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| __NOTOC__
| | #redirect[[Mycobacterium tuberculosis]] |
| {{Tuberculosis}}
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| {{CMG}}
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| ==Overview==
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| Tuberculosis, or TB is a bacterial infection that kills 3 million people worldwide, more people than any other infection in the world. Approximately one-third of the world is infected, and 15 million people in the US. Active tuberculosis kills 60% of the time if not treated, but treatment cures 90% of patients. Most people are infected with TB have latent TB. This means that the bacteria is controlled by the body's immune system. People with latent TB do not have symptoms and cannot transmit TB to other people. However, later if the infected person has a weakened immune system (AIDS, young children, elderly, sick with other diseases, etc.), the bacteria can break out leading to active TB, or TB disease.
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| ===Bacterial species===
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| {{main|Mycobacterium tuberculosis}}
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| {{#widget:SchemaSnippet}}
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| [[Image:Mycobacterium tuberculosis.jpg|300px|left|thumb|Scanning electron micrograph of ''[[Mycobacterium tuberculosis]]'']]
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| The primary cause of TB , ''[[Mycobacterium tuberculosis]]'' (M. TB), is an [[aerobic organism|aerobic]] [[bacterium]] that [[cell division|divides]] every 16 to 20 hours, an extremely slow rate compared with other bacteria, which usually divide in less than an hour.<ref name=Cox_2004>{{cite journal |author=Cox R |title=Quantitative relationships for specific growth rates and macromolecular compositions of ''Mycobacterium tuberculosis'', ''Streptomyces coelicolor'' A3(2) and ''Escherichia coli'' B/r: an integrative theoretical approach |journal=Microbiology |volume=150 |issue=Pt 5 |pages=1413–26 |year=2004 |url=http://mic.sgmjournals.org/cgi/content/full/150/5/1413?view=long&pmid=15133103#R35 | pmid = 15133103}}</ref> (For example, one of the fastest-growing bacteria is a strain of ''[[E. coli]]'' that can divide roughly every 20 minutes.) Since MTB has a cell wall but lacks a [[phospholipid]] [[Bacterial cell structure|outer membrane]], it is [[Tuberculosis classification|classified]] as a [[Gram-positive]] bacterium. However, if a [[Gram stain]] is performed, MTB either stains very weakly Gram-positive or does not retain dye due to the high lipid & mycolic acid content of its cell wall.<ref name=Madison_2001>{{cite journal |author=Madison B |title=Application of stains in clinical microbiology. |journal=Biotech Histochem |volume=76 |issue=3 |pages=119-25 |year=2001 |pmid=11475314}}</ref> MTB is a small rod-like [[bacillus]] that can withstand weak [[disinfectant]]s and survive in a [[Endospore|dry state]] for weeks. In nature, the bacterium can grow only within the cells of a [[host (biology)|host]] organism, but ''M. tuberculosis'' can be cultured ''[[in vitro]]''.<ref name=Parish_1999>{{cite journal |author=Parish T, Stoker N |title=Mycobacteria: bugs and bugbears (two steps forward and one step back) |journal=Mol Biotechnol |volume=13 |issue=3 |pages=191–200 |year=1999 | pmid = 10934532}}</ref>
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| Using certain [[histology|histological]] techniques on expectorate samples from [[phlegm]] (also called sputum), scientists can identify MTB under a regular microscope. Since MTB retains certain stains after being treated with acidic solution, it is classified as an [[acid-fast bacillus]] (AFB).<ref name=Madison_2001>{{cite journal |author=Madison B |title=Application of stains in clinical microbiology |journal=Biotech Histochem |volume=76 |issue=3 |pages=119-25 |year=2001 | pmid = 11475314}}</ref> The most common staining technique, the [[Ziehl-Neelsen stain]], dyes AFBs a bright red that stands out clearly against a blue background. Other ways to visualize AFBs include an [[auramine-rhodamine stain]] and [[Fluorescence microscope|fluorescent microscopy]].
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| The ''M. tuberculosis'' complex includes 3 other TB-causing [[mycobacterium|mycobacteria]]: ''[[Mycobacterium bovis|M. bovis]]'', ''[[Mycobacterium africanum|M. africanum]]'' and ''[[Mycobacterium microti|M. microti]]''. The first two only very rarely cause disease in [[immunocompetent]] people. On the other hand, although ''M. microti'' is not usually [[pathogen]]ic, it is possible that the [[prevalence]] of ''M. microti'' infections has been underestimated.<ref name=Niemann_2000>{{cite journal |author=Niemann S, Richter E, Dalügge-Tamm H, Schlesinger H, Graupner D, Königstein B, Gurath G, Greinert U, Rüsch-Gerdes S |title=Two cases of ''Mycobacterium microti'' derived tuberculosis in HIV-negative immunocompetent patients |journal=Emerg Infect Dis |volume=6 |issue=5 |pages=539-42 |year=2000 |pmid = 10998387}}</ref>
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| Other known pathogenic [[Mycobacterium|mycobacteria]] include ''[[Mycobacterium leprae]]'', [[Mycobacterium avium complex|''Mycobacterium avium'']] and ''M. kansasii''. The last two are part of the [[nontuberculous mycobacteria]] (NTM) group. Nontuberculous mycobacteria cause neither TB nor [[leprosy]], but they ''do'' cause pulmonary diseases resembling TB.<ref name=ALA_1997>{{cite journal |author= |title=Diagnosis and treatment of disease caused by nontuberculous mycobacteria. This official statement of the American Thoracic Society was approved by the Board of Directors, March 1997. Medical Section of the American Lung Association |journal=Am J Respir Crit Care Med |volume=156 |issue=2 Pt 2 |pages=S1–25 |year=1997 |pmid = 9279284}}</ref>
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| ===Evolution===
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| During its [[evolution]], ''M. tuberculosis'' has lost numerous [[Coding region|coding]] and non-coding regions in its [[genome]], losses that can be used to distinguish between strains of the bacteria. The implication is that ''M. tuberculosis'' strains differ geographically, so their genetic differences can be used to track the origins and movement of each strain.<ref name=Rao_2005>{{cite journal |author=Rao K, Kauser F, Srinivas S, Zanetti S, Sechi L, Ahmed N, Hasnain S |title=Analysis of genomic downsizing on the basis of region-of-difference polymorphism profiling of Mycobacterium tuberculosis patient isolates reveals geographic partitioning |journal=J Clin Microbiol |volume=43 |issue=12 |pages=5978–82 |year=2005 | pmid = 16333085}}</ref>
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| ==References==
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| {{reflist|2}}
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| [[Category:Disease]]
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| [[Category:Infectious disease]]
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| [[Category:Pulmonology]]
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