Unfortunately, it is possible to build up a tolerance to some types of food borne bacteria. It’s hardly worth it, though. In countries where food-borne pathogens are common, kids usually don’t survive to 5. Dysentary still claims many in developing nations. Even when a person acquires some immunity, there’s often permanent effects. .As an example, a relative got a bad case of salmonella from working at KFC. Later on, he got salmonella again, but it only manifested as constant gut problems that lasted for years, but not nearly as severe. A specialist found that he was harboring salmonella, but it was mostly kept in check by the body. Antibiotics and he was cured.