An all-too-common problem for foodborne illness investigations is that the only real evidence gets eaten. That appears to be what happened with the E. coli illnesses in Vermont last month, where 11 people had E. coli O157:H7 infections that state health officials blamed on likely contamination from undercooked hamburgers. Safety News last reported on the outbreak associated with the popular Worthy Burger restaurant and brew pub in South Royalton, VT, on Oct. 20, when it was still widely believed that Shiga toxin-producing bacteria had been found in an unopened package of beef on the shelf of Worthy Burger’s walk-in cooler. That in turn raised the question of why — after a month — there had not been any recall. After that story was published, USDA’s Food Safety and Inspection Service (FSIS) responded to our inquiries, and an update was included in the original story to state that there was no recall because the ground beef sample, which we thought had tested positive for E. coli O157:H7, did not contain the illness-causing H7 antigen, nor did it contain Shiga toxin-producing bacteria. Therefore, the product “is not adulterated and subject to recall,” said Gabrielle Johnston, FSIS public affairs specialist, adding, “FSIS continues to work closely with our public health partners on finding the source of this outbreak.” FSIS spokesman Adam Tarr then underscored the dilemma by telling Food Safety News that “Shiga toxin-producing bacteria were not found at the restaurant — or at all, for that matter.” However, no product to compare to the outbreak strain does not let Worthy Burger off the hook. It means that the final report likely will have the benefit of pulsed-field gel electrophoresis (PFGE) patterns, also known as DNA fingerprints, but will also have to rely on good, old-fashioned epidemiology.

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