Mycobacterium leprae
Chelsea Winkelman

Mycobacterium leprae are the bacteria that cause leprosy, a skin disease.  Leprosy has been around for a very long time; it was a common ailment in the bible. It is characterized by skin sores and nerve damage, with a tendency to get progressively worse without treatment.  Some symptoms of leprosy include lesions on the skin, numbness in the extremities, and muscle weakness.  It is easily treatable with certain antibiotics, however new drug resistant strains have been witnessed.  For over fifty years Dapsone has been used to effectively treat a Mycobacterium leprae infection.  However, with the emergence of these new drug resistant forms, multidrug therapy, usually consisting o f Rifampicin, Clofazamine, and Dapsone, is the commonly accepted treatment method.  This helps lessen the chance of development of resistance genes.  Leprosy has two common forms:  tuberculoid and lepromatous.  They both have similar symptoms, however the lepromatous is much more severe, forming large disfiguring lumps on the body. 

The microorganism responsible for this disease, Mycobacterium leprae, is a gram-positive, rod-shaped bacteria with a thick waxy coating.  Due to this coating, it cannot be stained with the regular gram method and instead is stained with carbolfuschin.  It also has a long incubation period, meaning that it may be a long time before symptoms appear, as long as twenty years in some cases.  This makes it difficult to determine when the disease was contracted.  Early diagnosis is important in order to limit damage.  The presence of Mycobacterium leprae can be diagnosed by a biopsy of the lesions or skin scraping examination.  A Lepromin skin test can be performed in order to differentiate between lepromatous and tuberculoid leprosy. 

Mycobacterium leprae was first discovered in 1873 by a Norwegian scientist, Dr. Gerhard Armauer Hansen.  Oddly, it has never been grown in bacterial media or cell culture, but it has been grown in mouse footpads.  Although knowledge of this microorganism has been around since 1873, it still is not completely understood how it is transmitted.  Before the discovery of the Mycobacterium leprae microorganism, many believed that leprosy was hereditary in origin, but now it is widely accepted to be spread by respiratory droplets.  However, this is not wholly supported because over half of the people who are diagnosed with leprosy have had no known contact with an infected person.  The disease doesn’t normally occur in animals either, with the exception of some cases found in feral armadillos and certain primates.  Transfer from animals to humans is unlikely, but has been confirmed in a few cases. 

With the advent of some drug resistant strains of this bacteria and increased numbers of cases, leprosy is again becoming something of a threat.  Approximately 100 cases of leprosy are documented per year in the United States.  In 2002, 763,917 cases were documented worldwide with most of these occurring in Brazil, Madagascar, Mozambique, Tanzania, and Nepal.  Almost twenty percent of Mycobacterium leprae infections occur in children under the age of ten.  In children the cases are split pretty evenly between female and male, however in adults males are twice as likely to contract a Mycobacterium leprae infection as females.

Mycobacterium leprae (leprosy).”  Infectious Disease /  Copyright 2002.  02 August 2003.  17 February 2010.

“Leprosy.”  Google HealthA.D.A.M.  Copyright 2010.  17 February 2010.

Schoenstadt, Arthur M.D.  “Mycobacterium leprae.”  eMed TV.  Copyright 2006 – 2009.  01 November 2008.  17 February 2010.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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