Enterotoxin genes, biofilm formation, and antimicrobial and disinfectant resistance of Bacillus cereus isolates from primary producing stages

In this study, we analyzed enterotoxin genes, biofilm formation, and resistance to sixteen antimicrobials and chlorine dioxide (ClO2) in Bacillus cereus group isolates (n = 76) from samples (leaves, seeds, water and nutrients, and soil) from microgreen primary producing farms. Most isolates possessed at least one enterotoxin gene, as well as resistance to β-lactam antimicrobials, and more than half of the isolates showed moderate to strong biofilm-forming ability. Several B. cereus isolates with strong biofilm-forming ability survived ClO2 treatment, thereby preventing their decontamination in samples from microgreen producing farms. When the B. cereus group isolates were treated with ClO2 for 5 min, antimicrobial resistance to rifampin and gentamicin increased. These results provide a useful insight into the development of risk management technologies to ensure the food safety of fresh produce, including microgreens, with a particular focus on the primary production stages.