Taxonomic Studies on the Mycobacterium tuberculosis Series

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Abstract
Numerical classification of slowly growing mycobacteria, including 159 strains received as M. tuberculosis, M. bovis, M. africanum and M. microti, was carried out using 88 characters. All 159 strains received as M. tuberculosis, M. bovis, M. africanum and M. microti formed 1 cluster and no clear-cut differentiation among these 4 spp. was achieved. These 4 spp. should be reduced to 1 spp, M. tuberculosis. Within the cluster, 2 subclusters appeared, with a number of strains located outside the subclusters. One subcluster was composed, except for 2 strains, of only M. tuberculosis strains, and another of M. bovis and M. africum strains only. The subclusters were regarded as ssp. tuberculosis and ssp. bovis, respectively. M. africanum was regarded as a synonym of M. bovis, i.e., a niacin-positive variety of M. bovis (ssp. bovis) . An intermediate subcluster was observed outside the M. tuberculosis and M. bovis subclusters. This may be regarded as intermediate between the 2 ssp. tuberculosis and bovi. In the last 2 decades, the characteristics of M. tuberculosis strains isolated from patients seemed to be approaching those of M. bovis strains. The recently isolated strains showed stronger arylsulfatase activity and lower resistance to thiophene-2-carboxylic acid hydrazide than the strains isolated 16-19 yr ago.

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