In June 2011, state and local health officials investigated an outbreak of Staphylococcus aureus intoxications at a graduation party in Olmstead County, Minnesota. Thirteen outbreak associated cases were identified. No one was hospitalized and no one died.

Food items served at the event included pulled pork and pulled beef provided by a restaurant in Rochester; pickles, watermelon, cake and condiments purchased at a grocery store; and, homemade potato salad. Results of a case control study showed consuming potato salad was the only food item significantly associated with illness. The potato salad was prepared at the house of the party host. Temperature abuse of the potato salad during preparation likely led to conditions conducive to S. aureus replication and formation of enterotoxin A. The source of the S. aureus contamination was not identified, but most plausibly occurred during handling/peeling of the hard-boiled eggs and other salad ingredients by a food preparer colonized with S. aureus.

Leftover potato salad and hard boiled eggs were collected from the party host. Both food samples were cultured, and S. aureus colonies were isolated from both foods.