Outbreak of Salmonella Javiana Involving Multiple Infected Food Handlers— Tennessee

BACKGROUND:  Outbreaks of Salmonella serotype Javiana have been associated with multiple food vehicles, particularly with tomatoes.  In August 2014, a local hospital notified the Tennessee Department of Health (TDH) of a recent increase in Salmonella cases. An outbreak investigation was initiated to confirm the etiology, mode of transmission, and halt the continuation of the outbreak.

METHODS:  Concurrent epidemiological, laboratory, and environmental investigations were conducted. Analyses of routine case interviews and a case-control study were performed. Credit card receipts were collected from the restaurant to identify probable cases and enroll controls. Logistic regression was used to assess exposures among cases and controls in SAS 9.3. Stool specimens were collected, and isolates were subjected to molecular characterization by serotyping and pulsed-field gel electrophoresis (PFGE). An environmental assessment was conducted, and employees were interviewed about recent gastrointestinal illness.

RESULTS:  Outbreak isolates were characterized as Salmonella Javiana with PFGE pattern JGGX01.0217. During August 1-September 5, 32 of 38 (84%) case-patients infected with the outbreak strain reported eating at one common restaurant, Restaurant A, within the seven days before becoming ill.  Dates of illness onset ranged from August 7- September 2.  Confirmed cases were defined as individuals that ate at Restaurant A after August 1 with a history of diarrhea and stool culture of Salmonella Javiana. Thirty-nine confirmed and probable cases and thirty-two controls were enrolled in the analytical study. Analyses were conducted on 37 food items, including tomato-containing menu items. Consuming cheese dip had the highest odds of developing diarrheal illness (OR: 2.13, 95% CI: 0.78-5.86), but the association was not statistically significant. The environmental assessment revealed 12 food handlers ill with diarrhea from August 6-September 2. Eight of the employees tested positive for the outbreak strain. Five of the food handlers with Salmonella reported working while ill with diarrhea. Food handlers were advised not to return to work while symptomatic, and to remain excluded until they produced a negative stool culture.

CONCLUSIONS:  This was a large salmonellosis outbreak involving multiple infected food handlers. No single food item was associated with illness. It is likely that transmission occurred by cross-contamination of multiple foods due to the large number of ill food handlers. Standardized exclusion policies for ill food handlers should be implemented and followed in restaurants. This outbreak prompted review of state exclusion guidelines for high-risk occupations diagnosed with enteric pathogens using culture or culture-independent methods.