Influence of flow direction and flow rate on the initial adhesion of seven Listeria monocytogenes strains to fine polished stainless steel

Abstract

The effects of flow direction and shear stress on the adhesion of different strains of Listeria monocytogenes to fine polished stainless steel under liquid flow conditions were investigated. Furthermore, the relationship between cell surface properties and cell size and the initial adhesion rate (IAR) was studied. A method, including fluorescence microscopy and a flow perfusion system, was developed and used to examine the real-time initial cell adhesion of different L. monocytogenes species in situ to opaque surfaces under flow conditions.The results demonstrated that shear stress was the determining factor for the initial adhesion of L. monocytogenes under flow conditions. The flow direction in relation to the orientation of surface features (the scratches) could be disregarded. IARs were dependent on the shear stress and strain type. The strain EGDe, which had the lowest IAR, had the largest cell size, was the least hydrophobic and possessed the most electron-donating cell surface. Except for the L. monocytogenes strain EGDe, no clear correlations were found between the IAR and cell surface properties, or cell size.In conclusion, many factors may be involved in determining the initial adhesion of L. monocytogenes to stainless steel under flow conditions. Two of the main factors are flow rate/shear stress and strain specificity.