Initial adhesion of Listeria monocytogenes to solid surfaces under liquid flow

Area of Science:

• Food microbiology
• Environmental microbiology
• Surface science

Background:

• Listeria monocytogenes persists in food processing environments, posing a food safety risk.
• Strain-specific differences in surface adhesion may explain environmental persistence.
• Understanding adhesion mechanisms is crucial for controlling pathogen contamination.

Purpose of the Study:

• To investigate the initial adhesion rate (IAR) of nine Listeria monocytogenes strains.
• To evaluate adhesion under varying shear stress levels on diverse surfaces.
• To determine the impact of environmental stress on adhesion properties.

Main Methods:

• Utilized a flow chamber setup with microscopy for adhesion measurements.
• Tested adhesion on glass, PVC, and coated glass surfaces (beef extract, casein, milk).
• Assessed surface hydrophobicity via contact angle and bacterial surface properties using Microbial Adhesion To Solvents (MATS).

Main Results:

• Significant strain and surface effects on IAR were observed across all conditions (p<0.05).
• High shear stress generally decreased adhesion; interactions between strain-surface and strain-shear stress were significant (p<0.001).
• Environmental stress (NaCl, low nutrients) altered IAR, but surface hydrophobicity did not correlate with adhesion.

Conclusions:

• Listeria monocytogenes adhesion is complex, influenced by strain, surface type, and fluid shear stress.
• Environmental pre-conditioning significantly modifies bacterial adhesion characteristics.
• No direct correlation found between surface hydrophobicity and adhesion, and persistent strains did not exhibit superior adherence.