Culture medium for Corynebacterium diphtheria is

Loeffler's serum slope: diphtheria bacilli grow on this media very rapidly and colonies can be seen in 6-8 hours, long before other bacteria grow. Colonies are the first small, circular white opaque disc but enlarge on continued incubation and may acquire a distinctly yellow tint. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 242