Nontuberculous mycobacteria
924276
219623520
2008-06-16T03:20:45Z
24.8.148.6
/* External links */
'''Nontuberculous mycobacteria''' (NTM), also known as '''environmental mycobacteria''', '''atypical mycobacteria''' and '''mycobacteria other than tuberculosis''' (MOTT), are [[mycobacteria]] which do not cause [[tuberculosis]] or [[Leprosy|Hansen's disease]] (also known as leprosy).
==Introduction==
Mycobacteria are a family of small, rod-shaped bacilli that can be classified into 3 main groups for the purpose of diagnosis and treatment:
* ''[[Mycobacterium tuberculosis]]'' complex which can cause [[tuberculosis]]: ''[[Mycobacterium tuberculosis|M. tuberculosis]]'', ''[[Mycobacterium bovis|M. bovis]]'', ''[[M. africanum]]'', , ''[[M. microti]]'' and ''[[M. canetti]]''.
* ''[[Mycobacterium leprae|M. leprae]]'' which causes [[Leprosy|Hansen's disease]] or leprosy.
* Nontuberculous mycobacteria (NTM) are all the other mycobacteria which can cause pulmonary disease resembling tuberculosis, lymphadenitis, skin disease, or disseminated disease.
==Taxonomy==
In 1959, botanist Ernest Runyon put these human disease-associated bacteria into four groups:<ref name="G221">Grange, p. 221</ref>
*Photochromogens, which develop pigments in or after being exposed to light. Examples include ''[[M. kansasii]]'', ''[[M. simiae]]'' and ''[[M. marinum]]''.<ref name="G221"/>
*Scotochromogens, which become pigmented in darkness. Examples include ''[[M. scrofulaceum]]'' and ''[[M. szulgai]]''.<ref name="G221"/>
*Non-chromogens, which includes a group of prevalent opportunistic pathogens called [[Mycobacterium avium complex|''M. avium'' complex]] (MAC). Other examples are ''[[M. ulcerans]]'', ''[[M. xenopi]]'', ''[[M. malmoense]]'', ''[[M. terrae]]'', ''[[M. haemophilum]]'' and ''[[M. genavense]]''.<ref name="G222">Grange, p. 221</ref>
*Rapid growers include four well recognized pathogenic rapidly growing non-chromogenic species: ''[[M. chelonae]]'', ''[[M. abscessus]]'', ''[[M. fortuitum]]'' and ''[[M. peregrinum]]''. Other examples cause disease rarely, such as ''[[M. smegmatis]]'' and ''[[M. flavescens]]''.<ref name="G222"/>
The number of identified and cataloged NTM species has been increasing rapidly, from about 50 in 1997 to over 125 by January 2007. The surge is mainly due to improved isolation and identification technique.<ref>American Thoracic Society, p.369</ref>
==Epidemiology==
NTM are widely distributed in the environment, particularly in wet soil, marshland, streams, rivers and estuaries. Different species of NTM prefer different types of environment.<ref>Grange, p. 226</ref> Human disease is believed to be acquired from environmental exposures, and unlike tuberculosis and leprosy, there has been no evidence of animal-to-human or human-to-human transmission of NTM, hence the alternative label "environmental bacteria".<ref name="ATS370">American Thoracic Society, p. 370</ref>
NTM diseases have been seen in most industrialized countries, where incidence rates vary from 1.0 to 1.8 cases per 100,000 persons. Recent studies, including one done in Ontario, Canada, suggest that incidence is much higher. Pulmonary NTM is estimated by some experts in the field to be at least ten times more common than TB in the U.S., with at least 150,000 cases per year.
