Abstract
Penicillin induced variants were obtained from highly virulent B, anthracis strains 52 and Shikan as well as from weakly virulent H strain (Pasteur II) . Tests were made on their toxicity, biological and immunological characters, and at the same time, various studies were made on their reverse variaion. Stated in the follwing are the results obtained thereof:
1. It took successive transplantation for 115 generations on the medium containing penicillin before obtaining the resistance of 20 u/ml.
2. The strains which and acquired penicillin resistance showed either attenuation or loss of their virulence regardless to the virulence of starting strain.
3. Penicillin resistant strains lost their capsule and showed remarkable weakening in their spore forming ability. And at the same time, they lost caseinase activity.
4. This penicillin resistance was highly unstable and they reversed easily to the sensitive straints. But the changes accompanying the acquisition of penicillin resistance stated above were stable for a long period of time.
5. Vaccination of so-called Sterne's saponin-spore suspension prepared by the use of penicillin resistant strain could prevent the death of the guinea pigs, rabbits and goats received the lethal dose of highly virulent strain.
6. Above mentioned live vaccine prepared by the of penicillin resistant strain demonstrated virulence lower than Pasaeur I and accordingly, the loss of vaccination was much smaller. Whereas, its immunizing effect was much larger than that of Pasteur II vaccine and the inoculation of much smaller amount was sufficient for the production of immunity.
