THE BCG-INDUCED RESISTANCE TO LISTERIOSIS

BCG immunization schedules for the demonstration of resistance to listeriosis in C3H mice were re-evaluated in a series of experiments. A two-step procedure was found to be superior to a one-step vaccination schedule. Reactivation with BCG five days before challenge caused a significant depression of the multiplication of Listeria monocytogenes in the spleen. A saline extract of tubercle bacilli was able to reactivate the BCG immunization in the “same way, even though a transient non-immunogenic effect of the same extract was also demonstrated. In the two-step procedure the vaccination dose was found to play a minor role, whereas the reactivation was dose-dependent.