Role of Bacillus cereus biofilm formation behavior in virulence and pathogenic characteristics

This study aimed to examine the potential link between Bacillus cereus biofilm formation, virulence, and pathogenicity. The biofilm formation abilities of nine B. cereus strains isolated from food and two reference strains (ATCC 10876 and ATCC 25621) were measured using a crystal violet assay. Among the tested strains, three strains (GIHE 617-5, GIHE 86-09, and GIHE 728-17) and both reference strains were capable of biofilm formation. A positive correlation was obtained for higher cell surface hydrophobicity and increased biofilm formation. In contrast, HPLC analysis for elevated autoinducer-2 (Al-2) production revealed a negative impact on biofilm formation. PCR data indicated that all tested strains were capable of producing common B. cereus enterotoxins, including Hbl—A, C, and D, CytK, Nhe—B and C, EntFM, and BceT, but were negative for production of the emetic toxin cereulide and the pore-forming toxin Hly II. Meanwhile, RT-PCR data revealed a close correlation between high biofilm formation and the upregulation of several tested virulence genes for selected strains. However, elevated upregulation of virulence genes was not consistent in all of the higher biofilm-forming strains. Cytotoxicity analysis revealed higher virulence characteristics compared to those of low biofilm-forming strains.