Associated with Bacterial toxins damage major organs, resulting in a high death rate, Toxigenic strains are infected with a bacteriophage that contains the gene for the diphtheria toxin
Gram stain - can be pleomorphic, "picket fence", or "Chinese letters"
Staining with methylene blue will reveal metachromatic granules, which are red to purple intracellular granules
Urease - NEG
Pyrazidamidase - NEG
Nitrate - POS
Catalase - POS
Elek test (uses anti-toxin to detect the toxin)