This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology Pa 1 (Gram Positive Cocci, Gram Negative Cocci), Subject name: Microbiology
Staph. aureus causes vomiting in 2 hours after eating contaminated milk product . The mechanism of action is - 
Select and explain. 
A. Stimulation of C AMP, B. Vagal stimulation, C. Stimulation of C GMP, D. Acts through ganglioside GM receptor
B: Vagal stimulation
Answer: B: Vagal stimulation 
Explanation: Option 1, 3 Increase in cyclic AMP/GMP-accumulation of sodium chloride in the intestinal lumen- Diarrhea. Option 2 Toxin Stimulates the vagus nerve and vomiting center of brain. Acts directly on the autonomic nervous system rather than on gastrointestinal mucosa. Option 4 Cholera toxin: binds to GM1 ganglioside receptors present on the intestinal epithelium