Abstract

OBJECTIVES
In August 2024, a large outbreak of gastrointestinal illness was reported among workers at a workplace in Daejeon, Republic of Korea, where bulk meals were served. This study investigated the epidemiological and microbiological characteristics of the outbreak to identify the causative pathogen, the infection source, and possible contamination routes.
METHODS
A comprehensive epidemiological investigation was conducted, including case identification, retrospective cohort analysis, laboratory confirmation, and pulsed-field gel electrophoresis (PFGE). Attack rates, relative risks (RRs), and 95% confidence intervals (CIs) were calculated. Environmental and distribution chain assessments were also performed to trace the sources and transmission pathways.
RESULTS
A total of 75 individuals developed gastrointestinal symptoms, of whom 27 had laboratory-confirmed enterotoxigenic Escherichia coli (ETEC) O159 infection. The mean and median incubation periods were 70.5 and 72.0 hours, respectively. The attack rate was significantly higher among kimchi consumers than among non-consumers (RR, 1.47; 95% CI, 1.08 to 2.00). PFGE identified ETCX01.332 as the predominant pattern among patient and kimchi isolates. Distribution tracing indicated that the implicated kimchi was produced at a factory in Gyeonggi Province and supplied to multiple catering facilities, leading to additional outbreaks in Seoul and Gyeonggi Province. However, the exact contamination point(s) during production or distribution remained undetermined.
CONCLUSIONS
This outbreak was attributed to ETEC O159, with kimchi suspected as the infection source. These findings provide rare evidence implicating non-heated fermented foods in ETEC transmission and highlight the need for strengthened hygiene standards and real-time monitoring throughout the production, distribution, and handling of fermented foods.

• Keywords: Enterotoxigenic Escherichia Coli; ETEC; Foodborne Infections; Outbreaks