[Antibiotic therapy in the compromised host--presented as a model for listeriosis in the mouse. II. Effect of tetracycline].

The effectiveness of tetracycline therapy on Listeria-infection in compromised host was evaluated in three different murine models. In normal adult mice infected with a tetracycline susceptible strain of Listeria monocytogenes, treatment with this antibiotic caused a reduced rate of multiplication of bacteria. That is, a low bacterial count was found in the spleen. When the macrophage system which in Listeria-infection represents a major defense mechanism was blocked through dextran sulfate 500, treatment with tetracycline was still very effective. In this case, bacterial multiplication has ceased. However, an elimination of the organisms could only be achieved after the macrophage system recovered from its temporary blockade. Secondly, nude athymic mice which are unable to develop cell mediated immunity were used to establish chronic infection with Listeria. Treatment with tetracycline in this instance only reduced bacterial counts moderately. Thirdly, five days old baby mice which are extremely susceptible to Listeria could at least partially be protected with tetracycline therapy against fatal infection.