Abstract
This study describes the simultaneous Bacillus cereus growth and cereulide formation, in culture medium and cereal-, dairy-, meat-, and vegetable-based food matrices. First, bacterial growth experiments were carried out under a wide range of temperatures (from 9 to 45°C), using the emetic reference strain F4810/72, in the above-mentioned matrices. Then, the generated data were put in a modeling framework where the response variable was a vector of two components: the concentration of B. cereus and that of its toxin, cereulide. Both were considered time-, temperature- and matrix-dependent. The modeling was carried out in a series of steps: the parameters fitted in one step became the response variable of the following step. Using the square root link function, the maximum specific growth rate of the organism and the time to the appearance of quantifiable cereulide were modeled against temperature by cardinal parameters models (CPM), for each matrix. Finally, a validation study was carried out on an independent data set obtained in the same matrices and using various Bacillus cereus strains. Results showed that both growth and toxin-formation depended on the food matrix and on the environment but not in the same way. Thus, the matrix (culture medium), where the highest growth rate of B. cereus was observed, was not the medium where the shortest time to quantifiable cereulide occurred. While the cereal-based matrix generated the smallest growth rates (0.41-times smaller than culture medium did), quantifiable cereulide appeared in it at earlier times compared to the other tested matrices. In fact, three groups of matrices could be distinguished based on their ability to support cereulide formation (1) the cereal-based matrix (highest), (2) the culture medium and the dairy-based matrix (intermediate), and (3) the meat- and vegetable-based matrices (lowest). This ranking between the matrices is quite different from that based on their suitability to the growth of the organism. Our models can be used in HACCP studies, to improve shelf-life predictions and, generally, microbiological food safety assessments of products for which B. cereus is the main concern.
Highlights
The diarrheal illness is induced by heat labile enterotoxins produced in the small intestine by vegetative cells: the non-hemolytic enterotoxin (NHE), the hemolysin BL (HBL), as well as the cytotoxin K (CytK) (EFSA, 2016; Visiello et al, 2016)
We describe the growth of the reference emetic B. cereus strain F4810/72 and its cereulide formation simultaneously, by vector-based predictive models, with special emphasis on the tertiary modeling of the effect of the matrix on the model parameters
This work provides new models to describe B. cereus growth and time to cereulide formation by emetic strain F4810/72 when artificially inoculated in BHI, cereal, dairy, meat- and vegetablebased products
Summary
Bacillus cereus is a ubiquitous pathogen, commonly found in raw materials and occasionally in processed foods, such as rice, milk and dairy products, meat and meat products, pasteurized liquid eggs, ready-to-eat vegetables, and spices (Altayar and Sutherland, 2006; Wijnands et al, 2006; Hoton et al, 2009; Ceuppens et al, 2011; El-Arabi and Griffiths, 2013; Messelhäusser et al, 2014; Esteban-Cuesta et al, 2018; Fasolato et al, 2018; Park et al, 2018). B. cereus can produce two types of food poisoning illnesses: the diarrheal and the emetic syndromes appearing 8–16 h and 1–5 h after the ingestion of contaminated food, respectively (Messelhäusser and Ehling-Schulz, 2018). The emetic illness is triggered by the cereulide toxin, preformed in the food before ingestion (Ceuppens et al, 2011; Visiello et al, 2016). Cereulide is thermostable as it withstands a heat treatment of 126◦C for 90 min. It is not inactivated by the proteolytic enzymes of the gastrointestinal tract (not cleaved by pepsin or trypsin) and can lead to toxigenesis (Agata et al, 1994, 1995; Rajkovic et al, 2008; Lücking et al, 2015; EFSA, 2016). Even if B. cereus cells were inactivated by appropriate treatments during food processing, cereulide would most likely remain intact and present in the food at consumption
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
