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': 'Which is the principal virulence factor in Clostridium tetani \nSelect and explain. \nA. Tetanolysin, B. Tetanospasmin, C. Tetanotactin, D. Immobility factor', 'role': 'user'}, {'content': "Answer: B \nExplanation: C.tetani produces two distinct toxins- a hemolysin(tetanolysin), and neurotoxin(tetanospasmin). Tetanospasmin: This is the toxin responsible for tetanus. This toxin acts pre-synaptically. The abolition of spinal inhibition causes an uncontrolled spread of impulses initiated anywhere in the central nervous system. This results in muscle rigidity and spasms. Tetanolysin: it is not relevant in the pathogenesis of tetanus. Ref: Textbook of microbiology; Ananthanarayan and paniker's; 10th Edition; Pg: 265", 'role': 'assistant'}]