Hydrodynamic shear stress to removeListeria monocytogenesbiofilms from stainless steel and polytetrafluoroethylene surfaces

Abstract

To calculate the shear stress needed to remove sessile Listeria monocytogenes cells from stainless steel (SS) and polytetrafluoroethylene (PTFE) surfaces. Listeria monocytogenes biofilms were formed on SS and PTFE surfaces. Shear stress was calculated using a radial flow chamber device and cells quantified by staining with 4',6-diamidino-2-phenylindole. Results showed that shear stress between 24 and 144 N m(-2) removed up to 98% of cells from SS surfaces. PTFE presents a very hydrophobic surface, and a significant lower removal (P < 0.05) of only 63% was achieved; moreover, on PTFE discs, detachment of L. monocytogenes biofilms was more efficient at a lower shear stress (between 8.6 and 34 N m(-2) ). Water flow is more effective in removing L. monocytogenes biofilms from SS surfaces than from PTFE materials. This work clearly demonstrates that water flow does not have the same efficiency in removing cells from different material surfaces and shows the need to optimize cleaning and sampling procedures by considering the conditions in which cells attach to surfaces and the physicochemistry of the surfaces.