An outbreak of gastrointestinal illnesses occurred at restaurant in Bloomington, Minnesota in April 2011. Three outbreak associated cases were identified. The median incubation period for the cases was 1 hour (range, 0.5 to 3.5 hours). The duration of illness for the two cases who had recovered by the time they were interviewed was 7.5 and 11 hours. No one was hospitalized and no one died.

City of Bloomington Environmental Health Division (CBEHD) sanitarians conducted an onsite investigation. Cooked rice was observed being held in an improperly functioning cold well for up to 2 hours prior to being fried.

Leftover fried rice collected from complainant’s homes was negative for Staphylococcus aureus. One colony of Bacillus cereus was isolated from fried rice. However, that colony tested negative for the emetic toxin gene by PCR.

Investigators concluded that while the etiology was not confirmed, the symptoms, incubation periods, and likely vehicle of fried rice were characteristic of the emetic form of Bacillus cereus.

Malfunctioning cold hold equipment likely led to the amplification of bacteria and toxin production in the rice.