Most NTM disease cases involve the species MAC, M. abscessus, M. fortuitum and M. kansasii. M. abscessus is being seen with increasing frequency and is particularly difficult to treat. <ref name="ATS370"/>
==Pathogenesis==
The most common clinical manifestation of NTM disease is lung disease, but lymphatic, skin/soft tissue, and disseminated disease are also important.<ref name="ATS370"/>
Pulmonary disease caused by NTM is most often seen in post-menopausal women. It is not uncommon for Cystic Fibrosis, Alpha-1, Marfan's and Primary Ciliary Dyskenesia patients to have pulmonary NTM colonization and/or infection. Pulmonary NTM can also be found in individuals with [[AIDS]] and malignant disease. It can be caused by many NTM species which depends on region, but most frequently MAC and ''M. kansasii''.<ref name="G225">Grange, p. 225</ref>
[[Lymphadenitis]] can be caused by various species that is different from one place to another; but again, MAC is the main cause worldwide. Most patient are aged less than 5 years, but the incidence is rare for children having [[BCG vaccine]]. The disease has a high curability.<ref name="G223">Grange, p. 223</ref>
Soft tissue disease due to NTM infection include post-traumatic abscesses (caused by rapid growers), [[swimming pool granuloma]] (caused by ''M. marinum'') and [[Buruli ulcer]] (caused by ''M. ulcerans'' or ''M. shinshuense''). Post-traumatic abscesses most commonly occur after injection.<ref name="G223"/>
Disseminated mycobacterial disease is common in US and Europe in AIDS patient in the 1980s and early 1990s, though the incidence has declined in developed nations since the introduction of highly active antiretroviral therapy. It can also happen in individuals after having renal transplantation.<ref name="G225"/>
==Diagnosis==
Diagnosis of opportunistic mycobacteria is made by repeated isolation and identification of the pathogen with compatible clinical and radiological features. Similar to ''M. tuberculosis'', most nontuberculous mycobacteria can be detected microscopically and grow on [[Löwenstein-Jensen medium]].<ref name="G225"/> Many reference centres now use a nucleic acid-based method such as sequence differences detection in the gene coding for 16S ribosomal RNA to identify the species.<ref>Grange, p. 226</ref>
Pulmonary NTM disease diagnosis requires both identification of the mycobacterium in the patient's lung(s) as well as a high resolution CT scan of the lungs.
==Research==
Virginia Tech is conducting a home water supply and patient sputum comparison study to determine source of infection in pulmonary NTM cases. This study was funded by NTM Info & Research and results will be available by mid-2009.
An epidemiology study on pulmonary NTM is currently being conducted by National Institute of Allergy & Infectious Disease and Kaiser Permanente in southern California. Results will be available by mid-2009. This study was funded by NTM Info & Research.
French researchers finalized the genome sequence of M. abscessus in March 2008. The genome is available at http://www.ncbi.nlm.nih.gov/sites/entrez?db=genome&cmd=search&term=abscessus.
McGill University in Montreal, Canada is conducting a study to determine the genome sequence (type strain) of M. avium intracellulare. This study is partially funded by NTM Info & Research and results will be available by late 2009.
==Notes==
<references/>
==References==
* Griffith, David E.; Aksamit, Timothy; & A. Brown-Elliott, Barbara et al. (2007). [http://www.thoracic.org/sections/publications/statements/pages/mtpi/nontuberculous-mycobacterial-diseases.html American Thoracic Society Guidelines: Diagnosis, Treatment and Prevention of Nontuberculous Mycobacterial Diseases.] Am. J. Respiratory and Critical Care Medicine, Vol. 175, pp. 367-417.
* Grange, J. M. (2007). "Environmental mycobacteria". In Greenwood, David; Slack, Richard; Peitherer, John; & Barer, Mike (Eds.), ''Medical Microbiology'' (17th ed.), pp. 221-227. Elsevier. ISBN 978-0-443-10209-7.
==External links==
*[http://www.stopntmnow.com/ Stop NTM Now]
* [http://www.nationaljewish.org/disease-info/diseases/nts-mycobac/progs/index.aspx National Jewish Medical and Research Center]
* [http://www.uthct.edu/research/microbiology/forthepatient.asp University of Texas, Tyler Health Center]
*[http://www.emedicine.com/radio/topic413.htm Lung, Nontuberculous Mycobacterial Infections from eMedicine Radiology]
*[http://www.ntmhandbook.com/ The NTM Handbook: A Guide for Patients with Nontuberculous Mycobacterial Infections Including MAC]
[[Category:Nontuberculous mycobacteria|*]]
[[Category:Tuberculosis]]
[[Category:Bacteriology]]
[[Category:Bacterial diseases]]
[[Category:Pulmonology]]
[[Category:Microbiology]]
[[de:MOTT]]
[[pl:MOTT]]