Mycobacterium tuberculosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Soumya Sachdeva; João André Alves Silva, M.D. [2]
Overview
Mycobacterium tuberculosis is the bacterium that causes most cases of tuberculosis.[1] It was first described on March 24, 1882 by Robert Koch, who subsequently received the Nobel Prize in physiology or medicine for this discovery in 1905; the bacterium is also known as Koch's bacillus. The M. tuberculosis genome was sequenced in 1998.[2][3]
Taxonomy
Cellular organisms; Bacteria; Actinobacteria; Actinobacteria; Actinobacteridae; Actinomycetales; Corynebacterineae; Mycobacteriaceae; Mycobacterium; Mycobacterium tuberculosis complex; M. tuberculosis[4]
Biology
Mycobacterium tuberculosis belongs to the Mycobacterium tuberculosis complex. This complex includes M. tuberculosis, M. bovis, M. africanum, M. canetti, and M. microti.[5]
M. tuberculosis is an obligate aerobe, non-encapsulated, non-motile, acid-fast bacillus. It does not form spores and its ideal growing environment includes tissues with high levels of oxygen.[5]
While mycobacteria do not seem to fit the Gram-positive category from an empirical standpoint (i.e. they do not retain the crystal violet stain), they are classified as an acid-fast Gram positive bacterium due to their lack of an outer cell membrane.[1] M. tuberculosis divides every 15 to 20 hours—extremely slowly compared to other bacteria, which tend to have division times measured in minutes (for example, E. coli can divide roughly every 20 minutes). It is a small, rod-like bacillus that can withstand weak disinfectants and can survive in a dry state for weeks.
Structure
Slender, straight or slightly curved bacillus with rounded ends, occuring singly, in pairs or in small clumps. These bacilli are acid fast, non sporing, non capsulated and non motile.
Natural Reservoir
Human beings are the main natural reservoir for M. tuberculosis, however, the bacteria may infect other species.[5]
Resistance
Mycobacteria are killed at 60 degree celsius in 15-20 minutes. They are sensitive to UV rays and sunlight. They are relatively resistant to 5% phenol, 15% sulphuric acid, 5% oxalic acid, 4% sodium hydroxide. The bacillus are destroyed by tincture of sodium in five minutes and by 80% ethanol in 2-10 minutes.
References
- ↑ 1.0 1.1 Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.
- ↑ Cole ST; Brosch R; Parkhill J; et al. (1998). "Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence". Nature. 393: 537&ndash, 544.
- ↑ Camus JC; Pryor MJ; Medigue C; Cole ST. (148). "Re-annotation of the genome sequence of Mycobacterium tuberculosis H37Rv". Microbiology. 2002: 2967&ndash, 2973.
- ↑ "Poliovirus".
- ↑ 5.0 5.1 5.2 Lawn SD, Zumla AI (2011). "Tuberculosis". Lancet. 378 (9785): 57–72. doi:10.1016/S0140-6736(10)62173-3. PMID 21420161.