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
[{'content': 'Elek test is used for detecting toxins of the following infection: \nSelect and explain. \nA. Influenza, B. Diphtheria, C. Brucellosis, D. Cholera', 'role': 'user'}, {'content': "Answer: B \nExplanation: Elek gel precipitation test is used for detection of Diphtheria toxin. A presumptive C diphtheriae isolate should be subjected to testing for toxigenicity. Such tests are performed only in reference public health laboratories. There are several methods, as follows: The modified Elek method described by the World Health Organization Diphtheria Reference Unit Polymerase chain reaction (PCR)-based methods Enzyme-linked immunosorbent assays Immunochromographic strip assay Ref: Brooks G.F. (2013). Chapter 12. Aerobic Non-Spore-Forming Gram-Positive Bacilli: Corynebacterium, Listeria, Erysipelothrix, Actinomycetes, and Related Pathogens. In G.F. Brooks (Ed), Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.", 'role': 'assistant'}]