Isolation of Penicillin-Susceptible Mutants from Penicillinase-Producing Strains of M. pyogenes ∗

Abstract

Summary

Twelve of 13 strains of M. pyogenes which produce penicillinase yielded non-penicillinase-producing mutants which were susceptible to penicillin. This apparent spontaneous type of mutation occurs at a high rate of frequency. Cultivation of a strain of this organism at 45° C significantly increased the number of mutants. No evidence of reversibility of the mutation was obtained.