In December 2009 the Minnesota Department of Health (MDH) uploaded results of molecular testing by Pulsed Field Gel Electrophoresis (PFGE) of an E. coli O157:H7 isolate cultured from a patient stool specimen to PulseNet, a national database of molecular subtyping or “fingerprinting” of foodborne disease causing bacteria. The Minnesota isolate was assigned PulseNet 2-enzyme pattern designation EXHX01.0248/EXHA26.0569. PulseNet staff quickly identified 13 additional isolates in patients residing in 11 states.
The Centers for Disease Control and Prevention (CDC) and state investigators identified 25 patients residing in 17 states (California, Colorado, Florida, Hawaii, Iowa, Indiana, Kentucky, Michigan, Minnesota, Nebraska, Nevada, Ohio, Oklahoma, South Dakota, Tennessee, Utah, and Washington) as being part of the outbreak. Illness onsets ranged from October 3, 2009 to January 31, 2010. Twelve patients were hospitalized, 1 developed Hemolytic Uremic Syndrome, and 1 patient died. Of the 22 cases interviewed, 14 (64%) reported eating steak at a family-style restaurant; 9 of the 14 ate steak at an Applebee’s. Among the 8 patients who did not report eating steak, 7 ate ground beef.
Considered together these factors showed that patients counted as outbreak-associated cases were sickened as a result of exposure to a common source. Using the incubation period for an E. coli O157:H7 infection (1 to 10 days, with 3 to 5 days being most common) to assess risk factors for infection, public health investigators determined that several patients consumed mechanically tenderized steaks produced by National Steak and Poultry (NSP).
Trace back investigation of the steaks eaten at Applebee’s showed that the steaks were mechanically-tenderized and came from a single processor, National Steak and Poultry (NSP) in Oklahoma. On December 24, 2009 the company recalled 284,000 pounds of beef products due to contamination with E. coli O157:H7. On January 6, 2010 the CDC published a final investigation update, which was supplemented by an MDH report published later in 2010.
However, investigators also learned that not all outbreak-associated patients consumed steak in the week before illness onset. These patients, including Robert Danell, consumed ground beef. More than 40% of the patients infected with strain EXHX01.0248/EXHA26.0569 who were interviewed reported consumption of ground beef and not steak. The MDA conducted a trace back of ground beef consumed by Minnesota patients. MDA investigators learned that these patients consumed ground beef that was purchased at two different retailers – Cash Wise and Coborns and one distributor – Upper Lakes Foods. All three purchased ground beef that came directly from J&B Wholesale.
The ground beef sold by J&B Wholesale was traced to Tyson Fresh Meats (Tyson) plants in Illinois, Kansas, and Texas. All three Tyson plants produced ground beef with added lean finely texturized beef (LFTB) product supplied by Beef Products Incorporation (BPI). MDH reported that USDA FSIS noted that JBS Swift (JBS) supplied beef to both BPI and to NSP, although no overlap of product delivery could be unequivocally documented.
On December 30 Robert ate meatballs at lunch served at a Catholic Charities day care program. Catholic Charities purchased the ground beef used in the meatballs from Upper Lakes Foods, Inc. in Cloquet, Minnesota. J&B Wholesale supplied upper Lakes Foods, and as noted, J&B Wholesale got this ground beef from Tyson. Tyson Est. 278 received LFTB from BPI, which received trim from JBS.
Robert consumed ground beef on two other occasions prior to his January 4 onset. On December 28 he consumed hamburgers at Catholic Charities. The patties came from Rochester Meats via Upper Lakes Foods. Since no other cases were linked to Rochester Meats the company was not investigated further.
On December 31 Robert consumed ground beef lasagna at his group home. The beef was purchased from Cub Foods with three possible purchase dates in December. Cub Foods ground the beef in-house from trim. Grinding logs showed that Tyson trim, and trim from other unnamed manufacturers, were used in December in ground beef sold at the store. It is unlikely either BPI or JBS provided trim to Cub Foods.
It is therefore well established that Robert was infected with E. coli O157:H7. An isolate (Minnesota Department of Health Specimen ID # 2010001507) cultured from his stool specimen was a genetic match by Pulse Field Gel Electrophoresis (PFGE) and Multiple Loci VNTR Analysis (MLVA) to other patients diagnosed with E. coli O157:H7. Robert and other patients infected with the strain identified by PulseNet to be “EXHX01.0248/EXHA26.0569” were designated by public health investigators to be part of “Outbreak 0912MLEXH-1.” This designation was made based on two enzyme PFGE testing and MLVA testing and temporal clustering of illness onsets.
 See FSIS Recall 067-2009 http://www.fsis.usda.gov/News_&_Events/Recall_067_2009_Release/index.asp