Mycobacterium leprae
species of bacterium; form of leprosy
Mycobacterium leprae (also known as the leprosy bacillus or Hansen's bacillus) is one
of the two species of bacteria that cause Hansen's disease (leprosy), a chronic but curable infectious disease that damages the peripheral nerves and targets the skin, eyes, nose, and muscles.
It is an acid-fast, Gram-positive, rod shaped bacterium and an obligate intracellular parasite, which means, unlike its relative Mycobacterium tuberculosis, it cannot be grown in cell-free laboratory media. This is likely due to gene deletion and decay that the genome of the species has experienced via reductive evolution, which has caused the bacterium to depend heavily on its host for nutrients and metabolic intermediates. It has a narrow host range and apart from humans, the only other natural hosts are nine-banded armadillo and red squirrels.
The bacteria infect mainly macrophages and Schwann cells, and are typically found congregated as a palisade.
Mycobacterium leprae was sensitive to dapsone as a treatment alone, but since the 1960s, it has developed resistance against this antibiotic. Currently, a multidrug treatment (MDT) is recommended by the World Health Organization, including dapsone, rifampicin, and clofazimine. The species was discovered in 1873 by the Norwegian physician Gerhard Armauer Hansen, and was the first bacterium to be identified as a cause of disease in humans.
Microbiology
Mycobacterium leprae is an intracellular, pleomorphic, non-sporing, non-motile, acid-fast, pathogenic bacterium. It is an aerobic bacillus (rod-shaped bacterium) with parallel sides and round ends, surrounded by the characteristic waxy coating of mycolic acid unique to mycobacteria.
The public source identifies “Mycobacterium leprae” as species of bacterium; form of leprosy. This brief keeps that definition visible, then builds a research path around Mycobacterium, leprae and species.
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A short description can identify a subject without explaining its stakes. For “Mycobacterium leprae”, the useful work is to connect “species of bacterium; form of leprosy” to the records capable of establishing context and consequence.
The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Aug 11, 2026. The linked authority identifier is Q155891. The Library of Congress control number is sh88023290. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 1873.
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This entry incorporates text from “Mycobacterium leprae” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.