The simultaneous inoculation of Mycobacterium leprae and M. intracellulare into nude mice: development of cutaneous leproma and accelleration of foot pad swelling.

Organisms of the non-pathogenic Mycobacterium intracellulare serotype 19 Darden enhanced the pathogenicity of M. leprae when inoculated together into the foot pads of nude mice. This supporting effect could be demonstrated by an accelleration of foot pad swelling, beginning 4 months after inoculation and by the development of cutaneous leproma on dorsal and lateral body sites within 6 months after inoculation. These leproma increased in number and size during the 9 months they were under observation and demonstrated micromorphological characteristics similar to those of human leprosy.