In related efforts, members of the International Working Group on Mycobacterial Taxonomy (IWGMT) made significant contributions to mycobacterial identification and taxonomy. However, these simple designations are not practical or sufficient for defining species within the Mycobacterium genus. Although this simple system is not used as extensively now, its longevity is demonstrated by references in publications and frequent communications between mycobacteriologists. “Rapid growers” were defined as having visible growth in <7 days, and they were designated group IV. The “slow growers” were defined as having visible growth in >7 days and were categorized in the following groups: group I, photochromogens group II, scotochromogens and group III, nonphotochromogens. A classification system based on pigmentation and growth rate was introduced to define the occurrence of “atypical” (a term presently in disfavor in mycobacterial nomenclature) strains and their relationship to the Mycobacterium species perceived as pathogenic ( 80, 95). When other Mycobacterium species were recognized as infectious agents, it was obvious that additional differentiation criteria were needed. These tests were designed to discriminate among mycobacteria involved in disease and were directed toward detecting Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium avium, or saprophytes (57–59). In this review, we assess its development and usefulness as an identification technique for Mycobacterium species.Įarly strategies employed to identify species of the Mycobacterium genus have included observations of staining properties of bacilli, cultural morphology, biochemical tests, and, rarely, the inoculation of susceptible animals with live bacilli for observation of animal pathogenicity. Over the last decade, high-performance liquid chromatography analysis of the mycolic acids has become an accepted method for identification of mycobacteria. However, only a few identification methods can detect the species diversity within the Mycobacterium genus.

Since clinical case management varies depending on the etiologic agent, laboratories must identify the species in a timely manner.

The ubiquitous nature of NTM, combined with their potential to be opportunistic pathogens in immunocompromised as well as nonimmunodeficient patients, further complicates the problem of their identification.

The identification processes are confounded by an increasing diversity of newly characterized NTM species. Nontuberculosis mycobacteria (NTM) causing other mycobacterioses can be difficult to identify. Mycobacterium tuberculosis is the etiologic agent of tuberculosis and can be accurately detected by laboratories using commercial genetic tests.

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