A Quick Return on Investments in Food Safety

There is no such thing as a good food-borne disease outbreak. But the E. coli O157:H7 outbreak centered in Pennsylvania in early 2011 was at least instructive, showing just how well the U.S. food-safety system can work when all of the players involved work together.

The outbreak – linked to Lebanon bologna, a cold-smoked, fermented sausage – first came to light on 5 March 2011. Just over two weeks later, the U.S. Department of Agriculture (USDA) announced a voluntary recall of 23,000 pounds of potentially contaminated product. In between, a host of laboratory, epidemiology, and regulatory responders worked hand-in-glove to unravel what began as a mystery.

David Sweat, foodborne-disease epidemiologist with the North Carolina Division of Public Health, involved in the multi-state investigation, commented that the American people “wonder about the federal response to food safety issues – whether we’re spending tax dollars wisely. Well, those investments do pay off,” he continued. “I think that’s the real story here; we can see the return on those investments.”

The story actually begins in the Pennsylvania Department of Health’s Bureau of Laboratories, where Carol Sandt (supervisor of the Molecular Microbiology Section of the bureau’s Division of Clinical Microbiology) oversees work related to molecular biology. “I routinely monitor our databases for clusters [of cases involving the same pathogen]. This one happened to involve a type of E. coli O157:H7 that we had seen before in Pennsylvania,” she noted.

A Timely Alert and a Genetic Fingerprint In fact, the laboratory had confirmed eight cases of infection with the bug between 2007 and 2010, but almost all of those cases were widely separated in time. However, Sandt now had seen five cases in two sequential months. “Given that history,” she said, “I alerted our epidemiologists.” On April 7, Sandt posted the bacterium’s PFGE (pulsed-field gel electrophoresis) pattern – a genetic “fingerprint” of the pathogen – onto the national PulseNet database, which stores all PFGE patterns of all the bacteria associated with laboratory-confirmed food-borne illnesses in the United States. The PulseNet network is coordinated by the Atlanta-based U.S. Centers for Disease Control and Prevention (CDC) in collaboration with the Association of Public Health Laboratories (APHL).

CDC officials requested samples of the E. Coli O157:H7 isolates and performed a second type of DNA (deoxyribonucleic acid) fingerprinting: MLVA (Multiple-Locus Variable Number Tandem Repeat Analysis) – which, like the PFGE testing, showed that all five of the patients being treated had been infected with anentical strain of E. coli O157:H7.

In the meantime, Dr. Andre Weltman, an epidemiologist with the Pennsylvania Department of Health, was taking Sandt’s “heads-up” very seriously. “We decided to do hypothesis-generating interviews” with the cluster patients, he said, to determine what food items might be implicated in the outbreak. Lebanon bologna was an early suspect.

Weltman also learned, via PulseNet, that certain nearby states, including North Carolina, had apparently seen some similar cases. “What is critical for these investigations,” he said, “are the outliers. North Carolina was an outlier [with just one case]. To me, sometimes the exception proves the rule.”

Protocols and Procedures: The Keys to a Rapid Response On March 9, Weltman contacted Sweat at the North Carolina public health agency. As it happens, North Carolina is funded through APHL as one of seven CDC OutbreakNet “Sentinel Sites” – all of which share a standard patient interview protocol and other strategies to investigate enteric disease outbreaks. North Carolina also is one of nine states that has fielded a food-protection Rapid Response Team (RRT – funded through the FDA). 

Sweat said that all state epidemiologists and RRT members are “drilled and trained and have standard operating procedures worked out in advance, so when we get a trigger it’s pretty easy to get a well-coordinated response.”

An interview with the one North Carolina outbreak suspect revealed that that patient is originally from Pennsylvania and regularly purchases Lebanon bologna from a warehouse buying club. Although the presumably tainted product had already been eaten, North Carolina officials collected electronic shopper card data from the patient; that data helped USDA officials: (a) to determine the specific brand of Lebanon bologna that had been sold; and (b) working with shipment dates provided by the manufacturer, to hone in on a few specific lots. The Pennsylvania manufacturer agreed to a voluntary recall.

Without such a rapid response, Sweat said, “certainly more people could have consumed this and suffered kidney damage or death. Any number of things could have gone wrong.” Instead, confirmed cases were limited to 14 in a five-state area (Pennsylvania, Ohio, New Jersey, Maryland, and North Carolina). Case closed: Textbook collaboration among all of the responders involved had cracked the investigation in record time.


For additional information on the E. coli outbreak described above and/or the various agencies involved, http://www.cdc.gov/ecoli/2011/O157_0311/

Shari Shea

Shari Shea is director of Food Safety Programs at the Association of Public Health Laboratories (APHL), and prior to assuming that position was the association's PulseNet program manager. She previously served as an Emerging Infectious Diseases training fellow at the Massachusetts State Laboratory Institute.



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