The toxin is produced in the intestine and it is the toxin that really cause the illness.
An example of an organism that causes foodborne illness in this manner is Clostridium perfringes.
Large numbers of the bacteria, usually in the millions, need to be ingested to cause illness.
These bacteria produce a spore, which is a dormant form of the organism. Vegetative cells may form a spore when the conditions for survival are not optimal for the cell, such as high heat or lack of water and food.
Heat does not destroy spores. Once the conditions are conducive to growth again, the spore will again become a vegetative cell. A typical case of food borne illness occurs when a piece of meat is cooked, but the spore survive.
Then, if the meat is not cooled properly the spores revert back to their non-dormant vegetative form and reproduce to high numbers.
When the food contaminated with Clostridium perfringes is eaten, the organism grows in the small intestine and produces a toxin that causes illness.
Toxico-infection of Bacteria