[Cytopathogenic effect of diphtheria exotoxin in cultured chick embryo fibroblasts]

Abstract

One hundred fifty strains of Corynebacterium diphtheriae were studied from patients with symptoms of diphtheria and from healthy persons. 136 strains (90.67%) belonged to the mitis biotype, 12 (8.0%) and 2 (1.33%) to gravis and intermedius biotypes respectively. Toxigenicity was determined by traditional in vivo methods with rabbits and plaque immunodiffusion in KL-virulence medium. From the 136 mitis biotype strains studied, 130 (95.58%) showed positive toxigenicity by both methods and 11 strains (91.66%) from gravis biotype and 2 (100%) of intermedius biotype gave same results. The cellular cytotoxicity of the diphtheriae toxin was tested on culture of chicken embryo fibroblast and were positive in 132 (97.05%) strains of mitis biotype, and in all strains of gravis and intermedius biotypes. These results suggest that the cytotoxicity test seems to be a more sensitive method for detecting diphtheriae toxin production.