The open-ended study of the International Working Group on Mycobacterial Taxonomy is an ongoing project to characterize slowly growing strains of mycobacteria that do not belong to well-established or thoroughly characterized species. In this fourth report we describe two numerical taxonomic clusters that represent subspecies or biovars of Mycobacterium simiae, one cluster that encompasses the erstwhile type strain of the presently invalid species "Mycobacterium parafinicum," one cluster that is phenotypically very similar to Mycobacterium avium and Mycobacterium intraceltulare but may be a separate genospecies, one cluster that appears to be phenotypically distinct from M . aviurn but reacts with a nucleic acid probe specific for M . avium, and three tentatively defined clusters in proximity to a cluster that encompasses the type strain of Mycobacterium malmoense. Of special practical interest is the fact that one of the latter three clusters is composed of clinically significant scotochromogenic bacteria that can be misidentified as the nonpathogenic organism Mycobacterium gordonae if insufficient biochemical tests are performed.In their first cooperative studies, the members of the International Working Group on Mycobacterial Taxonomy (IWGMT) applied numerical taxonomic (NT) analysis methods to discrete and limited sets of mycobacteria to provide broad-based characterizations of clusters that corresponded to previously established species (5,10,12,16,26,31). Subsequently, a cooperative open-ended study was initiated in which new strains of slowly growing mycobacteria were introduced on a continuing basis, and the data were analyzed at intervals (32-34). The purpose of this study of an expanding set of cultures was to characterize slowly growing mycobacterial strains that represented uncommonly encountered species that had not been represented in the first six studies, as well as to recognize clusters of previously unknown taxa.A total of 38 new strains have been added to the openended study since the most recent report (341, and most of these fell into groups that exhibited phenotypic affinities to clusters that encompass the type strains of Mycohacterium simiae, M . intracellulare, M . avium, M . scrofulaceum, M . malmoense, and the presently invalid species " M . parafinicum." As noted in the previous report (34), these clusters are phenotypically less clearly resolved from one another than clusters that represent other species of slowly growing mycobacteria, and in this study we analyzed the expanded data base for these organisms. MATERIALS AND METHODS Selection of strains.The criteria for introducing new cultures into this study have been described previously (32,34 Editing and analysis of data. The criteria and editing programs for suppression of irrelevant, redundant, and incomplete data that were used in generating the NT matrices have been described previously (25,(32)(33)(34). Features were coded according to the RKC scheme of Rogosa et al. (15).NT analyses were based on simple matching coefficients,...

A tuberculin-active glycopeptide containing eight different amino acids and glucose was isolated from the protoplasm of Mycobacterium tuberculosis. A molecular weight of 4,000 to 5,000 was established by Sephadex gel filtration; other analyses showed a peptide to carbohydrate ratio of 9: 1. These observations suggest a tentative composition of 3 to 4 residues of glucose, 12 residues each of aspartic and glutamic acids, 3 residues each of lysine, glycine, and serine, and I residue each of arginine, threonine, and alanine.

Strains of scotochromogenic mycobacteria were studied by using numerical taxonomy methods in an attempt to more clearly define Mycobacterium szulgai and to find tests useful in identifying the species. In this study all strains of M. szulgai were strong reducers of nitrate, were slow in hydrolyzing Tween 80, and gave a high semiquantitative catalase reaction. Results obtained indicate that the use of increased pigmentation after 1 h of light exposure at 25 C and that the use of arylsulfatase activity are of questionable diagnostic value in separating the species from other scotochrompgenic mycobacteria.