Outbreak Investigation and Microbiological Characterization of a Suspected Food Poisoning Incident in a School Cafeteria in Katsina State

Foodborne illness outbreaks in institutional settings such as school cafeterias demand rapid epidemiological and microbiological investigation to identify causal agents, prevent further cases, and implement corrective actions. This study documented the investigation of a suspected food poisoning outbreak affecting 87 students at a secondary school in Katsina State, North West Nigeria. An outbreak investigation team conducted case interviews using structured questionnaires, identified suspect food items through food history analysis, and collected food remnants, kitchen surface swabs, and stool samples from symptomatic students. Microbiological processing included selective culture for Salmonella, Staphylococcus aureus, Bacillus cereus, and Clostridium perfringens. Attack rates for individual food items were calculated to identify the vehicle of infection. Results implicated rice pudding served at lunch as the primary vehicle (attack rate: 72.4%) compared to 8.9 percent among non-consumers. Bacillus cereus emetic toxin-producing strains were isolated from remnant rice pudding samples and stool cultures of 54.3 percent of symptomatic cases, confirming a B. cereus emetic syndrome outbreak. Inadequate cooling and prolonged warm-holding of cooked rice were the critical failure points. These findings demonstrate the utility of systematic outbreak investigation protocols in institutional food safety and call for mandatory food safety training for school cafeteria staff and routine microbiological surveillance of institutional catering services. Keywords: foodborne outbreak, Bacillus cereus, school cafeteria, food poisoning, Katsina.