Persistence of Bacillus cereus on bakery food-contact surfaces: Biofilm-associated tolerance to disinfectants under organic residue conditions

Post-baking operations in bakery processing environments create opportunities for microbial recontamination through food-contact surfaces that may remain contaminated after routine sanitation. This study investigated the persistence, biofilm forming ability, and disinfectant tolerance of Bacillus cereus isolates recovered from food-contact surfaces in a bakery processing environment. Surfaces were sampled after routine cleaning and sanitation, and bacterial contamination was quantified and identified. Biofilm formation was assessed using crystal violet staining and viable-cell enumeration on stainless steel (SS) and polypropylene (PP) surfaces. The efficacy of chlorine dioxide (ClO 2 ), sodium hypochlorite (NaOCl), quaternary ammonium compounds (QACs), and peracetic acid (PAA) was evaluated against planktonic and biofilm-associated cells under clean and organic-contaminated conditions. Among the investigated foodborne pathogens, B. cereus was the only pathogen detected and was recovered from SS and plastic surfaces at a maximum of 3.11 and 3.84 log CFU/50 cm 2 , respectively. Of 51 B. cereus isolates, four showed biofilm-forming ability. Evaluation of these isolates on SS and PP surfaces revealed variation in biofilm biomass and viable-cell recovery, with low biomass not necessarily corresponding to low viable-cell persistence. These findings indicate that biomass-based assessments may underestimate microbial persistence and contamination risks. EP17-A1 exhibited the highest biofilm-forming ability among the biofilm-forming isolates and was therefore selected for disinfectant evaluation. Biofilm-associated cells were more resistant to disinfectants than planktonic cells. ClO 2 and PAA showed the strongest antimicrobial activity, although ClO 2 generally maintained higher efficacy than PAA under organic-contaminated conditions. Differences in biofilm characteristics, surface material, organic contamination, and contact time contributed to variations in disinfectant performance. Effective control of B. cereus in bakery environments requires integrated sanitation combining thorough pre-cleaning, appropriate disinfectant selection, and sufficient contact time.