Mycobacterium leprae - wikipedia Mycobacterium leprae Mycobacterium leprae Microphotograph of Mycobacterium leprae, the small brick - red rods in clusters, taken from a skin lesion. Source : CDC Scientific classification Domain : Bacteria Phylum : Actinobacteria Class : Actinobacteria Order : Actinomycetales Suborder : Corynebacterineae Family : Mycobacteriaceae Genus : Mycobacterium Species : M. leprae Binomial name Mycobacterium leprae Hansen, 1874 Mycobacterium leprae, also known as Hansen 's bacillus spirilly, mostly found in warm tropical countries, is a bacterium that causes leprosy ( Hansen 's disease ). It is an intracellular, pleomorphic, acid - fast, pathogenic bacterium. M. leprae is an aerobic bacillus ( rod - shaped ) surrounded by the characteristic waxy coating unique to mycobacteria. In size and shape, it closely resembles Mycobacterium tuberculosis. Due to its thick waxy coating, M. leprae stains with a carbol fuchsin 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, and ranging from 1 -- 8 μm in length and 0.2 -- 0.5 μm in diameter. 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 humans. The organism has never been successfully grown on an artificial cell culture medium. Instead, it has been grown in mouse foot pads and more recently in nine - banded armadillos because they, like humans, are susceptible to leprosy. This can be used as a diagnostic test for the presence of bacilli in body lesions of suspected leprosy patients. The difficulty in culturing the organism appears to be because it 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 acids unique to Mycobacterium. Mycobacterium leprae was sensitive to dapsone ( diaminodiphenylsulfone, the first effective treatment which was discovered for leprosy in the 1940s ), but 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 many symptoms of leprosy must be due in part to the presence of dead cells. Contents 1 Pathogenesis 2 Genome 2.1 Evolution and pseudogenes 2.2 Applications 3 Ancient Mycobacterium leprae 4 Evolution 5 Diagnostic criteria for leprosy 6 Treatment 7 References 8 External links Pathogenesis The incubation period of M. leprae can range between nine months and twenty years. It replicates intracellularly inside histiocytes and nerve cells and has two forms. One form is tuberculoid, which induces a cell - mediated response that limits its growth. Through this form M. leprae multiplies at the site of entry, usually the skin, invading and colonizing Schwann cells. The microbe then induces T - helper lymphocytes, epitheloid cells, and giant cell infiltration of the skin, causing infected individuals to exhibit large flattened patches with raised and elevated red edges on their skin. These patches have dry, pale, hairless centers, accompanied by a loss of sensation on the skin. The loss of sensation may develop as a result of invasion of the peripheral sensory nerves. The macule at the cutaneous site of entry and the loss of pain sensation are key clinical indications that an individual has a tuberculoid form of leprosy. The second form of leprosy is the lepromatous form. This form of the microbe proliferates within the macrophages at the site of entry. It also grows within the epithelial tissues of the face and ear lobes. The suppressor T - cells that are induced are numerous, however the epithelioid and giant cells are rare or absent. With cell - mediated immunity impaired, large numbers of M. leprae appear in the macrophages and the infected patients develop papules at the entry site, marked by a folding of the skin. Gradual destruction of cutaneous nerves lead to what is referred to as `` classic lion face ''. Extensive penetration of this microbe may lead to severe body damage ; for example the loss of bones, fingers, and