noun
Mycobacterium leprae; leprosy bacillus
Scientific/medical term for the bacterium that causes leprosy (Hansen's disease).
らい菌は、1873年にアルマウェル・ハンセンによって発見された。
Mycobacterium leprae was discovered by Armauer Hansen in 1873.
Standard modern spelling using the hiragana らい for the leprosy part.
Older kanji spelling using 癩 (leprosy). The kanji 癩 is not a jōyō kanji and may be unfamiliar to many readers.
Compound of らい (leprosy, from Middle Chinese 癩) and 菌 (bacterium, from Middle Chinese 菌).