Prevalence, Enterotoxin Gene Profiles, Psychrotrophic Characteristics, and Antibiotic Resistance of Bacillus cereus Isolated from Ready-to-Eat Foods

Bacillus cereus is an endospore-forming opportunistic pathogen with global distribution, responsible for two distinct gastrointestinal illness types. The present study aimed to determine the occurrence of B. cereus in ready-to-eat (RTE) foods marketed in Samsun, Turkey, and to characterize confirmed isolates with respect to enterotoxin gene carriage, capacity for psychrotrophic growth, and antibiotic susceptibility profiles. One hundred fifty RTE food samples were examined, including spicy paste ( acılı ezme , n = 29) Russian salad ( rus salatası , n = 44), raw meatballs ( çiğ köfte , n = 42), and stuffed grape leaves ( yaprak sarma , n = 35), procured from retail outlets and food service establishments between December 23, 2024, and February 28, 2025, and analyzed in accordance with TS EN ISO 7932:2004. B. cereus was recovered from 30.6% (46/150) of samples overall, with the greatest contamination frequencies recorded in spicy paste (62.1%, 18/29) and çiğ köfte (57.1%, 24/42). Viable counts in contaminated samples fell within the range of 1.0 × 10 1 to 4.1 × 10³ colony-forming units (CFU)/g. Multiplex polymerase chain reaction screening of the 46 confirmed isolates showed that 28.2% (13/46) carried at least one enterotoxin gene; hbl , nhe , and cytK were each identified in 13.0% of isolates, whereas the emetic toxin gene ces was not detected in any isolate. Ability to proliferate at 7°C was demonstrated in 52.2% (24/46) of isolates. Kirby–Bauer disk diffusion testing revealed that all isolates (100%) were resistant to penicillin, with resistance also recorded for ampicillin (38.5%), tetracycline (30.8%), and clindamycin (23.1%). Collectively, these findings underscore the public health relevance of enterotoxin-carrying, cold-tolerant, and antibiotic-resistant B. cereus in RTE foods and emphasize the necessity of strengthening temperature management and sanitation measures at all stages of the food supply chain.