Paper AS+BI+NS-TuM5
Surface Characteristics of Listeria Monocytogenes Mutants with Variable Pathogenicity Levels

Tuesday, October 16, 2007, 9:20 am, Room 610

Despite being an important food-borne pathogen, L. monocytogenes in fact comprises a diversity of strains with varying virulence. Whilst many strains of L. monocytogenes have pathogenic potential and can result in disease and mortality, others have limited capability of establishing infections and relatively avirulent. Although very important, the question of how the composition of the bacterial surface and the properties of bacteria vary between strains that have different level of virulence at the molecular level needs to be answered. To answer this question, interaction forces between five different L. monocytogenes mutants that vary in their virulence and a model surface of silicon nitride were investigated using atomic force microscopy (AFM). Adhesion measurements between the strongest Listeria mutant and silicon nitride reveled that although both surface polysaccharides and surface proteins contributed significantly to the total adhesion, polysaccharides contribution (1.0 ± 0.2 nN) was larger than that of proteins’ contribution(0.38 ± 0.1 nN). Adhesion forces were also dependent on the pH value of the solution, temperature, and media type. Experiments on intermediate virulence mutants and avirulent mutants are currently ongoing. Successful completion of these experiments will improve our understanding of the main molecular differences between virulent and avirulent strains of L. monocytogenes. Such findings would be very important, because it will allow for the first time and at a molecular level, to define a criteria that can distinguish virulent L. monocytogenes’ strains from avirulent ones and therefore reduce unnecessary recalls of food products and help in preventing disease outbreaks.