Bacillus Leprae is non-motile, non-flagellate, non-sporogenous, chromogenic, non-liquefying, non-aërogenic, aerobic, and acid resisting. It very closely resembles the tubercle bacillus in size and shape. It stains in very much the same way as the tubercle bacillus, but is not so resistant. Ordinary methods can be employed. It is more easily decolorized, however, by acids. With Gram's method it stains well.

Pathogenesis

This is the organism that produces leprosy in man and monkeys; possibly in some of the lower forms of animals as well. The bacilli are found throughout the tissue lesions, and have been recovered from the blood of leprous individuals.

Cultures

For many years attempts to grow this organism were unsuccessful, but recently bacteria believed to be the true bacilli of leprosy have been grown on artificial media. This is doubted by some investigators. The organisms obtained are acid fast, and in many respects resemble those found in the tissues. Others, however, may be classed among the diphtheroid, on account of their similarity to the Bacillus diphtherial.

According to Duval, the most successful method is as follows: Egg-albumen or human blood-serum is poured into sterile Petri dishes and dried for three hours at 700 C. The excised leprous nodule is then cut into thin slices, which are distributed over the surface of the coagulated albumen. By means of a pipet the medium is bathed in a 1 per cent, sterile solution of trypsin. The Petri dishes are now placed in a moist chamber and incubated for a week or ten days. The bits of tissue soften to a thick, creamy consistence and the bacilli multiply enormously. They may then be transferred to serum-glycerin-agar or to ordinary agar plus 1 per cent, of tryptophan. The colonies on these media are moist and orange colored.

Culture

Ordinary media. In gelatin punctures gas-bub-bles quite frequently appear, but there is no liquefaction of the medium. Gives the so-called "nail growth." Will grow from 160 to 400 C.