toes. Genome Mycobacterium leprae has the longest doubling time of all known bacteria and has thwarted every effort at culture in the laboratory. Comparing the genome sequence of M. leprae with that of M. tuberculosis provides clear explanations for these properties, and reveals 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 respiratory chains, and numerous catabolic systems and their regulatory circuits. The first genome sequence of a strain of M. leprae, was completed in 1998. The genome sequence of a strain originally isolated in Tamil Nadu, India and designated TN, was completed in 2013. 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 pairs ( bp ), and to have an average 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. Evolution and pseudogenes Mycobacterium leprae has undergone a dramatic reduction in genome size with the loss of many genes. This genome reduction is not complete and numerous genes are still present as non-functional pseudogenes. Downsizing from a genome of 4.42 Mbp, such as that of M. tuberculosis, to one of 3.27 Mbp 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 the common ancestor of M. leprae and M. tuberculosis have been lost in the M. leprae genome. 1500 genes are still common to both M. leprae and M. tuberculosis. Applications Information from the completed genome can be useful to develop diagnostic skin tests, to understand the mechanisms of nerve damage and drug resistance and to identify novel drug targets for rational design of new therapeutic regimens and drugs to treat leprosy and its complications. Ancient Mycobacterium leprae Almost complete sequences of M. leprae from medieval skeletons with osteological lesions suggestive of leprosy from different Europe geographic origins were obtained using DNA capture techniques and high - throughput sequencing ( HTS ). Ancient sequences were compared with those of modern strains from biopsies of leprosy patients representing diverse genotypes and geographic origins, giving new insights in the understanding of evolution, course through history, phylogeography of the leprosy bacillus and the disappearance of leprosy from Europe Verena J. Schuenemann et al. demonstrated a remarkable genomic conservation during the past 1000 years and a close similarity between modern and ancient strains, suggesting that the sudden decline of leprosy in Europe was not due to a losing of virulence but due to extraneous factors, such as other infectious diseases, changes in host immunity or improved social conditions. The geographic occurrence of M. leprae include : Angola, Brazil, Central African Republic, Democratic Republic of Congo, Federated States of Micronesia, India, Kiribati, Madagascar, Nepal, Republic of Marshall Islands, and United Republic of Tanzania. Evolution The closest relative to Mycobacterium leprae is Mycobacterium lepromatosis. These species diverged 13.9 million years ago ( 95 % highest posterior density 8.2 million years ago -- 21.4 million years ago ) The most recent common ancestor of the extant M. leprae strains was calculated to have lived 3,607 years ago ( 95 % highest posterior density 2204 -- 5525 years ago ). The estimated mutation rate was The estimated substitution rate was 7.67 x 10 substitutions per site per year - similar to other bacteria. A study of genomes isolated from medieval cases estimated the mutation rate to be 6.13 × 10. The authors also showed that the leprosy bacillus in the Americas was brought there from Europe. It has been estimated that the ancestors of M. leprae and M. tuberculosis separated 36 million years ago. Another study suggested that M. leprae originated in East Africa and spread from there to Europe and the Middle East initially before spreading to West Africa and the Americas in the