Mycobacterium leprae, also known as Hansen’s coccus spirilly, mostly found in warm tropical countries, is a bacterium that causes leprosy (Hansen's disease). It is an intracellular, pleomorphic, acid-fast 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 fuscin rather than with the traditional Gram stain. The culture takes several weeks to mature.

Mycobacterium leprae, 1869 durch den Norweger Gerhard Armauer Hansen entdeckt, ist der Erreger der Lepra (Aussatz), an der in den Tropen immer noch sehr viele Menschen erkrankt sind.

Mycobacterium leprae (ou bacille de Hansen) est la bactérie responsable de la lèpre chez l'homme (et le tatou).

Lepra eller spetälska eller Hansens sjukdom är en infektionssjukdom orsakad av bakterien Mycobacterium leprae. Man räknar med att det finns cirka 10 miljoner leprasjuka i världen, främst i tropiska länder med låg utvecklingsnivå.

Il Mycobacterium leprae (conosciuto anche come Bacillo di Hansen), è l'agente eziologico della lebbra. Il bacillo fu scoperto dal dottor Gerhard Armeuer Hansen in Norvegia nel 1873.