Toby is a 16 year-old, pimple-faced boy, who has been working after school at a local pizzeria trying to make a little money for his new guitar. 2 days ago, Toby was working in the kitchen, shredding pounds and pounds of cheese for pizza. The cheese was used to prepare pizzas for many customers.
Today, the pizzeria got many phone calls with complaints from customers experiencing nausea, vomiting, and diarrhea, blaming their symptoms on the pizza they ate yesterday.

Explain, what could have happened here. Which bacteria do you think, caused these symptoms, how, and why?