BIOFILM FORMATION OF Bacillus cereus ON FOOD-CONTACT SURFACE: IMPLICATION FOR INFANT FORMULAS SAFETY

Bacillus cereus is a sporeforming bacteria associated with foodborne illnesses. This study assessed the effect of the matrix on B. cereus biofilm formation on stainless steel, glass, and polypropylene by comparing Tryptic Soy Broth (TSB) and infant formula as matrices. Three strains (C5DI17, C5DB22, and C1BPN) from the Industrial Microbiology Laboratory of UFMG culture collection, isolated from cassava products, were selected based on their distinct antimicrobial resistance. For biofilm assays, the coupons were sanitized and sterilized at 121 °C for 15 minutes, the cell concentration was adjusted to 0.5 McFarland, and each medium and surface was inoculated separately. The incubation was carried out at 30 °C for 24 hours, followed by washing with PBS to remove planktonic cells and vortexing the cells. Sessile cells were recovered and quantified using the microdroplet method. For the C5DI17 strain, in infant formula, polypropylene showed the highest adhesion (8 log CFU/cm²), followed by glass and stainless steel (7 and 6 log CFU/cm², respectively). In TSB, polypropylene showed 6 log CFU/cm², glass 5 log CFU/cm², and stainless steel 3 log CFU/cm². For the C5DB22 strain, polypropylene and glass showed similar counts, with 7 log CFU/cm² in infant formula and 6 log CFU/cm² in TSB, whereas stainless steel showed 6 log CFU/cm² in infant formula and 4 log CFU/cm² in TSB. For the C1BPN strain, glass showed the highest adhesion in infant formula (8 log CFU/cm²), followed by polypropylene (7 log CFU/cm²) and stainless steel (6 log CFU/cm²), while in TSB, all surfaces showed 7 log CFU/cm². Biofilms were observed on all surfaces. In 88.9% (16/18) of the assays, cell density was higher in infant formula than in TSB. The results may be linked to the presence of lactose and oligosaccharides in infant formula, which provide readily metabolizable carbon sources that promote microbial growth and extracellular matrix production. Polypropylene surfaces showed the highest microbial adhesion, followed by glass and stainless steel, raising concerns about their use in baby bottle composition. The findings reinforce the need for more effective control strategies.