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BACKGROUND: On October 18, 2013, the Allegheny County Health Department identified two Escherichia coli cases through the Pennsylvania National Electronic Disease Surveillance System. Both patients were identified as food handlers at Restaurant A.
METHODS: Case finding was conducted through public messaging, employee surveys, and disease surveillance. All potential case-patients were interviewed using a standard questionnaire. A confirmed case was defined as laboratory- confirmed E. coli O157:H7 with exposure to Restaurant A. A probable case was defined as a patient with compatible symptoms and exposure to Restaurant A but without laboratory confirmation. All employees at Restaurant A were required to submit stool specimens for E. coli testing. A survey was administered to Restaurant A employees to determine symptoms, food history and job duties. SurveyMonkey and Epi Info 7 were used to collect and analyze data. Food Safety Program staff conducted restaurant inspections and collected food samples.
RESULTS: 14 confirmed and 10 probable cases of E. coli were identified. Of the confirmed cases, 9 were Restaurant A employees. Four unique PFGE patterns were identified among confirmed cases. Two E. coli PFGE patterns were identified in ground beef samples from Restaurant A, which matched patterns in human specimens. All confirmed case-patients recalled eating a hamburger from Restaurant A in the 10 days before illness onset; most reported consuming medium to rare hamburgers. 70% of 90 restaurant employees completed the employee survey; 56% recalled eating a hamburger in September or October 2013. Consuming a hamburger was significantly associated with illness among Restaurant A employees. The restaurant ground boxed beef in-house to make hamburgers.
CONCLUSIONS: Multiple matching PFGE patterns identified in human and ground beef specimens and that fact that all confirmed cases consumed hamburgers suggest that the beef was contaminated upon receipt. Restaurant A voluntarily closed, changed beef suppliers and no longer grinds beef in-house. No associated E. coli cases have been identified since the restaurant re-opened. Ground beef that is ground and processed at USDA regulated slaughterhouses is routinely spot tested for pathogens including E. coli; however, boxed beef product is not routinely tested for E. coli and pathogens can be easily introduced through grinding. As in-house grinding by retail establishments becomes more common, spot testing of boxed beef and other preventive actions should be implemented to protect consumers.