Bacteremia in Experimental Tyzzer's Disease of Mice

Bacteremia was observed during the late stage of experimental Tyzzer's disease in mice. The number of organisms in the blood in mice treated with cortisone increased markedly in the infection with highly virulent organisms, whereas bacteremia was of low incidence and less severe in infections with low virulence organisms. The number of organisms in the blood stream was shown to increase linearly during the course of fatal infection attaining a maximum level of 10⁷ organisms per ml blood. The number of organisms in the blood was found to be closely related to the number in the liver when bacteremia was observed. In the peripheral blood, organisms were first detectable when the number of organisms in the liver gained a level of 10⁷ per g tissue, and the subsequent increase in the number of bacteria in the blood was approximately 3 times more rapid than in the liver. The organisms in the blood were comparable to those in the liver morphologically as well as in pathogenicity. Histopathological examination frequently revealed liberation of organisms from liver cells into sinusoids. There was no evidence of significant multiplication of the organisms in organs other than the liver.