STUDY OF THE INVOLVEMENT OF THE SCIATIC-NERVE FOLLOWING INOCULATION WITH MYCOBACTERIUM-LEPRAE AND OTHER MYCOBACTERIA IN THE MOUSE FOOT PAD

  • 1 January 1984
    • journal article
    • research article
    • Vol. 52  (4) , 506-514
Abstract
In order to determine whether M. laprae 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 post-inoculation 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 mo., 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 its 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 mo., 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 mo.) 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. The study reveals that M. leprae inoculated into the foot pad of the mouse produce certain typical changes in the sciatic nerve which were not previously demonstrated with any of the other human pathogenic or non-pathogenic mycobacteria used in this study. Only 3 strains of mycobacteria cultivated from biopsies of leprosy patients, namely, FMR strains No. 51 and No. 75 and ICRC, demonstrated changes typical of those produced by M. laprae. In view of the fact that the peripheral nerve and its Schwann cells is the large of M. leprae, the typical changes seen in the sciatic nerve of the mouse model may be used as one of the criteria for characterizing any cultivable organism claiming to be M. laprae.