This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
True about cornebacterium diphtheriae is all except? 
Select and explain. 
A. Deep invasion is not seen, B. Eleks test is done for toxigenicity, C. Metachromatic granules are seen, D. Toxigenicity is mediated by chromosomal change
D: Toxigenicity is mediated by chromosomal change
Answer: D: Toxigenicity is mediated by chromosomal change 
Explanation: Ans. is 'd' i.e., Toxigenicity is mediated by chromosomal change . This has been asked so many times in most of the examinations :? . Toxigenicity of diphtheria is not due to chromosomal change, it is phase mediated. About other options . Diphtheria is a toxemia, the bacilli remain confined to the site of entry, where they multiply and form toxin. . Elek's gel precipitation test is an in vitro test for toxigenicity. . Metachromatic granules (volutin or babes Ernest granules) are seen.