The relative effectiveness of pure penicillins against Bacillus anthracis in vitro and in vivo.

The relative activities of penicillins commercial, F, G, K, and X are 38, 52, 100, 29 and 160, respectively, against Bacillus anthracis in vitro. The relative effectiveness of these same penicillins in protecting mice against experimental anthrax is 100, 80, 100, 40 and 107. The effectiveness of penicillin K against anthrax in mice is greater than its reported effect against streptococcal and pneumococcal infections in mice. The penicillins of choice in the treatment of anthrax are penicillins X, G and F as indicated by these experiments on mice. In general, these results agree with those obtained by other workers on streptococcal and pneumococcal infections in mice and syphilis and gonorrhea in man.