last 500 years. Diagnostic criteria for leprosy Diagnostic criteria for leprosy : The diagnosis of leprosy is primarily a clinical one. In one Ethiopian study, the following criteria had a sensitivity of 94 % with a positive predictive value of 98 % in diagnosing leprosy. Diagnosis was based on one or more of three signs : Hypopigmented or reddish skin patches with definite loss of sensation Thickened peripheral nerves Acid - fast bacilli on skin smears or biopsy material Treatment Multidrug therapy ( MDT ). Antibiotics that destroy M. leprae bacilli include : dapsone, rifampin, clofazamine, fluoroquinolones, macrolides, and minocycline. A preventative measure of M. leprae is to avoid close contact with infectious people who are untreated. The Bacillus Calmette -- Guérin ( BCG ) vaccine offers a variable amount of protection against leprosy in addition to its main target of tuberculosis. Armadillos are also known hosts for Mycobacterium leprae and have infected humans in the southeastern United States, although the geographic range of the disease and its complexity has been spreading. References Jump up ^ Ryan KJ, Ray CG, eds. ( 2004 ). Sherris Medical Microbiology ( 4th ed. ). McGraw Hill. pp. 451 -- 3. ISBN 0 - 8385 - 8529 - 9. ^ Jump up to : McMurray DN ( 1996 ). `` Mycobacteria and Nocardia. ''. In Baron S. ; et al. Baron 's Medical Microbiology ( 4th ed. ). University of Texas Medical Branch. ISBN 0 - 9631172 - 1 - 1. Jump up ^ Shinnick, Thomas M. ( 2006 ). `` Mycobacterium leprae ''. In Dworkin, Martin ; Falkow, Stanley ; Rosenberg, Eugene ; Schleifer, Karl - Heinz ; Stackebrandt, Erko. The Prokaryotes. Springer. pp. 934 -- 944. doi : 10.1007 / 0 - 387 - 30743 - 5_35. ISBN 978 - 0 - 387 - 25493 - 7. Jump up ^ Hansen GHA ( 1874 ). `` Undersøgelser Angående Spedalskhedens Årsager ( Investigations concerning the etiology of leprosy ) ''. Norsk Mag. Laegervidenskaben ( in Norwegian ). 4 : 1 -- 88. Jump up ^ Irgens L ( 2002 ). `` The discovery of the leprosy bacillus ''. Tidsskr nor Laegeforen. 122 ( 7 ) : 708 -- 9. PMID 11998735. Jump up ^ `` Leprosy ( Hansen 's disease ) - Blue Book - Department of Health and Human services, Victoria, Australia ''. ideas.health.vic.gov.au. Retrieved 2015 - 11 - 17. Jump up ^ Truman RW, Krahenbuhl JL ; Krahenbuhl ( 2001 ). `` Viable M. leprae as a research reagent ''. Int. J. Lepr. Other Mycobact. Dis. 69 ( 1 ) : 1 -- 12. PMID 11480310. ^ Jump up to : Cole ST, Brosch R, Parkhill J, et al. ( 1998 ). `` Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence ''. Nature. 393 ( 6685 ) : 537 -- 44. doi : 10.1038 / 31159. PMID 9634230. Jump up ^ Narayanan S, Deshpande U ; Deshpande ( 2013 ). `` Whole - Genome Sequences of Four Clinical Isolates of Mycobacterium tuberculosis from Tamil Nadu, South India ''. Genome Announc. 1 ( 3 ) : e00186 -- 13. doi : 10.1128 / genomeA. 00186 - 13. PMC 3707582. PMID 23788533. Jump up ^ Cole ST, Eiglmeier K, Parkhill J, et al. ( 2001 ). `` Massive gene decay in the leprosy bacillus ''. Nature. 409 ( 6823 ) : 1007 -- 11. doi : 10.1038 / 35059006. PMID 11234002. Jump up ^ Schuenemann VJ, Singh P, Mendum TA, et al. ( July 2013 ). `` Genome - wide comparison of medieval and modern Mycobacterium leprae ''. Science. 341 ( 6142 ) : 179 -- 83. doi : 10.1126 / science. 