USE OF MULTILOCUS ENZYME ELECTROPHORESIS TO EXAMINE GENETIC-RELATIONSHIPS AMONGST ISOLATES OF MYCOBACTERIUM-INTRACELLULARE AND RELATED SPECIES

As part of a larger study investigating diversity and distribution of Mycobacteium spp. in Australia, multilocus enzyme electrophoresis was used to assess genetic relationships at 17 enzyme loci amongst a colle ction of reference strains and grounds as M. intracellulare (70),'X' m ycobacteria (10), M. scrofulaceum (7), Laboratory for Bovine M. avium (8) and M. avium subsp. paratuberculosis (2). Two of the isolates init ially identified as M. intracellulare were shown to be quite distinct from the others. Both gave negative results in a species-specific DNA probe test, whilst one was positive by PCR. These results emphasize th e uncertainties involved in identifying members of this group. The oth er M. intracellulare isolates formed a cohesive but diverse group, bei ng divided into 48 electrophoretic types (ETs), with a mean genetic di versity of 0.38. Forty-three of these ETs contained only single isolat es. There was no clear relationship between the serovar and ET designa tion. The index of association calculated for M. intracellulare was si gnificantly different from zero, suggesting that it is a clonal specie s. PFGE was also applied to selected isolates from the ETs containing multiple isolates, and some of these could be differentiated further. The strains of M. scrofulaceum and 'X' mycobacteria were distinct from M. intracellulare, but themselves were highly heterogeneous, with mea n genetic diversities of 0.66 and 0.65, respectively. Each of these gr oups may represent more than one species. M. avium strains were distin ct from the two M. avium subsp. paratuberculosis strains, as well as f rom the other mycobacteria studied.