Study of the involvement of the sciatic nerve following inoculation with M. leprae and other mycobacteria in the mouse foot pad.

In order to determine whether Mycobacterium leprae alone produce the typical damage in the sciatic nerves of foot pad inoculated mice as demonstrated earlier, a comparative study was undertaken using various other mycobacteria inoculated into the hind foot pads of normal Swiss white mice. The findings indicate that FMR isolates No. 51 and No. 75 and M. avium showed multiplication in the foot pads of the mice throughout the 4th, 6th or 8th postinoculation months and these infections were associated with neural changes in the sciatic nerves. The type of nerve involvement in the case of M. avium differs from M. leprae in being predominantly an axonal degeneration at the 8th post-inoculation month, that is, degeneration of the complete axon and myelin debris remnants; whereas in M. leprae infection, where segmental demyelination predominates, the axons are intact and it is the Schwann cell that is affected. The neural changes in the case of FMR isolates No. 51 and No. 75 were similar to those seen in mice inoculated with M. leprae obtained directly from human biopsies. Other mycobacteria, HI-75 (Skinsnes) and M. scrofulaceum, showed growth in the foot pad initially which persisted in the case of M. scrofulaceum until the 20th post-inoculation month, but no ultrastructural changes were observed in the sciatic nerves of these mice. In ICRC-inoculated mice, nerve lesions were seen much later (at the 16th post-inoculation month) and the changes were similar to those seen with M. leprae. M. vaccae, M. smegmatis, M. phlei, and M. intracellulare showed almost no growth in the foot pads of the mice, and there were no detectable changes in the sciatic nerves. M. lepraemurium showed growth in the foot pad but no lesions were seen in the sciatic nerve.(ABSTRACT TRUNCATED AT 250 WORDS)