Mycobacterium leprae 453262 222830777 2008-07-01T09:30:15Z DOI bot 6652755 Citation maintenance. Formatted: pages. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Taxobox | color = lightgrey | name = ''Mycobacterium leprae'' | image = Mycobacterium_leprae.jpeg | image_width = 200px | image_caption = Microphotograph of ''Mycobacterium leprae'' taken from a skin lesion. Source: CDC | regnum = [[Bacterium|Bacteria]] | phylum = [[Actinobacteria]] | ordo = [[Actinomycetales]] | subordo = [[Corynebacterineae]] | familia = [[Mycobacterium|Mycobacteriaceae]] | genus = ''[[Mycobacterium]]'' | species = '''''M. leprae''''' | binomial = ''Mycobacterium leprae'' | binomial_authority = [[Gerhard Armauer Hansen|Hansen]], 1874 }} '''''Mycobacterium leprae''''', also known as '''Hansen’s bacillus''', mostly found in warm tropical countries, is the [[bacterium]] that causes [[leprosy]] (Hansen's disease).<ref name=Sherris>{{cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | pages = 451-3 | publisher = McGraw Hill | year = 2004 | isbn = 0838585299}}</ref> It is an intracellular, [[Pleomorphism|pleomorphic]], [[acid-fast]] bacterium.<ref name=Baron>{{cite book | author = McMurray DN | title = Mycobacteria and Nocardia. ''in:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.1833 | isbn = 0-9631172-1-1 }}</ref> ''M. leprae'' is a [[Gram-positive bacteria|Gram-positive]], [[Aerobic organism|aerobic]] rod-shaped (bacillus) surrounded by the characteristic waxy coating unique to [[Mycobacterium|mycobacteria]]. In size and shape, it closely resembles ''[[Mycobacterium tuberculosis]]''. Due to its thick waxy coating, ''M. leprae'' stains with a carbol fuscin rather than with the traditional [[Gram stain]]. The culture takes several weeks to mature. Optical microscopy shows ''M. leprae'' in clumps, rounded masses, or in groups of bacilli side by side. It was discovered in [[1873]] by the Norwegian physician [[Gerhard Armauer Hansen]], who was searching for the bacteria in the skin nodules of patients with leprosy. It was the first bacterium to be identified as causing disease in man. <ref name=Hansen_1874>{{cite journal | author = Hansen GHA | title = Undersøgelser Angående Spedalskhedens Årsager (Investigations concerning the etiology of leprosy) | journal = Norsk Mag. Laegervidenskaben | year = 1874 | volume = 4| pages = pp. 1–88 | language = Norwegian }}</ref><ref name=Irgens_2002>{{cite journal |author=Irgens L |title=The discovery of the leprosy bacillus |journal=Tidsskr Nor Laegeforen |volume=122 |issue=7 |pages=708–9 |year=2002 |pmid=11998735}}</ref> The organism has never been successfully grown on an artificial cell culture media.<ref name=Baron /> Instead it has been grown in mouse foot pads and more recently in nine-banded [[armadillo]]s because they, like humans, are susceptible to leprosy. This can be used as a diagnostic test for the presence of bacillus in body lesions of suspected leprosy patients. The difficulty in culturing the organism appears to be because the organism is an [[obligate intracellular parasite]] that lacks many necessary genes for independent survival. The complex and unique cell wall that makes members of the ''[[Mycobacterium]]'' genus difficult to destroy is apparently also the reason for the extremely slow replication rate. Virulence factors include a waxy exterior coating, formed by the production of [[mycolic acid]]s unique to ''[[Mycobacterium]]''. ''M. leprae'' was sensitive to [[dapsone]] (diaminodiphenylsulfone, the first effective treatment which was discovered for leprosy in the 1940s), but [[antibiotic resistance|resistance]] against this [[antibiotic]] has developed over time. Therapy with dapsone alone is now strongly contraindicated. Currently, a multidrug treatment (MDT) is recommended by the [[World Health Organization]], including [[dapsone]], [[rifampicin]] and [[clofazimine]]. In patients receiving the MDT, a high proportion of the [[bacilli]] die within a short amount of time without immediate relief of symptoms. This suggests that many symptoms of leprosy must be due in part to the presence of dead cells. == ''Mycobacterium leprae'' genome == ''Mycobacterium leprae'' has the longest doubling time of all known bacteria and has thwarted every effort at culture in the laboratory.