Laboratory diagnosis and analysis of a food poisoning outbreak caused by Salmonella

Objective To understand the epidemiological and etiological characteristics of a food poisoning outbreak occurred in Chifeng, Inner Mongolia autonomous region, in May 2014 and identify the risk factors and possible infection source. Methods Active case finding was conducted according to the case definition, and patients' anal swabs and stool samples, food samples and environment samples were collected for pathogen isolation which was determined by biochemical test and serological test. Pulsed-field gel electrophoresis (PFGE) was performed for the subtyping of the isolates. The drug susceptibility of the isolates was detected with micro-broth dilution method. Results A total of 43 cases were found, all of them had attended a dinner party. Salmonella Enteritidis was detected in 7 anal samples, no Shigella, Staphylococcus aureus, diarrheagenic Escherichia coli and Bacillus cereus were detected. The 7S. Enteritidis strains shared same PFGE pattern after the digestion with XbaⅠ, indicating that the strains were from same clone. Comparison with the data from PulseNet China Database revealed that the PFGE pattern of the strains detected in this outbreak was highly homologous with the common PFGE pattern of S. Enteritidis strains isolated in China. Conclusion The food poisoning outbreak was caused by S. Enteritidis and the S. Enteritidis strains shared the same PFGE pattern with the predominant pattern of S. Enteritidis isolates in China.