Biofilm formation by Salmonella spp. and Listeria monocytogenes on plastic surface

Aims: To investigate the biofilm formation by 122 Salmonella spp. and 48 Listeria monocytogenes strains on a plastic surface. Methods: Quantification of biofilm formation was performed in brain heart infusion (BHI), trypcase soya broth (TSB), meat broth (MB) and 1/20 diluted trypcase soya broth (1/20-TSB) in plastic microtitre plates. Results: All tested Salmonella spp. and L. monocytogenes strains produced biofilm in a suitable medium. However, the quantities of biofilm produced by Salmonella spp. were greater than those produced by tested L. monocytogenes strains. The nutrient content of the medium significantly influenced the quantity of produced biofilm. Diluted TSB was the most effective in promoting blofilm production by Salmonella spp., followed by TSB, while the least quantity of biofilm was formed in BHI and MB. L. monocytogenes produced the highest quantities of biofilm in BHI, followed by TSA, then MB, and the least quantities of biofilm were produced in 1/20-TSB. Conclusions: Salmonella spp. produces more biofilm in nutrient-poor medium, while L. monocytogenes produce more biofilm in nutrient-rich medium.