Salmonellosis outbreak in a restaurant associated with French toast sandwich—Chiayi County, Taiwan, 2018

  • Water or foodborne
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Background:
Salmonella is a common pathogen in foodborne outbreaks in Taiwan; however, the contamination routes remain largely unknown. On April 27, 2018, Taiwan CDC was notified of a salmonellosis outbreak related to a restaurant, with 13 patients laboratory-confirmed. We investigated the outbreak to identify infection source and recommend preventive measures.

Methods:
We conducted a case-control study. We recruited and interviewed patients with gastroenteritis and patrons through reviewing medical records from an emergency department, foodborne illness complaints, restaurant orders, and referrals from patrons. We defined case-patients as patrons with diarrhea occurring within 72 hours after consuming the restaurant foods during April 16–27, 2018. We conducted bivariate analyses to identify foods associated with illness. Stools from patients and food handlers, foods and environmental samples were tested for enteric pathogens. Salmonella isolates were analyzed using pulse-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). We inspected the restaurant and reviewed surveillance camera recordings to identify possible source of contamination during food preparation.

Results:
We identified 47 cases; 14 were hospitalized and one died. Median incubation period was 10.5 hours (range: 0.5–52.5 hours). Main symptoms included diarrhea (n=47, 100%), fever (n=32, 68%) and abdominal pain (n=31, 66%). Compared with 44 controls, case-patients were more likely to have eaten French toast sandwich (OR: 102.4, 95% CI: 18.7–952.3). Salmonella Enteritidis were yielded from 16 case-patients, sharing indistinguishable PFGE and WGS results. Foods and food handler samples tested negative. Environmental inspection did not find lapses in food safety practices. Surveillance camera recordings showed that handmade liquid eggs, one ingredient of French toast sandwich, was contaminated by egg shells, stored under room temperature and reused for days.

Conclusion:
French toast sandwich containing handmade liquid eggs could be the infection source. Restaurants should use pasteurized liquid eggs and ensure safe processing and storage techniques.

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