Type species of the genus, and the causative organism of diphtheria, C. diphtheriae excretes a powerful exotoxin. Three types—mitis, intermedius and gravis-occur, differentiated as described under Corynebacteria. Subtypes of each type have been classified by the use of agglutinating sera. The exotoxin produced by all types of C diphtheriae is identical, and antitoxin is produced by immunization of horses with successive doses of diphtheria toxoid and toxin.
The causative agent of diphtheria in humans.