A Food-borne Outbreak of Gastroenteritis caused by different Salmonella serotypes in two universities，Xiamen, Fujian, China, 2012

Abstract

We investigated a diarrhea outbreak in two universities to identify the etiological agent of the outbreak, the source of infection, the mode of transmission and the risk factors. A case-control study was conducted between the case-students and the asymptomatic control-students who were selected randomly and were frequency matched by class and age, and the source of food or water investigated. 0.25% of total 22,404 students (excluding teachers) developed Salmonella. 96% (54/56) of case-students and 30% (35/117) of control-students consumed bread products provided by the same vendor (odds ratio (OR)=63.3, 95% confidence interval(CI): 14.9-550.7).Among students who consumed the bread, 96% (52/54) of case-students and 9% (3/35) of control-students ate egg-sandwiches (OR=277.3, 95%CI: 43.9-1,750.8). 7 strains of Salmonella Enteritidis and 6 strains of Salmonella Chester were isolated from the case-students or the food samples. Pulsed-field gel electrophoresis typing (PFGE) showed the same patterns respectively. The outbreak of gastroenteritis was mainly caused by egg-sandwiches contaminated with different serotypes of Salmonella.