Separation of M. leprae from human leproma and the development of a cytoplasmic skin test antigen from purified bacilli.

A successful method for purification of M. leprae from human leproma without subjection to heat has been developed. The "floater" phenomenon has been described which consists of bacillary tendency to float in the supernate when bacilli which are not autoclaved are separated from tissues by enzymatic digestion. A method for preparing cytoplasmic fractions from purified M. leprae has been developed for the production of a skin test antigen for leprosy. The cytoplasmic fraction of M. leprae elicited positive skin test responses in people with tuberculoid leprosy and negative responses in lepromatous leprosy. Cytoplasmic preparations from purified M. leprae had little cross-reactive relationship with the organism BCG. The small particulate fraction elicited positive reactions in PPD-S negative as well as BCG vaccinated individuals.