Characterization of clinical isolates of Mycobacterium paratuberculosis by DNA-DNA hybridization and cellular fatty acid analysis.

The DNA-DNA homologies obtained were more than 90 per cent for all strains examined, including the reference strains of Mycobacterium paratuberculosis and Mycobacterium avium. Consequently, in a genetic sense, M. paratuberculosis with its variants belong to a single species which should be considered a subspecies of M. avium. The same reference strains of M. paratuberculosis and M. avium showed small but distinct differences in the cellular fatty acid patterns. The Norwegian goat isolate proved to be M. paratuberculosis, while the three sheep isolates from Iceland and the Faroe Islands showed a typical M. avium pattern.