Comprehensive Numerical Classification of 369 Strains of Mycobacterium, Rhodococcus, and Nocardia

A numerical analysis of 369 strains received as members of the genus Mycobacterium, Rhodococcus (formerly Gordona), Nocardia, or Corynebacterium was carried out using 88 characters. Of the strains tested, 345 mycobacteria, rhodococci, and nocardiae formed four distinct clusters at a similarity level of 85%. The first cluster was composed of slowly growing mycobacteria; the second cluster, of strains of Mycobacterium flavescens and M. thermoresistibile; the third cluster, of strains of rapidly growing mycobacteria; and the fourth cluster, of strains of Rhodococcus and Nocardia. Strains of three species of rapidly growing mycobacteria, M. agri, M. smegmatis, and M. vaccae, were located outside of these clusters. The fourth cluster could be divided into three subclusters, one consisting of rhodococci plus some strains of Nocardia asteroides, a second consisting of the remaining strains of Nocardia, and a third consisting of strains of Rhodococcus aurantiacus (Gordona aurantiaca) and Jensenia canicruria.