Proof for the lack of diphtheria toxin in culture filtrates of Corynebacterium ulcerans strain ATCC 9015.

Extensive efforts to identify the diphtheria toxin in culture filtrates of C. ulcerans strain ATCC 9015 was unsuccessful. The culture filtrates did contain a component (called D-antigen) which formed a precipitin line with commercial diphtheria antitoxin. This component was purified by immunosorbent techniques using immobilized preparations of diphtheria antitoxin. It was shown, that D-antigen has a molecular weight of 84000, is not toxic for guinea-pigs, and has nothing in common with purified diphtheria toxin when tested in gel-diffusion tests. The lack of diphtheria toxin in form of its fragments in culture filtrates concentrated 20-fold was proved by the highly sensitive and specific viroimmunoassay.