The bacterial adhesion can be controlled (inhibit or promote) by different material surface characteristics like surface roughness, on which we concentrate in our study. Four different glass surfaces were prepared by polishing the glass plates with different gradations. The corresponding surface roughness was controlled by atomic force microscope and profilometer. For experiments we have used one Gram-positive bacterium (Staphylococcus aureus) and two Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli).The rate of adhered bacteria on glass surfaces was determined spectrophotometrically. The results showed that the rate of adhered bacteria increases with increasing surface roughness. The increased adhesion of bacteria on more rough surfaces is the interplay between the increasing effective surface and increasing number of defects on the surface. In order to keep all parameters under control we have also measured the surface charge density and hydrophobicity of bacteria and glass surfaces as well.
The contribution outlines the scientific cooperation with the Chair of Biotechnology, Biotechnical Faculty, University of Ljubljana. The collaboration started one year ago with the applicative project entitled “Microbial adhesion management on material surfaces“. In this project the researchers from the following institutions are included: Faculty of Health Sciences, Biotechnical Faculty and Veterinary Faculty, University of Ljubljana, Institute “Jožef Stefan”, and Iskra Pio, d.o.o. Within this project we study interactions between microorganisms and material surfaces. The objective of this study is to investigate the influence of surface roughness and hydrophobicity on the degree of microorganism adhesion. In the first part the scientific background will be stated and the project will be described. Importance of this research on the food safety strategy in primary production will be given. We will conclude with the message for the future.
The ability of bacteria to attach to the food contact surface and to form biofilm is one of the important hazards in production of safe food. Given the tremendous clinical importance of biofilms, it is somewhat surprising that there is no standard method for investigating the cells in bacterial biofilms. For bacteria, a common method is to quantitate the mass of biofilms by crystal violet or safranin staining, followed by extraction of bound dye with a solvent and measurement of absorption. Simple and rapid methods which provide information about viability are required for an effective control and operation of the biofilm systems. Tetrazolium salts have become some of the most widely used tools in cell biology for measuring the metabolic activity of microorganisms and depend on the reduction produces of dye in living cells, that can be used for quantitative redox assays. The goal was to optimize several spectrophotometric methods to broaden their applicability for biofilm quantification. We tested tetrazolium dyes MTT, XTT, TTC and INT as indicators of cell metabolism and their application in biofilm quantification. We included also a microdilution method based on ATP bioluminescence measurement and resazurin fluorescence measurement which were previously found to be useful, rapid techniques for determining antibacterial efficiency. Assays were optimised and compared as quantitative methods of measuring bacterial viable cells on polystyrene surface.