In Vitro and In Planta Evaluation of Bacillus Strains Against a Strain of Enteropathogenic Escherichia coli in Mung Bean Sprouts

Edible sprouts, including mung bean sprouts, are nutritionally valuable but have frequently been associated with foodborne outbreaks. Control measures like seed disinfection have not fully prevented outbreaks. This study evaluated the ability of spore-forming Bacillus strains isolated from mung bean sprouts to inhibit E. coli O55:H7 colonization during seed sprouting. Several Bacillus isolates added to the germinating seeds reduced E. coli populations in sprouts by 4.0-5.4 log CFU/g compared to untreated controls. While some strains impacted sprout growth, highly antagonistic isolates, such as MBm1 and MBm6, demonstrated robust activity with no adverse effects. Notably, in vitro antagonistic activity on agar plate did not consistently predict inhibition of E. coli in sprout colonization assays, whereas colony morphology was a better predictor for in planta activity. Bacillus strains formed complex biofilms on agar and sprout surfaces, suggesting biofilm-mediated antagonism. Fluorescence microscopy confirmed reduced E. coli attachment and growth in the presence of antagonistic Bacillus strains. These findings indicate that Bacillus strains may serve as effective biocontrol agents to enhance sprout safety, and that multistrain formulations may be required for broader protection. Further research is needed to validate efficacy against diverse pathogens under commercial conditions.