Etiological analysis on an outbreak of suspected food poisoning

  Objective  To understand the etiological characteristics of an outbreak of food poisoning suspected to be caused by Bacillus cereus contaminated milk, and provide theoretical basis for food poisoning source identification and clinical treatment.

  Methods  An epidemiological investigation was carried out in 198 cases, and suspected dairy product samples and case samples were collected for pathogen isolation. The isolates of Bacillus cereus were molecularly classified by pulsed field gel electrophoresis (PFGE). The whole genome sequencing (WGS) was carried out and the virulence genes were analyzed. Micro broth dilution method was used for the drug susceptibility test of the isolates.

  Results  The epidemiological investigation indicated that all the 198 cases showed abdominal pain, diarrhea, and fever at different degree, which met the definition of foodborne disease outbreak. A total of 25 strains of B. cereus were isolated, in which 5 were isolated from dairy products, and 20 were isolated from case samples. PFGE analysis showed that there was a high similarity between 13 strains from cases samples and 5 strains from dairy product samples. The drug susceptibility test showed that the 25 B. cereus stains were sensitive to ciprofloxacin, vancomycin, tetracycline, chloramphenicol, gentamicin and imipenem, but completely resistant to ampicillin and penicillin.

  Conclusion  The outbreak of food poisoning was caused by B. cereus contamination. It is necessary to strengthen the health education about food safety to prevent the outbreaks of food borne diseases.