FURTHER OBSERVATIONS ON THE CHANGE TO VIRULENCE OF BACTERIOPHAGE-INFECTED AVIRULENT STRAINS OF CORYNEBACTERIUM DIPHTHERIAE

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Abstract
Virulent cultures of C. diphtheriae were produced from avirulent single cell strains by exposure of the avirulent strains to diphtheria bacteriophage. Avirulent strains that were resistant to the bacteriophage failed to yield virulent cultures. An avirulent and a virulent strain of C. diphtheriae both derived from the same phage lysate of an initially avirulent culture were shown to be antigenically homologous by slide agglutination technique. A strain which differed epidemiologically and antigenically from the initial group studied was shown to yield virulent cultures following exposure to the same bacteriophage The absence of toxicity of avirulent cultures subjected to disintegration was demonstrated. Attempts to produce phage-free cultures of a derived virulent culture by growth in phage antiserum were unsuccessful.