A study on toxin genes and cytotoxicity levels of Bacillus cereus in various ready-to-eat foods and pastry products in Turkey

Abstract

Bacillus cereus is a spore-forming and toxin-producing gram-positive bacteria widely isolated from soils, meat, milk, and vegetables. It is recognized as one of the pathogenic bacteria that can lead to food poisoning and food spoilage in food service systems due to its ease of contamination of foods and lack of guarantee of elimination by pasteurization and sanitation practices. B. cereus causes two types of diseases mainly characterized by diarrhea and vomiting type syndrome with the toxins it produces. Toxins produced by B. cereus are mainly heat-stable emetic toxin and three different heat-labile enterotoxins. Foodborne illnesses of the diarrheal type are caused by the single protein toxin; cytotoxin K (CytK), and both tripartite toxins; hemolysin BL (Hbl), and the non-hemolytic enterotoxin (Nhe), whereas the emetic type, is caused by an emetic toxin cereulide. In this study, 225 ready-to-eat foods and pastry products were analyzed for B. cereus, its toxin profiles, and cytotoxicity effects. Multiplex PCR is used to identify the presence of the Hbl, CytK, and emetic toxin encoding genes. Component-specific antibody-based ELISA tests were utilized to determine the Hbl-L2 and NheB components. Cytotoxic activity of the B. cereus isolates on Vero cells was also identified. In total, B. cereus was detected in 37 out of 225 (16.4%) food samples. From the positive 37 B. cereus isolates, the ces gene was not identified, whereas 91.9% (34) Nhe, 56.8% (21) Hbl, and 8.1% (3) CytK encoding genes revealed positive results on PCR analysis. PCR results were also compatible with ELISA and Cytotoxicity tests. In a nutshell, 16.4% prevalence of B. cereus in foods is insufficient, and the presence or absence of toxin genes may not yield reliable results. It is critical to detect pathogenic B. cereus toxin gene profiles as well as toxin production ability at the same time. This study presents for the first time, data from a cell culture cytotoxicity test using specific monoclonal antibody-based sandwich ELISA and multiplex PCR for ready-to-eat foods and pastry products in Turkey