In August 2013 Minnesota public health officials investigated an outbreak of E. coli O157 among persons who consumed Mexican-style food from a restaurant located in Rochester. Three laboratory confirmed cases had purchased food from the restaurant catering truck at an event on August 16 or August 17. Three other laboratory confirmed cases ate food at the restaurant on August 16 or August 17. There was one probable case. Two cases were hospitalized. There were no deaths.

A case-control study was conducted. In the univariate analysis, no food item was significantly associated with illness. Consumption of tomatoes (6 of 6 cases vs. 12 of 21 controls; p=0.07) approached significance.

An environmental assessment completed at the establishment identified food handling practices that increased the risk for cross-contamination. Raw beef was observed thawing in pans on wire shelving in the walk-in cooler. Other concerns noted included an uncovered ready-to-eat container of food (chips) next to a raw meat preparation area; inconsistencies of how color-coded cutting boards were used; and a spray bottle of full-strength bleach.

Investigators concluded that the outbreak was associated with the restaurant although the specific vehicle and source of contamination was not identified.