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
Staphylococcus aureus causes vomiting in 16-18 hours. The mechanism of action is by 
Select and explain. 
A. Stimulation of cyclic AMP, B. Vagal stimulation, C. Stimulation of Cyclic GMP, D. Acts through ganglioside GM receptor
B: Vagal stimulation
Answer: B: Vagal stimulation 
Explanation: It has been suggested that SEs(staph enterotoxins) stimulate the vagus nerve in the abdominal viscera, which transmits the signal to the vomiting centre in the brain. Enterotoxin is responsible for the manifestations of staph food poisoning - nausea, vomiting, and diarrhoea 2-6 hr after consuming food contaminated with enterotoxin.
The toxin directly acts on ANS to cause the illness rather than on the gastrointestinal mucosa.