245-RFLP. It was demonstrated that this pattern actually consisted of two copies of IS1311 and one copy of IS1245.

Sponsorship

²Attendance to this Congress was sponsored by the EU-funded project SSPE-CT-2004-501903