Bacterium
Mycobacterium leprae
Acid-fast leprosy bacillus (cannot be cultured)
my-koh-bak-TEER-ee-um LEP-ray
High-yield clue
Cannot be grown on artificial media, prefers cooler skin and peripheral nerves, and is studied in armadillos; disease spans tuberculoid (paucibacillary) to lepromatous (multibacillary).
Overview
An acid-fast, obligate intracellular bacillus that causes Hansen disease (leprosy). It is the classic teaching organism that cannot be grown on artificial laboratory media.
Classification
- Acid-fast bacillus
- Obligate intracellular
- Aerobic
- Slow-growing
- Non-culturable in vitro
Lab & identification clues
- Acid-fast staining
- Cannot culture on artificial media
- Armadillo / mouse footpad research models
- Prefers cooler body temperatures
Associations
- Hansen disease (leprosy)
- Tuberculoid (paucibacillary) vs lepromatous (multibacillary) spectrum
- Peripheral nerve involvement with loss of sensation
Commonly confused with
- Mycobacterium tuberculosis
- Nontuberculous mycobacteria
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.