Studies on the Action of Penicillin. IV. Development of Penicillin Resistance by Gonococcus.

Penicillin-fastness developed most rapidly in gonococci under conditions which permitted the greatest number of viable microorganisms to be transferred to a higher concentration of penicillin at each transfer. One strain of gonococcus acquired the ability to prow on media containing 21 units per ml. So appreciable increase in penicillin tolerance resulted from repeated exposure to bacteriostatic concentrations of penicillin.