On May 28, 2021, several gastroenteritis cases were reported among students and staff of a high school on a Greek island. Lunches were delivered daily at the school by a catering company. We conducted a retrospective cohort study. Cases were defined as students or school staff presenting with diarrhea and abdominal pain between May 27 and 29, 2021. We used a self-administered questionnaire to collect the data. In the univariate analysis, we calculated food-specific attack rates (ARs), relative risks (RRs), and confidence intervals (95% CIs). Statistically significant variables (p < 0.05) were included in the multivariable model. Stool samples were collected from students on the same day of notification and were tested for bacteria, viruses, and parasites. The local food safety authority also inspected the school and the catering company premises. The food samples were sent to the reference laboratory for analysis. We received 129 responses from 174 students and staff members (response rate: 74%). Thirty cases were identified (AR, 23%). Of the 11 significant food items in the univariate analysis, the consumption of spaghetti with minced meat on May 27 (odds ratio 53.40, 95% CI: 3.9-736.1, 97% of cases exposed) was independently associated with the onset of gastroenteritis. Clostridium perfringens was detected in two of the three students' stool samples. Six samples from spaghetti with minced meat were positive for C. perfringens and four of those also tested positive for Bacillus cereus. Environmental investigation revealed non-compliances concerning food personnel training and Hazard Analysis and Critical Control Points (HACCP) plan implementation in the food establishment. Timely investigation and samples collection allowed the identification of the probable source of the outbreak. Changes, regarding the reception and distribution of meals in the school, were applied. Recommendations were given to the catering establishment focusing on adequate personnel training and HACCP issues, especially regarding temperature/time controls during all production, handling, and distribution phases.
Keywords: Clostridium perfringens; gastroenteritis; outbreak; school; toxin.