Local reactivity, local resistance and systemic dissemination in Mycobacterium lepraemurium (MLM) infection

Local reactivity measured as swelling of the infected footpad, local resistance to bacterial multiplication, and capacity to limit systemic dissemination were studied in C57BL, C3H/Bom, C3H/HeJ, and A/Sn mice inoculated with Mycobacterium lepraemurium. C57BL mice developed a strong local reaction with a sudden onset, and effectively limited local multiplication as well as systemic dissemination of bacteria to the liver and spleen as determined 19 weeks after the inoculation. C3H/Bom mice showed no local reaction, had high numbers of bacteria locally, and had extensive systemic dissemination of the infection. C3H/HeJ mice, on the other hand, developed a small local reaction and had less systemic dissemination of bacteria than C3H/Bom mice. In C57BL mice and in the two C3H substrains local reactivity, local resistance to infection, and resistance to systemic spread of the infection paralleled each other. In contrast, A/Sn mice showed a small local reaction, had the most extensive bacterial multiplication at the site of inoculation of the four mouse strains tested, and at the same time were the mice that most effectively restricted systemic dissemination of the infection. Thus, the mechanisms restricting local bacterial multiplication may be different from the mechanisms limiting bacterial dissemination. Neither bacterial growth locally at the site of subcutaneous inoculation in the footpad, nor systemic dissemination of the infection, followed a mouse strain pattern consistent with the Ity/Lsh/Bcg gene model. In experimental mycobacterial infection both local bacterial growth at the site of inoculation and systemic dissemination should be determined.