Abstract
Conclusions
Two strains of group A streptococci failed to acquire resistance to penicillin after repeated exposures to sublethal amounts either in embryonated hens’ eggs or in mice. With 2 strains each of group B and C organisms, however, in eggs there was a definite increase in penicillin resistance. In mice this same increase may have occurred, but we failed to demonstrate it through limitations of the method. The increasing penicillin resistance in vivo of the group B and C streptococci was not associated with increasing resistance in vitro.
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