Identification of Mycobacterium avium Genotypes with Distinctive Traits by Combination of IS 1245 -Based Restriction Fragment Length Polymorphism and Restriction Analysis of hsp65

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Abstract
One-hundred eight Mycobacterium avium isolates from pigs, humans, birds, and bovines were typed by the IS 1245 -based restriction fragment length polymorphism (RFLP) method and PCR-restriction enzyme analysis (PRA) of hsp65 . Nine clusters of isolates showing more than 80% similarity in their RFLP profiles were detected. The largest cluster (cluster B) included 32 of 79 pig isolates (40.5%), 3 of 25 human isolates (12%), and 1 of 2 bovine isolates, comprising 33% of all isolates. The second largest cluster (cluster A) included 18 pig isolates (22.8%) and 6 human isolates (24%). Six smaller clusters included six pig isolates (clusters C and D), four and two human isolates (clusters E and F, respectively), two pig isolates (cluster I), and two pig isolates plus one bovine isolate and the avian purified protein derivative strain (cluster H). Cluster G represented the “bird-type” profile and included the bird isolate in this series, one pig isolate, plus reference strain R13. PRA revealed four allelic variants. Seventy-seven isolates were identified as M. avium PRA variant I, 24 were identified as M. avium PRA variant II, 6 were identified as M. avium PRA variant III, and 1 was identified as M. avium PRA variant IV. Except for three isolates from cluster B, each of the RFLP clusters was associated with a single PRA pattern. Isolates with unique (nonclustered) RFLP profiles were distributed between PRA variants I and II, and there was one unique isolate of PRA variant IV. These observations are consistent with divergent evolution within M. avium , resulting in the emergence of distinct lineages with particular competence to infect animals and humans.

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