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Principle
- Tellurite blood agar base is a selective medium used for the isolation and cultivation of Corynebacterium species. The tellurite blood agar base is composed of peptone, sodium chloride, phosphate buffer, corn starch, and agar.
- The peptone is the source of nitrogen. Corn starch is the source of carbon and energy source and also neutralizes toxic metabolites. Sodium chloride maintains the osmotic balance of the medium. Phosphate act as a buffer.
- Agar is a solidifying agent. The media is fortified with dextrose, tellurite hemoglobin, and vitamin supplements. Haemoglobin and Vitamin supplements stimulate good growth of Corynebacterium.
- The selectivity is enhanced by the presence of inhibitor and differential by means of ability of an organism to reduce potassium tellurite. Potassium tellurite also acts as a selective agent and inhibits most gram-positive and gram-negative bacteria except Corynebacterium species. C. diphtheriae reduces potassium tellurite to tellurium and thereby produces gray-black coloured colonies.
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