Taxonomic analysis of some slowly growing atypical mycobacteria

A taxonomic analysis of 92 strains of slowly growing mycobacteria received as members of 11 species of the genus Mycobacterium showed that the 45 characters used allowed to reliably recognize M. avium-intracellulare, M. xenopi, M. kansasii, M. shimoidei, M. terrae, M. nonchromogenicum and M. triviale as distinct species. A numerical taxonomic method revealed that strains of these species formed distinct clusters, which was confirmed by calculated mean values of intra- and intertaxon similarity. A close relatedness was found between M. scrofulaceum and M. avium-intracellulare species which could not be well differentiated from one another by the tests used. A small number of M. novum strains in the study did not allow a clearcut distinction between this taxon and similar strains of M. nonchromogenicum and M. terrae species. Both collection strains of M. gastri differed considerably from one another: one exhibited a certain relatedness to M. kansasii taxon, the other one to M. avium-intracellulare. This study allowed to prepare a table which presents the frequencies (%) of characters positivity for each of the taxa studied. The table is intended as a diagnostic tool in routine identification procedures conducted in field mycobacteriological laboratories.