Abstract
As stated in the previous report, all kinds of killed vaccine were found to heveno prophylactic effect, so that studies were made on the manufacture of live vaccine and in this connection efforts were made to produce a variant of Listeria monocytogenes without pathogenicity.
1. Acriflavine resistance of listeria strains was from 0.05% to 0.07%. Cultures were made, therefore, first on the liver infusion agar medium containing the growth limit concentration of acriflavine as stated above. In the successive cultures, the concentration of acriflavine was increasedd gradually up to the maximum of 0.3% which was the maximum tolerable concentration.
2. Strains with this maximum tolerable acriflavine concentration had already lost their fermentation ability on lactose, dextrin, and saccharose which was possessed by the original strain.
3. As for their mouse pathogenicity, they failed to show any pathogenicity by the subcutaneous inoculation or lip scarification. But they still exhibited pathogenicity when inoculated intra peritoneally or intracerebrally.
4. On histolagical examination, the lesions produced were extremely mild. Thus. it was confirmed that the pathogenicity is attenuated in those acriflavine resistant strains.
