BACKGROUND: On August 22, 2016, the Missouri Department of Health and Senior Services (MDHSS) was notified about three cases of salmonellosis among patrons of Restaurant A located in a popular tourist area in Missouri, frequented by local and out-of-state visitors. Three cases who dined at Restaurant “A” prior to illness onset sought medical care at a local hospital, and their stool specimens tested positive for Salmonellaby polymerase chain reaction (PCR). Serotype and pulse field gel electrophoresis (PFGE) of the isolates were identical for all three cases. The objective of the investigation by the MDHSS and the LPHA was to identify possible source(s) of exposure and prevent further transmission.
METHODS: Epidemiologic investigation included enhanced surveillance for cases (notifying mandated reporters in Missouri; EpiX notification) and interviewing all case-patients and all restaurant employees. Information from case-patients was collected by phone interview using a standardized questionnaire. An outbreak case was defined as any person who dined at Restaurant A on or after August 1, 2016, developed diarrheal illness within three days of exposure, and was infected with Salmonella serovar Enteriditis matching PFGE Xbal pattern JEGX01.0021. Stool specimens from suspect cases and food samples from Restaurant A were submitted to MDHSS for culture, serotyping, and PFGE analysis. The Missouri Rapid Response Team was consulted to assist with the environmental inspection of Restaurant A and traceback of a suspected food product.
RESULTS: Nineteen persons from three states met the case definition: Missouri (14), Wisconsin (3) and Minnesota (2). The age range of case-patients was 10 to 73 years (median= 43). Fifty-three percent of cases were male. Disease onset dates ranged from 8/14/2016 to 8/25/2016. Two hospitalizations and no deaths were reported. Eleven case–patients were culture-confirmed as Salmonella serovar Enteriditis, and 10 of those had a matching PFGE pattern. Sixteen case-patients recalled eating a dish containing raw or undercooked eggs. Outbreak strain of Salmonellawas isolated from two undercooked eggs food samples. Traceback investigation revealed that Restaurant A purchased eggs from a small local farm which acquired hens from several larger, previously depopulated farms. Infection prevention measures were implemented by public health agency at the restaurant and the egg farm.
CONCLUSIONS: Consumption of foods containing raw or undercooked eggs served at Restaurant A likely caused the salmonellosis outbreak. This investigation highlighted a challenge to preventing foodborne illness among populations who may perceive locally-sourced food as being more wholesome and less likely to cause disease.