Importance of the footpad lesion in the mouse response to local inoculation of Mycobacterium marinum.

The importance of the footpad lesion was studied in CBA mice inoculated in the hind footpad with viable or heat-killed Mycobacterium marinum Popliteal or popliteal and inguinal lymphadenectomy was followed by modest enhancement of the process only when node excision was carried out 6 days after inoculation of a small number of viable organisms. Following inoculation in the footpad of a large number of heat-killed organisms, only 10% of the inoculum was recovered from the site of inoculation, only 0.1% from the popliteal node and even less from the inguinal node and spleen. Despite the small proportion of inoculated M. marinum remaining in the footpad, amputation of the inoculated foot as early as 4 days after inoculation abrogated the protective effects of the inoculation, whereas amputation performed 7 days after inoculation was without effect.