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

Abstract

In this study, we analyzed enterotoxin genes, biofilm formation, and resistance to sixteen antimicrobials and chlorine dioxide (ClO 2 ) 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 ClO 2 treatment, thereby preventing their decontamination in samples from microgreen producing farms. When the B. cereus group isolates were treated with ClO 2 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. • Bacillus cereus group isolates from microgreen primary producing farms were studied. • Most of the isolates possessed at least one enterotoxin gene. • None of the isolates were susceptible to β-lactams and fluoroquinolones. • Some B. cereus showed strong biofilm-forming ability and resistance to ClO 2 . • Resistance to several antimicrobials was increased after exposure to ClO 2 .