Mycobacterium tuberculosis
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mashal Awais, M.D.[2]; João André Alves Silva, M.D. [3]
Synonyms and keywords: M. Tuberculosis
Overview
Overview
Mycobacterium tuberculosis is the bacterium responsible for tuberculosis. M. tuberculosis is an obligate aerobe, non-encapsulated, non-motile, acid-fast bacillus. . M. tuberculosis is one of the Mycobacterium tuberculosis complex, which also includes bacteria, such as M. bovis and M. africanum. The bacterium has a very slow rate of replication, and its genetic variations account for the different strains and the growing drug resistance. M. tuberculosis has tropism for different kinds of human cells, with preference for cells of the lung. The main natural reservoir for M. tuberculosis are Human beings; however, the bacteria can also infect other species.
Taxonomy
Taxonomy
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Cellular organisms; bacteria; Actinobacteria; Actinobacteria; Actinobacteridae; Actinomycetales; Corynebacterineae; Mycobacteriaceae; Mycobacterium; Mycobacterium tuberculosis complex; M. tuberculosis[3]
Biology
Biology
- Mycobacterium tuberculosis belongs to the Mycobacterium tuberculosis complex. This complex includes M. tuberculosis, M. bovis, M. africanum, M. canetti, and M. microti.[4]
- M. tuberculosis is an obligate aerobe, non-encapsulated, non-motile, acid-fast bacillus.
- Its shape is slender, straight or slightly curved bacillus with rounded ends.
- It can be present singly, in pairs or in small groups or clumps.
- It cannot form spores.
- It favors tissues with high oxygen levels.
- Due to the high lipid and mycolic acid content of its cell wall, It stains weakly gram-positive or does not retain the dye.
- Microscopic examination of sputum samples cannot differentiate it from other acid-fast bacteria, such as Nocardia spp.[4]
- M. tuberculosis divides every 15-20 hours which is considered an extremely low rate of division. This feature, in addition to its ability to remain latent for long time, are responsible for the long treatment duration needed.[4]
- It can withstand dryness for weeks and also weak disinfectants.
- Genetic variations in the M. tuberculosis genome lead to important phenotypical changes. As a result, there are several variable strains of the bacteria, six of which have particular geographical distribution. Three strains, the Beijing family, strain W and the W-like strains, were reported to be associated with higher incidence of multi-drug resistance.[5][6]
Tropism
Tropism
There is no particular tissue tropism for M. tuberculosis and it can infect almost all human tissues. However, M. tuberculosis prefers tissues with high levels of oxygen , hence, pulmonary tuberculosis has the highest rate. [4]
Natural Reservoir
Natural Reservoir
The main natural reservoir for M. tuberculosis are Human beings; however, the bacteria can also infect other species.[4]
References
References
- ↑ “http://phil.cdc.gov/phil/details.asp”. External link in
|title=(help) - ↑ “http://phil.cdc.gov/phil/details.asp”. External link in
|title=(help) - ↑ “Mycobacterium tuberculosis”.
- ↑ 4.0 4.1 4.2 4.3 4.4 Lawn SD, Zumla AI (2011). “Tuberculosis”. Lancet. 378 (9785): 57–72. doi:10.1016/S0140-6736(10)62173-3. PMID 21420161.
- ↑ Smith NH, Hewinson RG, Kremer K, Brosch R, Gordon SV (2009). “Myths and misconceptions: the origin and evolution of Mycobacterium tuberculosis”. Nat Rev Microbiol. 7 (7): 537–44. doi:10.1038/nrmicro2165. PMID 19483712.
- ↑ Gagneux S, Small PM (2007). “Global phylogeography of Mycobacterium tuberculosis and implications for tuberculosis product development”. Lancet Infect Dis. 7 (5): 328–37. doi:10.1016/S1473-3099(07)70108-1. PMID 17448936.
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