Toxin Production by C. diphtheriae Types

Conclusions

The Park 8 strains are the only potent toxin producers from the gravis, intermedius, mitis and Park 8 strains tested. All strains were virulent, the Park 8 and Freeman strains but feebly so. The cultural requirements of the Park 8 strains for optimum toxin production vary with the strain in its iron and tryptophan requirements. The same is true for the intermedius strain “Shore”, whose toxigenic capacity is also increased by the addition of isoleucine.

Whilst all markedly pathogenic strains of C. diphtheriae tested were poor toxin producers under the experimental methods applied, there is indication that optimum conditions may not have existed for toxin production by these strains.