COMPARISON OF THE RESISTANCE OF C57BL 6 AND C3H/HE MICE TO INFECTION WITH MYCOBACTERIUM-PARATUBERCULOSIS/

Susceptibility of C57BL/6 (Bcg(s)) and C3H/HeN (Bcg(r)) mice to an int rapenitoneal infection with Mycobacterium paratuberculosis strain 1969 8 was compared (by histopathology and the number of mycobacteria isola ted from the spleen). Mycobacterial counts from the spleen of Bcg(r) m ice progressively decreased over the course of infection but remained unchanged in Bcg(s) mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcg(s) mice , whereas lesions were transient or absent in Bcg(r) mice. These resul ts indicate that Bcg(r) mice are inherently resistant to M. paratuberc ulosis, whereas Bcg(r) mice are inherently susceptible. These differen ces may prove useful in elucidating the mechanisms of resistance and s usceptibility to paratuberculosis and other mycobacterial infections.