House of Prime E. coli OutbreakIn July 2014 local, state, and tribal health officials investigated an outbreak of E. coli O157:H7 that occurred primarily among members of the Fond du Lac Band of Lake Superior Chippewa and their guests. Ill persons had attended one or more of several events catered by Jim-N-Jo’s Northland Katering (“Jim-N-Jo’s”) between July 11 and July 16. The events catered by Jim-N-Jo’s included an Elder Picnic (July 11), a wedding (July 12), a three day conference for a private company (July 14-16), and a focus group held on the Fond du Lac Reservation on July 16.
Case patients were identified through routine laboratory surveillance and interviews with persons who attended events catered by Jim-N-Jo’s. A case was defined as an individual who attended an event catered by Jim-N-Jo’s and subsequently developed diarrhea (>3 loose stools in a 24-hour period) that was either bloody or at least 3 days in duration, or an individual who had E. coli O157:H7 isolated from a stool culture with a pulsed field gel electrophoresis (PFGE) pattern indistinguishable from or within 3 bands of the main outbreak pattern by at least 1 enzyme (Xba1 or Bln1). Case patients were interviewed about food consumption at the events and symptoms. Stool samples from ill attendees and food workers were collected and submitted to the Minnesota Department of Health (MDH) Public Health Laboratory (PHL) for bacterial and viral testing.
A total of 199 individuals from seven catered events were interviewed. Of these 74 (37%) reported gastrointestinal illness followed the event, including 57 (29%) who met the case definition. Twenty-one (37%) cases sought medical care at a clinic, 18 (32%) were seen at an emergency department and 9 (16%) were hospitalized. Hospitalizations ranged from 2 to 6 days. No case-patients developed hemolytic uremic syndrome or died. Thirty patients were classified as “probable” cases due to lack of laboratory confirmation of infection with E. coli O157:H7. Twenty seven persons were laboratory confirmed with one of the closely related outbreak strains. These 27 persons attended one or more of three different events catered by Jim-N-Jo’s. Nineteen (70%) isolates were indistinguishable by Xba1 from the subtype designated as EXHX01.0238 by the Centers for Disease Control and Prevention (CDC) (Minnesota pattern designation MN1393), five (19%) isolates were designated as EXHX01.0074 (MN pattern designation WA1ECB281), and one isolate each was designated as EXHX01.0696, EXHX01.0344, and EXHX01.0248.
Jim-N-Jo’s catered at least 12 events from July 5 to July 17. Data analysis of food consumption at the various events resulted in different results. The food item statistically associated with illness at the Elder Picnic was potato salad (37 of 38 cases vs. 44 of 66 controls; odds ratio [OR}, 18.5; 95% confidence interval [CI}, 2.4 to 143.9; p<0.001). None of the food items consumed at the wedding were statistically significant. Only a few attendees of the three-day conference were interviewed. The small number of interviewees prevented data analysis. Participants in the focus group were not interviewed.
Raw celery and onions were the only food items served at all five events with outbreak associated cases. Three events (picnic, 3-day conference, and 3-day meeting) were served the same batch of potato salad that contained raw onions and celery. The celery was also served as part of a vegetable tray at the wedding and as a chopped garnish on the salad bar for the focus group. Chopped onions were also available at all events. In univariate analysis consumption of celery was significantly associated with illness, and onions approached statistical significance. In a multivariate model, only consumption of celery (adjusted OR, 10.1; p=0.004) was significantly associated with illness.
Sanitarians visited Jim-N-Jo’s catering kitchen on July 18. The sanitarian noted inconsistent glove use and issues with date marking. No improper practices or procedures were noted with regard to cooking, cooling, or cross contamination. One employee reported working while ill on July 15 and July 16. A stool specimen submitted by the employee was positive for E. coli O157:H7 with the main outbreak PFGE pattern. The employee reported sampling or tasting food during preparation. Health investigators theorized that this employee was a likely victim of the outbreak and not the source of illnesses in the outbreak.
On July 21 an inspector with the Minnesota Department of Agriculture (MDA) picked up leftover food from Jim-N-Jo’s that was served at the implicated events, including potato salad, strawberries, honeydew, pineapple, and cantaloupe. The potato salad was positive for E. coli O157:H7; all other food samples were negative. Multiple PFGE subtypes were isolated from the potato salad, including the two main patterns isolated from the cases and two other closely related patterns that were not found among the patient isolates. Leftover celery and onions from the same shipment that was served in the potato salad at the wedding and focus group were collected from the caterer and tested. Both products were negative.
Jim-N-Jo’s ordered all fresh produce from Upper Lakes Foods, Inc. The celery that was served at all of the events was received by Jim-N-Jo’s on June 25. MDA staff worked with Pro*Act Distributing and Mann Packing to trace the celery to Martignoni Ranch block 5c in the Salinas Valley, California. California Department of Public Health (CDPH) confirmed the field was owned by Costa Farms and harvested by Mann Packing. CDPH notified the California Food Emergency Response Team (CalFERT) which conducted an inspection of the field and collected water and soil samples on August 13. All samples were negative for E. coli O157:H7. No potential cross contamination issues were observed although it was noted that the field is adjacent to a defunct dairy operation north of Gonzales, California.
Despite the environmental findings in California, public health investigators in Minnesota concluded that this was a foodborne outbreak of E. coli O157 infections associated with multiple events catered by Jim-N-Jo’s Katering. Potato salad served at three events was found to be contaminated with strains of E. coli O157:H7 that was indistinguishable from strains isolated in case-patients. Cases were also identified at two additional events where potato salad was not served. However, celery that was from the same shipment as the celery in the potato salad was served at the two events. A report issued by Minnesota agencies concluded that contaminated celery served in some form at all five events was the most likely vehicle of transmission in this outbreak. The specific route of contamination was not identified, but sampling in the field was limited.