Hepatic lesions and bacterial changes in mice during infection of Fusobacterium necrophorum.

Liver abscesses were induced in male albino mice within 1 week after intraperitoneal inoculation of viable Fusobacterium necrophorum LA19 culture. Fusobacteremia was transitory and reached a peak 2 h after inoculation then sharply declined until its disappearance 24 h post inoculation. By contrast, the number of fusobacteria in the liver increased rapidly during the first 4 h post inoculation and continued to do so less rapidly until the last sampling time (48 h post inoculation). There were small or large areas of necrosis, usually surrounded by inflammatory cells, small focal accumulations of lymphocytes, plasma cells, and macrophages in areas of parenchyma with no degenerations, generalized proliferation of Kupffer cells, and a few accumulations of fibrin and leukocytes on the surface. Ultrathin sections of infected liver tissues reveled both intact and partially degraded F. necrophorum cells enclosed in phagocytic and digestive vacuoles of mononuclear cells, The results indicate that macrophages play a key role in the pathogenesis of liver abscesses.