Tellurite Blood Agar is a selective medium used for isolation and cultivation of Corynebacterium species.
Potassium tellurite acts as a selective agent and has inhibitory activity against most gram-positive and gram-negative bacteria except Corynebacterium species.
C.diphtheriae reduces potassium tellurite to tellurium and thereby produce gray-black coloured colonies.
Corynebacterium diphtheriae on tellurite agar
Reference :
http://www.microbeworld.org
