Bean Day Outbreak: Salmonella Senftenburg Outbreak Investigation, AL, 2013

BACKGROUND: In October 2013, the Alabama Department of Public Health (ADPH) was notified of a possible fundraiser-associated food borne outbreak.  Reportedly, over 100 individuals were identified ill with gastrointestinal symptoms.

METHODS: A retrospective cohort study was conducted. A hypothesis generating questionnaire (HGQ) was initially used to determine common exposures among ill individuals. The fundraiser flyer listing food items for the fundraiser was obtained from a social media website.  Using information obtained from the HGQ and food items listed on the fundraiser flyer, an outbreak-specific questionnaire (OSQ) was developed. On-site environmental inspections of food preparation facilities used during the fundraiser were conducted and food preparers for the fundraiser were interviewed.  Environmental, food, and clinical (stool) samples were collected and sent for enteric pathogen testing at the ADPH Bureau of Clinical Laboratories. Serotyping and pulsed-field gel electrophoresis (PFGE) identification was performed on all samples.

RESULTS: ADPH staff identified 134 exposed individuals, 73 (54%) individuals were interviewed with the OSQ.  Of those interviewed, 50 (68%) reported illness. The most commonly reported signs and symptoms were diarrhea, extreme tiredness/weakness, and abdominal pain.  There was no statistically significant association detected between food items served at the fundraiser and illness. Environmental inspection and interviews suggested multiple opportunities for food cross contamination. Thirty environmental, 14 food, and 13 stool samples were obtained for enteric pathogen testing. Salmonella senftenberg was isolated in two environmental samples obtained from one food preparation facility, nine food samples (7 from beans served during the fundraiser), and all stool samples. The PFGE patterns for the positive environmental, food, and stool samples matched each other and were a 100% match with isolates that had the JMPX01.0366 outbreak pattern in the national PulseNet database. Ten additional confirmed cases associated with this outbreak were later identified through laboratory reporting and matched the JMPX01.0366 outbreak pattern.

CONCLUSIONS: A Salmonella senftenberg outbreak occurred in association with a fundraiser in Alabama.  The collective descriptive epidemiological data, environmental investigation, and laboratory results supported the hypothesis that the beans served during the fundraiser was the contaminated food source.  How or at what point during the food preparation the beans became contaminated with S. senftenburg could not be definitively determined but opportunities for cross-contamination were identified.