In a new report, the Maricopa County Department of Public Health (MCDPH) says lettuce was the likely cause of an E. coli O157:H7 outbreak at Federico’s Mexican Food restaurant last summer. Ninety-four people were sickened in that outbreak. Two patients developed hemolytic uremic syndrome (HUS), a serious complication of a STEC infection that damages the kidneys and can cause kidney failure, seizures, strokes, and death.
People who ate at the restaurant were sickened between July 18 and July 30, 2013. MCDPH was contacted about a potential cluster of cases with bloody diarrhea on July 30, 2013. Many of the patient’s family members said that the only shared meal was at Federico’s Mexican Restaurant at 13132 W. Camelback Road in Litchfield Park, AZ.
Preliminary results from restaurant samples found high levels of coliform bacteria (an indication of fecal contamination) in the green salsa and lettuce. Identical samples were taken from another Federico’s Mexican Restaurant location as a control. The lettuce had high coliform counts (1400 coliform CRUs/g). No pathogenic E. coli was identified.
Investigations at the restaurant found that lettuce handling protocols could easily have spread contamination from one small batch to others, in the prep sink, while it was being shredded, and storage in a common large container. The highest risk food item was the lettuce, especially when results using only confirmed E. coli cases were considered. When controlling for lettuce, no other food items were a significant risk factor for the illnesses except water.
The report states that lettuce “could have been contaminated in the field from manure or contaminated irrigation water, during processing, transport, handling, or through improper storage. Improper lettuce washing and preparation at the restaurant may have contributed to the spread of disease. The restaurant corrected these processes and complied with all other recommendations and no new cases were identified, effectively ending the outbreak.”
A statement from MCDPH about the outbreak continued, “Cross contamination from another contaminated food source at the restaurant – such as beef, for example – is also a possibility. It is also possible that this restaurant received a small, highly contaminated batch of lettuce that did not go to any other facilities.”
