Table 1.
Short characteristics of NTM groups [based on Runyon (1959); Herdman and Steele (2004); Salvana et al. (2007); Abdalla et al. (2009); Tortoli (2014); Koh (2017); Tortoli et al. (2017); Sharma and Upadhyay (2020)]
| Classification | Growth rate | Characteristics | Common examples |
|---|---|---|---|
| Group 1 | Slow-growing | Photochromogenic: Develop pigment when exposed to light. | Mycobacterium kansasii, Mycobacterium marinum |
| Group 2 | Slow-growing | Scotochromogenic: Produce pigment in both light and darkness. | Mycobacterium scrofulaceum, Mycobacterium szulgai, Mycobacterium gordonae |
| Group 3 | Slow-growing | Non-photochromogenic: Do not produce pigments. | MAC, Mycobacterium ulcerans |
| Group 4 | Fast-growing | May or may not produce colored colonies. | Mycobacterium fortuitum, Mycobacterium abscessus, Mycobacterium chelonae |
Fig 1.
Risk factors contributing to NTM infections. The risk factors for NTM infection can be broadly categorized into environmental exposures, underlying health conditions, lifestyle factors, and certain procedural or occupational hazards. CGD, chronic granulomatous disease; COPD, chronic obstructive pulmonary disease; GvH, graft versus host; IFN, interferon; IL, interleukin; NTM, non-tuberculous mycobacteria; SCID, severe combined immunodeficiency.
Fig 2.
Immune mechanisms accompanying mycobacterial infection. GM-CSF, granulocyte-macrophage colony-stimulating factor; IFN, interferon; IL, interleukin; MCAF, monocyte chemotactic and activating factor; MIF, migration inhibitory factor; RNS, reactive nitrogen species; ROS, reactive oxygen species; TNF, tumor necrosis factor.