True about corynebacterium diphtheria includes all of the following except:: (A) Deep invasion is not seen, (B) Elek's test is done for toxigenicity, (C) Metachromatic granules are seen, (D) Toxigenicity is mediated by chromosomal change
Answer is D. Ans. (d) Toxigenicity is mediated by chromosomal change "Corynebacteriophage beta carries the structural gene (tox+) encoding diphtheria toxin and a family of closely related corynebacteriophage are responsible for toxigenic conversion of tox- C.diphtheria to tox+ phenotype." Elek's gel precipitation test is in vitro test for toxin detection.