In 1873, the Norwegian public medical officer Gerhard Henrik Armauer Hansen (1841-1912) identified the leprosy agent, the Mycobacterium Leprae, in a microscopic picture. The Breslavian dermatologist Albert Neisser (1855-1916) succeeded in reliably proving the agent in  the year 1879 by means of a colouring method.

Gerhard Henrik Armauer Hansen
Gerhard Henrik Armauer Hansen
Albert Neisser
Albert Neisser

 

The Mycobacterium Leprae is gram-positive, acid-fast and has – compared to other bacteria - the longest period of generation with up to 15 days. The period of regeneration takes only place on an intra-cellular basis, mainly in the Makrophagen of the skin and in the Schwann-cells of peripheral nerves, and almost exclusively in the human body. The reproduction of the Mycobacterium Leprae outside the human body has been achieved in the  "mouse plantar model" and in the nine-banded armadillo. The development of an effective vaccine against leprosy has also proved to be unsuccessful owing to the fact that the armadillo cannot survive in captive breeding. Only very small quantities of the bacteria in an artificial nutrient solution can be produced thus representing a considerable obstacle in research.

The material necessary for the microscopic examination of the agent is obtained by means of the scarification test. The Mycobacterium Leprae can be proved in three different forms:

 

  • as a massive rod
  • as fragmented rod
  • granulomatous

These morphologic terms of the bacteria are called MI (morphological index) and repeated tests lead to a statement concerning the process of leprosy. The number of bacteria is analyzed according to the semi-quantitative logarithmic method of Ridley, in which the density of bacteria is categorised on a scale from 0 to 6+. This is called the bacteriological index (BI).

 

Mycobacterium leprae
Mycobacterium leprae

 

These microscopic picture from the “Institute for Medical History” were photographed by courtesy of the Heinrich-Heine University in Düsseldorf, Germany.