Nontuberculous Mycobacteria (NTM) is a now technically out-dated group of occasionally pathogenic aerobic acid-fast bacilli microbes, formerly within the Mycobacterium genus, that notably excludes M. tuberculosis and M. leprae.
Although there are now >190 species thanks to genetic sequencing, there are some of more clinical relevance:
- Mycobacterium avium & Mycobacterium intracellulare ⇒ MAC
- Mycobacteroides abscessus
- Mycobacterium marinum ⇒ fish tank granuloma
- Mycobacterium kansasii
- Mycobacterium fortuitum
- Mycobacterium scrofulaceum ⇒ mycobacterial cervical lymphadenitis
NTM can be divided into rapid-growing and slow-growing species (relatively, as essentially all Mycobacterium are slow growing compared to other bacteria).
The rapid-growing species include:
- M. abscessus
- M. fortuitum
The slow-growing species include:
- MAC
- M. kansasii
- M. marinum
MAC primarily affects more immunocompetent hosts with pulmonary pathology (but can be widely disseminated especially with CD4 counts <50/µL).
M. kansasii primarily causes cavitary pulmonary disease, but can present with a cutaneous infection with appearance of lesions and lymphatic spread. Treated with rifampin.
The rapid-growing species often affect skin and soft tissue.