Adsorption, attachment and biofilm formation among isolates of Listeria monocytogenes using model conditions

Aims: To determine whether isolates of Listeria monocytogenes differ in their ability to adsorb and form biofilms on a food-grade stainless steel surface. Methods and Results: Strains were assessed for their ability, to adsorb to a test surface over a short time period. Although some differences in numbers of bound cells were found among the strains, there were no correlations between the degree of adsorption and either the serotype or source of the strain. The ability of each strain to form a biofilm when grown with the test surface was also assessed. With the exception of a single strain, all strains adhered as single cells and did not form biofilms. Significant differences in adherence levels were found among strains. Strains demonstrating enhanced attachment produced extracellular fibrils, whereas those which adhered poorly did not. A single strain formed a biofilm consisting of adhered single cells and aggregates of cells. Conclusions: Significant differences were found in the ability of various L. monocytogenes strains to attach to a test surface. In monoculture, the majority of strains did not form biofilms. Significance and Impact of the Study: Differences in attachment and biofilm formation among strains provide a basis to study these characteristics in L. monocytogenes.