Salmonellosis in mice infected with Mycobacterium tuberculosis BCG. I. Role of endotoxin in infection.

In agreement with previous observations, mice dying of salmonellosis were found to have a relatively constant number of Salmonella cells in their carcasses (ca. 5 x 10(9)). This number was not the result of bacterial overgrowth in moribund animals and therefore appears to be related to lethality. Similar numbers of salmonellae were recovered from the carcasses of infected mice which had previously been rendered hyperreactive to endotoxin either by infection with M. tuberculosis BCG or by adrenalectomy. In BCG mice, desensitization to endotoxin did not occur during the infection and, therefore, at death these mice contained a number of bacteria which would be equivalent to 1,000 ld(50) of endotoxin. Although the number of bacteria recovered from normal mice is roughly equivalent to a lethal quantity of endotoxin, this is obviously not the case in hyperreactive mice. Therefore, the relationship between lethality and 5 x 10(9) salmonellae cannot be explained by their endotoxin content. Nevertheless, when hyperreactive BCG mice are challenged parenterally with Salmonella, the endotoxin content of the inoculum may markedly influence the course of the infection.