Antibacterial, anti-biofilm activity and underlying mechanism of garlic essential oil in water nanoemulsion against Listeria monocytogenes

Garlic essential oil (GEO) in water nanoemulsion (GEON) has been reported to possess good stability and broad-spectrum antibacterial activity, but its effect on Listeria monocytogenes is rarely studied. In the present study, the antibacterial, anti-biofilm formation activity and underlying mechanism of GEON against L. monocytogenes were investigated. Results showed that GEON (mean particle size = 136.43 nm) significantly inhibited the growth of planktonic L. monocytogenes, and the minimum inhibitory concentration (MIC) of GEO in the nanoemulsion was 512 μg/mL. GEON could effectively kill L. monocytogenes in a time- and concentration-dependent manner. After GEON treatment, the cell membrane was severely damaged, which was proven by remarkable membrane depolarization and considerable loss of intracellular substances (nucleic acid, protein, and ATP). Moreover, decreased membrane integrity and collapsed cell morphology further confirmed the cell membrane damage. Additionally, GEON significantly attenuated the biofilm formation, enhanced the surface hydrophobicity, and reduced the swimming motility of L. monocytogenes. These results indicate that GEON has the potential to inhibit the planktonic growth and biofilm formation of L. monocytogenes.