<ref name=Truman_2001>{{cite journal |author=Truman RW, Krahenbuhl JL |title=Viable M. leprae as a research reagent |journal=Int. J. Lepr. Other Mycobact. Dis. |volume=69 |issue=1 |pages=1–12 |year=2001 |pmid=11480310}}</ref> Comparing the [[genome]] sequence of ''Mycobacterium leprae'' with that of ''[[Mycobacterium tuberculosis]]'' provides clear explanations for these properties and reveal an extreme case of reductive [[evolution]]. Less than half of the genome contains functional [[genes]]. Gene deletion and decay appear to have eliminated many important [[metabolic]] activities, including [[siderophore]] production, part of the oxidative and most of the [[microaerophilic]] and [[anaerobic]] [[Respiration (physiology)|respiratory]] chains, and numerous [[catabolic]] systems and their regulatory circuits. <ref name=Cole_1998>{{cite journal |author=Cole ST, Brosch R, Parkhill J, ''et al'' |title=Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence |journal=Nature |volume=393 |issue=6685 |pages=537–44 |year=1998 |pmid=9634230 |doi=10.1038/31159}}</ref> The genome sequence of a strain of ''M. leprae'', originally isolated in [[Tamil Nadu]] and designated ''TN'', has been completed recently. The sequence was obtained by a combined approach, employing automated [[DNA]] sequence analysis of selected [[cosmids]] and whole-genome 'shotgun' clones. After the finishing process, the genome sequence was found to contain 3,268,203 [[base pair]]s (bp), and to have an average [[GC-content|G+C content]] of 57.8%, values much lower than the corresponding values for ''M. tuberculosis'', which are 4, 441,529 bp and 65.6% G+C. There are 1500 genes which are common to both ''M. leprae'' and ''M. tuberculosis''. The comparative analysis suggests that both mycobacteria derived from a common ancestor and, at one stage, had [[gene pool]]s of similar size. Downsizing from a genome of 4.42 Mb, such as that of ''M. tuberculosis'', to one of 3.27 Mb would account for the loss of some 1200 [[protein]] coding sequences. There is evidence that many of the genes that were present in the genome of ''M. leprae'' have truly been lost. <ref name=Cole_2001>{{cite journal |author=Cole ST, Eiglmeier K, Parkhill J, ''et al'' |title=Massive gene decay in the leprosy bacillus |journal=Nature |volume=409 |issue=6823 |pages=1007–11 |year=2001 |pmid=11234002 |doi=10.1038/35059006}}</ref> Information from the completed genome can be useful to develop diagnostic skin tests, understanding the mechanism of nerve damage, drug resistance and to identify novel drug targets for rational design of new therapeutic regimens and drugs to treat leprosy and its complications. ==External links== * [http://www.sanger.ac.uk/Projects/M_leprae The genome of ''Mycobacterium leprae ''] * [http://microbes.historique.net/leprae.html "Mycobacterium leprae" Quick Reference] ==References== <!-- --------------------------------------------------------------- See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for a discussion of different citation methods and how to generate footnotes using the <ref> & </ref> tags and the {{Reflist}} template -------------------------------------------------------------------- --> {{Reflist}} [[Category:Acid fast bacilli]] [[Category:Corynebacterineae]] [[Category:Leprosy]] [[de:Mycobacterium leprae]] [[es:Mycobacterium leprae]] [[fr:Mycobacterium leprae]] [[id:Mycobacterium leprae]] [[it:Mycobacterium leprae]] [[he:Mycobacterium leprae]] [[la:Mycobacterium leprae]] [[nl:Mycobacterium leprae]] [[ja:らい菌]] [[no:Leprabasill]] [[pt:Mycobacterium leprae]] [[ro:Mycobacterium leprae]] [[sl:Mycobacterium leprae]] [[tr:Mycobacterium leprae]] [[zh:麻风杆菌]]