This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': "Elek's gel precipitation test is done for: \nSelect and explain. \nA. Corynebacterium diphtheria, B. Salmonella choleraesuis, C. Clostridium botulinum, D. Diphtheroids", 'role': 'user'}, {'content': "Answer: A \nExplanation: Elek's gel precipitation test is done for Corynebacterium diphtheriae. Detection of C. diphtheriae: Elek's gel precipitation test - Double diffusion in two dimensions (Ouchterlony procedure), Detection of tox gene by PCR. Detection of diphtheria toxin by ELISA or immunochromatographic test (ICT). Cytotoxicity produced on cell lines.", 'role': 'assistant'}]