Salmonella is the common name given to a type of food poisoning caused by the bacteria Salmonella enteritidis (other types of illnesses are caused by other species of Salmonella bacteria, including typhoid fever. When people eat food contaminated by S. enteritidis, they suffer gastroenteritis (inflammation of the stomach and intestines, with diarrhea and vomiting).

Salmonella food poisoning is most often caused by improperly handled or cooked poultry or eggs. Because chickens carrying the bacteria do not appear ill, infected chickens can lay eggs or be used as meat.

Early in the study of Salmonella food poisoning, it was thought that Salmonella bacteria were only found in eggs which had cracks in them, and that the infecting bacteria existed on the outside of the eggshell. Stringent guidelines were put into place to ensure that cracked eggs do not make it to the marketplace, and to make sure that the...