Hoyle's agar
Hoyle's agar is a selective medium that uses tellurite to differentially select Corynebacterium diphtheriae from other upper respiratory tract flora. The medium appears cream to yellow colored, and takes the form of a free-floating powder. It is a modification of Neill's medium.
Hoyle's tellurite agar contains:
| Proteose peptone | 10 g/L |
| Beef extract | 10 g/L |
| Sodium chloride | 5 g/L |
| Blood, laked | |
| Tellurite | 0.35 g/L |
| Agar | 15 g/L |
The medium inhibits growth of Gram-negative bacteria and many Gram-positive bacteria, and reduction of the tellurite is characteristic of corynebacteria Microscopic examination of samples of suspected colonies, using Neisser differential staining, is required for confirmation.