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Microbiology of nontuberculous mycobacteria

David E Griffith, MD
Section Editor
C Fordham von Reyn, MD
Deputy Editor
Allyson Bloom, MD


Mycobacterial species other than Mycobacterium tuberculosis and Mycobacterium leprae are generally free-living organisms that are ubiquitous in the environment. They have been recovered from water, soil, domestic and wild animals, milk, and food [1-4]. As the incidence of tuberculosis (TB) declined in areas of the world where socioeconomic conditions were rapidly advancing, the frequency of isolating nontuberculous mycobacteria (NTM) began to increase, and their relevance to human disease became apparent [5].

In 1959, Runyon proposed the first classification system for these organisms that divided human isolates of NTM into four groups on the basis of growth rates, colony morphology, and pigmentation in the presence and absence of light (table 1) [6]. Though now outdated, this classification allowed mycobacterial laboratories to more readily identify individual species of NTM, resulting in clearer characterization of distinct diseases or syndromes associated with these organisms.

With the availability of 16S ribosomal DNA sequencing and high-performance liquid chromatography (HPLC), and polymerase chain reaction-restriction length polymorphism analysis (PRA), the number of new species of NTM has risen dramatically with the naming of species such as Mycobacterium genavense, Mycobacterium interjectum, Mycobacterium triplex, Mycobacterium celatum, and Mycobacterium lentiflavum. Over 160 species have been recognized in the genus Mycobacterium [7].

The microbiology of NTM will be reviewed here. Other issues related to NTM are discussed separately. (See "Diagnosis of nontuberculous mycobacterial infections of the lungs in HIV-negative patients" and "Pathogenesis of nontuberculous mycobacterial infections" and "Treatment of Mycobacterium avium complex lung infection in adults".)


Within the genus Mycobacterium, four groups of human pathogens can be delineated on the basis of microbiologic, clinical, and epidemiologic characteristics (table 1):

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Literature review current through: Nov 2017. | This topic last updated: Aug 18, 2016.
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