This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'True statement about diphtheria toxin is \nSelect and explain. \nA. Toxin is phage mediated, B. Toxin is required for local infection, C. Endotoxaemia causes systemic manifestation, D. Toxin acts by inhibiting synthesis of capsule', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Toxigenicity of the diphtheria bacilli depends on the presence in it of corynephages which acts as the genetic determinant controlling toxin production. The diphtheria toxin acts by inhibiting protein synthesis. Specifically, a fragment B heparin binding and fragment A inhibits polypeptide chain elongation in the presence of nicotinamide adenine dinucleotide by inactivating the elongation factor EF-2. Reference: Textbook of Microbiology; Anathanarayan and panicker&;s; 9th edition; Page no: 238', 'role': 'assistant'}]