Revised classification of anonymous mycobacteria TABLE

Three methods for the laboratory classification of mycobacteria have been proposed. Runyon (1955) used pigment production and rate of growth to define four groups (numbered 1 to 4). Collins (1962) employed growth at 20°C. and 44°C., resistance to thiosemicarbazone, and growth in a synthetic medium to describe four similar groups (assemblies A to D). Marks and Richards (1963) used morphological, colonial, and cultural characteristics, growth at 25°C. and 42°C., and drug resistance to identify seven groups (numbered 1 to 7) of pathogenic mycobacteria. Each of these systems has disadvantages. Those of Runyon and Collins define only four groups, three of which are heterogenous. That of Marks and Richards does not include some mycobacteria commonly found in clinical material. Moreover, the tests employed by Runyon, and to some extent by Marks and Richards, are subjective and there is some difficulty in defining some of the groups of Marks and Richards on purely bacteriological grounds. The need for a revised clinical laboratory classification led us to re-examine the 199 strains studied in 1962 and to test an additional 121 strains. Forty species and unnamed strains from the National Collection of Type Cultures were also examined. Only those tests which can easily be performed in the clinical laboratory were used. For this reason the