Bacterial contamination occurs when:
raw food is not handled correctly
cooked food is mishandled
raw food is prepared incorrectly
cooked food is reheated

Contamination by bacteria occurs because of improper handling of raw food.

Explanation:

Raw foods get easily contaminated if they are kept in a bacterial affected place or are not handled properly. Improper handling means- keeping the food in contact with bacteria affected place or food, unclean chopping board, knife etc.

It is also considered as cross contamination. In this contamination the bacteria gets transported from raw food to other food or a person’s body. It causes food poisoning that leads to illness in a person.

when you rub, you also apply pressure, that pressure can urge the poop to come out. i think that when your rubbing, you also might be slightly breaking it up and that can further fill the stomach.