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The time course and organ penetration of Listeria monocytogenes Scott A #3, serotype 4b, were investigated by oral inoculation of the organisms (107∼108 CFU/ml) into ICR mice. At thirty minutes after inoculation, the organism of <100 CFU/ml was isolated from blood. Population levels of L. monocytogenes in log10 CFU/g( or ml) at 1h after inoculation were 2.44±0.57 in blood, 2.20±0.38 in mediastinal lymph nodes, 1.14±0.36 in liver, 1.41±0.00 in spleen, while no organism was detected from mesenteric lymph nodes. The results suggest that L. monocytogenes is transported, either after phagocytosis by intraperitoneal macrophages or in suspension in the lymph of the ventral thoracic lymphcentrum, to the lymph nodes of the mediastinal lymphocentrum, prior to systemic dissemination. The level of L. monocytogenes at 24 hrs after inoculation increased to 4.51±0.44, 5.52±0.31, 4.48±0.52, 5.01±0.31 and 2.94±0.37 log10 CFU in blood, mediastinal lymph nodes, liver, spleen and mesenteric lymph nodes, respectively. When tested to know the organs for bacterial infection using such parenchymal organs as blood, liver, spleen and brain, L. monocytogenes was isolated exclusiverly from all liver and spleen samples of six mice 1 day after inoculation. The organism was isolated from the same organs of all experimental animals 3 days after inoculation, whereas the numbers of infected mouse were diminished 7 days after inoculation.
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