Characterization of the Bacillus cereus Group Isolated from Ready-to-Eat Foods in Poland by Whole-Genome Sequencing

<i>Bacillus cereus sensu lato</i> can contaminate food and cause food poisoning by producing toxins such as cereulide, toxin BL, and cytotoxin K. In this study, we retrospectively analyzed <i>B. cereus sensu lato</i> from retail food products and food poisoning cases using PCR methods to determine their virulence profiles. A new toxin profile, encoding all four toxins (<i>hbl</i>, <i>nhe</i>, <i>cytK</i>, <i>ces</i>), was found in 0.4% of isolates. The toxin profiles, classified into A-J, revealed that 91.8% harbored <i>nhe</i> genes, while <i>hbl</i>, <i>cytK</i>, and <i>ces</i> were detected in 43.8%, 46.9%, and 4.2% of isolates, respectively. Whole-genome sequencing (WGS) identified four distinct species within the <i>B. cereus</i> group, with 21 isolates closely related to <i>B. cereus sensu stricte</i>, 25 to <i>B. mosaicus</i>, 2 to <i>B. toyonensis</i>, and 1 to <i>B. mycoides</i>. Three novel sequence types (STs 3297, 3298, 3299) were discovered. Antibiotic resistance genes were common, with 100% of isolates carrying beta-lactam resistance genes. Fosfomycin (80%), vancomycin (8%), streptothricin (6%), tetracycline (4%), and macrolide resistance (2%) genes were also detected. These results highlight the genetic diversity and antibiotic resistance potential of <i>B. cereus sensu lato</i> strains in Polish food products.