Mycobacterium tuberculosis: Difference between revisions
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''Mycobacterium tuberculosis'' belongs to the Mycobacterium tuberculosis complex. This complex includes ''M. tuberculosis'', ''M. bovis'', ''M. africanum'', ''M. canetti'', and ''M. microti''.<ref name="pmid21420161">{{cite journal| author=Lawn SD, Zumla AI| title=Tuberculosis. | journal=Lancet | year= 2011 | volume= 378 | issue= 9785 | pages= 57-72 | pmid=21420161 | doi=10.1016/S0140-6736(10)62173-3 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21420161 }} </ref> | ''Mycobacterium tuberculosis'' belongs to the Mycobacterium tuberculosis complex. This complex includes ''M. tuberculosis'', ''M. bovis'', ''M. africanum'', ''M. canetti'', and ''M. microti''.<ref name="pmid21420161">{{cite journal| author=Lawn SD, Zumla AI| title=Tuberculosis. | journal=Lancet | year= 2011 | volume= 378 | issue= 9785 | pages= 57-72 | pmid=21420161 | doi=10.1016/S0140-6736(10)62173-3 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21420161 }} </ref> | ||
''M. tuberculosis'' is an [[obligate aerobe]], [[capsule|non-encapsulated]], [[motility|non-motile]], [[acid-fast]] [[bacillus]]. Slender, straight or slightly curved [[bacillus]] with rounded ends, occuring singly, in pairs or in small clumps. It does not form [[spores]] and its ideal growing environment includes tissues with high levels of [[oxygen]]. It cannot be considered gram-positive or gram-negative due to the high lipid content of the [[cell wall]], which is impermeable to the dyes used until combined with an alcohol. On microscopic examination of [[sputum]] samples, the bacteria cannot be distinguished from other [[acid-fast]] bacteria, such as [[Nocardia]] spp.<ref name="pmid21420161">{{cite journal| author=Lawn SD, Zumla AI| title=Tuberculosis. | journal=Lancet | year= 2011 | volume= 378 | issue= 9785 | pages= 57-72 | pmid=21420161 | doi=10.1016/S0140-6736(10)62173-3 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21420161 }} </ref> | ''M. tuberculosis'' is an [[obligate aerobe]], [[capsule|non-encapsulated]], [[motility|non-motile]], [[acid-fast]] [[bacillus]]. Slender, straight or slightly curved [[bacillus]] with rounded ends, occuring singly, in pairs or in small clumps. It does not form [[spores]] and its ideal growing environment includes tissues with high levels of [[oxygen]]. It cannot be considered gram-positive or gram-negative due to the high lipid content of the [[cell wall]], which is impermeable to the dyes used until combined with an alcohol. On microscopic examination of [[sputum]] samples, the bacteria cannot be distinguished from other [[acid-fast]] bacteria, such as [[Nocardia]] spp.<ref name="pmid21420161">{{cite journal| author=Lawn SD, Zumla AI| title=Tuberculosis. | journal=Lancet | year= 2011 | volume= 378 | issue= 9785 | pages= 57-72 | pmid=21420161 | doi=10.1016/S0140-6736(10)62173-3 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21420161 }} </ref> ''M. tuberculosis'' has a very slow rate of replication, taking about 15 to 20 hours to divide. This characteristic, added to its ability to remain in the latent state for long periods of time, account for the long treatment duration required.<ref name="pmid21420161">{{cite journal| author=Lawn SD, Zumla AI| title=Tuberculosis. | journal=Lancet | year= 2011 | volume= 378 | issue= 9785 | pages= 57-72 | pmid=21420161 | doi=10.1016/S0140-6736(10)62173-3 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21420161 }} </ref> | ||
''M. tuberculosis'' | Genetic variances in the ''M. tuberculosis'' [[genome]] lead to important [[phenotypical]] changes. There are many different [[strains]] of the bacteria, 6 of which have specific geographical distribution. Three [[strains]], the ''Beijing family'', ''strain W'' and the ''W-like strains'', were noted to be associated with resistance to treatment drugs.<ref name="pmid19483712">{{cite journal| author=Smith NH, Hewinson RG, Kremer K, Brosch R, Gordon SV| title=Myths and misconceptions: the origin and evolution of Mycobacterium tuberculosis. | journal=Nat Rev Microbiol | year= 2009 | volume= 7 | issue= 7 | pages= 537-44 | pmid=19483712 | doi=10.1038/nrmicro2165 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19483712 }} </ref><ref name="pmid17448936">{{cite journal| author=Gagneux S, Small PM| title=Global phylogeography of Mycobacterium tuberculosis and implications for tuberculosis product development. | journal=Lancet Infect Dis | year= 2007 | volume= 7 | issue= 5 | pages= 328-37 | pmid=17448936 | doi=10.1016/S1473-3099(07)70108-1 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17448936 }} </ref> | ||
==Tropism== | ==Tropism== | ||
Revision as of 18:00, 20 October 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Synonyms and keywords: M. Tuberculosis
Overview
Mycobacterium tuberculosis is the bacterium responsible for tuberculosis. It is an aerobic, non-encapsulated, non-motile, acid-fast bacillus. M. tuberculosis belongs to the Mycobacterium tuberculosis complex, that 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. It may infect different species, yet human beings are its frequent natural reservoir.
Taxonomy
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Cellular organisms; Bacteria; Actinobacteria; Actinobacteria; Actinobacteridae; Actinomycetales; Corynebacterineae; Mycobacteriaceae; Mycobacterium; Mycobacterium tuberculosis complex; M. tuberculosis[3]
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. Slender, straight or slightly curved bacillus with rounded ends, occuring singly, in pairs or in small clumps. It does not form spores and its ideal growing environment includes tissues with high levels of oxygen. It cannot be considered gram-positive or gram-negative due to the high lipid content of the cell wall, which is impermeable to the dyes used until combined with an alcohol. On microscopic examination of sputum samples, the bacteria cannot be distinguished from other acid-fast bacteria, such as Nocardia spp.[4] M. tuberculosis has a very slow rate of replication, taking about 15 to 20 hours to divide. This characteristic, added to its ability to remain in the latent state for long periods of time, account for the long treatment duration required.[4]
Genetic variances in the M. tuberculosis genome lead to important phenotypical changes. There are many different strains of the bacteria, 6 of which have specific geographical distribution. Three strains, the Beijing family, strain W and the W-like strains, were noted to be associated with resistance to treatment drugs.[5][6]
Tropism
M. tuberculosis can infect different cells of the human body, however, due to its preference for tissues with high oxygen levels, its cellular tropism is mostly directed towards lung cells.[4]
Natural Reservoir
Human beings are the main natural reservoir for M. tuberculosis, however, the bacteria may infect other species.[4]
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.