In a completely and adequately immunized child against diphtheria, the throat swab was collected. It showed the presence of C.diphtheriae organisms on Albert staining. These organisms can have one of the following properties on further processing:
This child is carrier of diphtheria.

Postassium tellurite is selective media for isolation of diphtheria bacillus from convalescent contact carriers.
Other three test are done for testing virulence, only when isolated strain is C.diphtheria.
It can grow on potassium tellurite media
It would show +ve Elek’s gel precipitation test
It can be pathogenic to experimental guinea pig
It can produce cytotoxicity in tissue culture