Arizona officials say tainted lettuce supplied by Midwest Beef and served at a Federico's Mexican Restaurant may be the most likely source that caused 94 people to become ill from E. coli in July.
William Marler, a Seattle attorney who represents victims of foodborne outbreaks, circulated the 32-page, Nov. 25 report by Maricopa County Department of Public Health on his blog.
According to the report, patrons at the Litchfield Park restaurant were likely exposed between July 18 and July 30, and that a case-control study of 180 persons and environmental samples collected on multiple dates appears to implicate contaminated lettuce as the probable source of the outbreak.
The report names Midwest Beef as the supplier of beef and produce to Federico's Mexican Restaurant, and although it supplies produce to other restaurants in the chain, no other confirmed cases of illness due to E. coli were reported from other restaurant locations.
Results of food samples from the restaurant in August revealed high coliform counts in the lettuce, but no pathogenic E. coli. On Aug. 1, elevated levels were found in the green salsa and lettuce. On Aug. 9, elevated levels were found in the lettuce, and on Aug. 16 in the cooler of the implicated Federico's location.
"The specific source of the bacterial exposure is uncertain; however, both the environmental samples and the case-control study implicate lettuce as the most likely contaminated source," the report states. "The 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."
While the contamination may have spread through an ill food handler, no employee illnesses were reported from the restaurant during the month of July and, "this would be a large number of cases to be contracted from a single ill food handler," Arizona officials said.
"Cross contamination from another contaminated food source at the restaurant — such as beef, for example — is also a possibility," according to the statement from the Maricopa County Department of Public Health. "It is also possible that this restaurant received a small, highly contaminated batch of lettuce that did not go to any other facilities."
Health officials provided the restaurant with additional lettuce handling and hand-washing protocols and closed the investigation on Sept. 9.