<prompt> 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:It can grow on potassium tellurite mediaIt would show ve Eleks gel precipitation testIt can be pathogenic to experimental guinea pigIt can produce cytotoxicity in tissue culture  <response>: 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. 