Some aspects of murine experimental listeriosis.

A set of experiments was carried out in order to approach the complex nature of L. monocytogenes infections from different aspects. Experiment 1 showed that Listeria are able to gain admission to body by numerous ways and both subcutaneous and oral entry can lead to fatal septicemia. It also gave slight support to the theory of direct neural transmission of Listeria to the brain and indicated the possibility that intestinal absorption after oral exposition at least partly occurs via lymphatic vessels. No inflammatory reaction could be caused to mice by ocular flushing with Listeria suspension. The second trial proved that there are vast differences in the animal pathogenecity of Listeria strains — even among those of the same serotype. In experiment 3A the abolishing effect of dextran sulfate on the early resistance of mice to Listeria was confirmed and it turned out that cortisone at a therapeutic dose level did not bring about that phenomenon. Levamisole granted no conspicuous enhancement of resistance in this acute challenge; however, the results of the immunity test (3B) suggested that levamisole may be beneficial during the induction phase. On the other hand, starvation appeared to impair long-term immunity. Likewise, in experiment 4 starved mice were quite susceptible to acute challenge with Listeria. Raised ambient temperature, on the contrary, prominently increased the survival rate of the animals. Owing to the fairly small number of animals these results should be regarded as preliminary starting points to further studies.