Prevalence of the Strains of Bacillus cereus Group in Artisanal Mexican Cheese

Bacillus cereus is a microorganism associated with food poisoning. It has been found in products, such as milk and dairy products. The aim of this study was to isolate and identify B. cereus group strains in artisan cheeses sold in southwestern Mexico, as well as its toxigenic profile, its psychrophilic ability, and its biofilm production. B. cereus isolation was performed on Mannitol Yolk Polymyxin (MYP) agar and this was molecularly confirmed by the amplification of the gyrB gene. Polymerase chain reaction was used to determine the toxigenic profile, amplifying conserved regions of hblABD and nheABC operons, which code for the subunits of Hbl and Nhe toxins, respectively, as well as ges and cytK genes, which code for toxin cereulide and cytotoxin K (Cytk). Frequency of B. cereus contamination in artisan cheeses was 29.48% (23/78), and the bacterium was isolated in similar quantities in all types of products. All strains were amylase positive, and 60.86% (14/23) were able to produce biofilm; 91.30% (21/23) of the strains were psychrophilic. In most of the strains, at least one gene related to enterotoxins was identified (21/23). B. cereus strains in this study have a high toxigenic potential, which increases the risk of food poisoning due to the consumption of artisan cheeses made in Mexico.