Salmonella Outbreak Among Patrons of an Upscale Restaurant — Washington, DC, 2015

BACKGROUND: Salmonella causes approximately 1.2 million infections and 450 deaths annually in the United States. On September 8, 2015, a local emergency department reported 4 possible cases of Salmonella to the District of Columbia Department of Health (DC DOH). All patients had eaten at Restaurant A. We sought to identify cases and the source of contamination to prevent additional illness.

METHODS: A case-control study was conducted to identify specific food items associated with illness. A case was defined as gastrointestinal illness within 7 days after eating at Restaurant A during July–September 2015. Control subjects had eaten at Restaurant A and reported no subsequent illness. Chi-square tests were performed to examine food items associated with illness. DC DOH’s initial inspection of the restaurant was conducted on September 9. The DC Public Health Laboratory performed pulsed-field gel electrophoresis (PFGE) analysis on clinical specimens, and tested food and environmental samples collected during September 9–11. 

RESULTS: Among 219 patrons interviewed, 150 (68%) were cases. Among cases, 11 (7%) were hospitalized and 38 (25%) were confirmed to have Salmonella serovar Enteritidis. Meal dates for cases occurred during July 31–September 9, 2015. Approximately 68% of cases were female and 74% were non-Hispanic white. The mean age of cases was 37 years (range: 9–72 years). Cases were more likely than controls to have eaten truffle mushroom croquettes (58% versus 30%; p <0.001) and truffle risotto (21% versus 9%; p = 0.02); both dishes contained truffle oil. Cases were more likely than controls to have eaten a food item that contained truffle oil (86% versus 49%; p<0.001). During the restaurant inspection, multiple food safety risk factor violations were noted. The restaurant’s license was temporarily suspended on September 10 due to the apparent Salmonella outbreak. The PFGE patterns for the first two hospitalized cases were indistinguishable (XbaI PFGE pattern JEGX01.0008). None of the food or environmental samples grew Salmonella, including the truffle oil samples.

CONCLUSIONS:  Despite the absence of laboratory confirmation of Salmonella in food and environmental samples, epidemiologic evidence indicates foods containing truffle oil were possible sources of illness. The restaurant was required to address food safety risk factor violations and remove food items containing truffle oil from the menu before its license was restored. No new cases have been reported since the restaurant reopened.