1238286. PMID 23765279. Jump up ^ `` Risk of Exposure Hansen 's Disease ( Leprosy ) CDC ''. www.cdc.gov. Retrieved 2015 - 11 - 17. Jump up ^ Singh P, Benjak A, Schuenemann VJ, Herbig A, Avanzi C, Busso P, Nieselt K, Krause J, Vera - Cabrera L, Cole ST ( 2015 ) Insight into the evolution and origin of leprosy bacilli from the genome sequence of Mycobacterium lepromatosis. Proc Natl Acad Sci USA 112 ( 14 ) : 4459 - 4464 Jump up ^ Schuenemann VJ, Singh P, Mendum TA, Krause - Kyora B, Jager G, et al. ( 2013 ) Genome - wide comparison of medieval and modern Mycobacterium leprae. Science 341 : 179 -- 183 Jump up ^ Djelouadji Z, Raoult D, Drancourt M ( 2011 ) Palaeogenomics of Mycobacterium tuberculosis : epidemic bursts with a degrading genome. Lancet Infect Dis 11 ( 8 ) : 641 - 650 Jump up ^ Monot M, Honoré N, Garnier T, Araoz R, Coppée JY, Lacroix C, Sow S, Spencer JS, Truman RW, Williams DL, Gelber R, Virmond M, Flageul B, Cho SN, Ji B, Paniz - Mondolfi A, Convit J, Young S, Fine PE, Rasolofo V, Brennan PJ, Cole ST ( 2005 ) On the origin of leprosy. Science 308 ( 5724 ) : 1040 - 1042 Jump up ^ `` Leprosy : MedlinePlus Medical Encyclopedia ''. www.nlm.nih.gov. Retrieved 2015 - 11 - 17. Jump up ^ Duthie MS, Gillis TP, Reed SG ; Gillis ; Reed ( November 2011 ). `` Advances and hurdles on the way toward a leprosy vaccine ''. Hum Vaccin. 7 ( 11 ) : 1172 -- 83. doi : 10.4161 / hv. 7.11. 16848. PMC 3323495. PMID 22048122. CS1 maint : Multiple names : authors list ( link ) Jump up ^ `` Zoonotic Leprosy in the Southeastern United States ''. www.cdc.gov. External links The genome of Mycobacterium leprae `` Mycobacterium leprae ''. NCBI Taxonomy Browser. 1769. Gram - positive bacterial infection : Actinobacteria ( primarily A00 -- A79, 001 -- 041, 080 -- 109 ) Actinomycineae Actinomycetaceae Actinomyces israelii Actinomycosis Cutaneous actinomycosis Tropheryma whipplei Whipple 's disease Arcanobacterium haemolyticum Arcanobacterium haemolyticum infection Actinomyces gerencseriae Propionibacteriaceae Propionibacterium acnes Corynebacterineae Mycobacteriaceae M. tuberculosis / M. bovis Tuberculosis : Ghon focus / Ghon 's complex Pott disease brain Meningitis Rich focus Tuberculous lymphadenitis Tuberculous cervical lymphadenitis cutaneous Scrofuloderma Erythema induratum Lupus vulgaris Prosector 's wart Tuberculosis cutis orificialis Tuberculous cellulitis Tuberculous gumma Lichen scrofulosorum Tuberculid Papulonecrotic tuberculid Primary inoculation tuberculosis Miliary Tuberculous pericarditis Urogenital tuberculosis Multi-drug - resistant tuberculosis Extensively drug - resistant tuberculosis M. leprae Leprosy : Tuberculoid leprosy Borderline tuberculoid leprosy Borderline leprosy Borderline lepromatous leprosy Lepromatous leprosy Histoid leprosy Nontuberculous R1 : M. kansasii M. marinum Aquarium granuloma R2 : M. gordonae R3 : M. avium complex / Mycobacterium avium / Mycobacterium intracellulare / MAP MAI infection M. ulcerans Buruli ulcer M. haemophilum R4 / RG : M. fortuitum M. chelonae M. abscessus Nocardiaceae Nocardia asteroides / Nocardia brasiliensis Nocardiosis Rhodococcus equi Corynebacteriaceae Corynebacterium diphtheriae Diphtheria Corynebacterium minutissimum Erythrasma Corynebacterium jeikeium Group JK corynebacterium sepsis Bifidobacteriaceae Gardnerella vaginalis Retrieved from `` https://en.wikipedia.org/w/index.php?title=Mycobacterium_leprae&oldid=818079922 '' Categories : Acid fast bacilli Leprosy Mycobacteria Bacteria described in 1874 Hidden categories : CS1 Norwegian - language sources ( no ) CS1 maint : Multiple names : authors list Articles with ' species ' microformats All pages needing factual verification Wikipedia articles needing factual verification from July 2009 Talk Contents About Wikipedia Wikispecies বাংলা Беларуская Català Čeština Deutsch Eesti Español Euskara فارسی Français Galego 한국어 Bahasa Indonesia Íslenska Italiano עברית Latina Bahasa Melayu Nederlands 日本 語 Norsk Norsk nynorsk Occitan Polski Português Română Русский Simple English Slovenščina தமிழ் Türkçe Українська Tiếng Việt 中文 Edit links This page was last edited on 1 January 2018, at 12 : 06. 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Question: where is mycobacterium leprae most likely to be found
Answer: warm tropical countries