Pure and mixed biofilms formation of Listeria monocytogenes and Salmonella Typhimurium on polypropylene surfaces

Abstract

This study evaluated the capacity of Listeria monocytogenes and Salmonella Typhimurium to form pure and mixed biofilms on polypropylene surface and analyzed the expression of genes related to biofilm formation within 24 h and 120 h. The planktonic and sessile growth of L. monocytogenes and S. Typhimurium were related to incubation temperature. There was no statistical difference between the total population not only in pure L. monocytogenes and pure S. Typhimurium biofilms, but also in mixed biofilms at 12 °C and 37 °C. Pure and mixed biofilms were able to maintain viable cells for 3000 h at 10 °C with counts greater than when incubated for 120 h, with a greater population increase in mixed biofilms. Regarding the 24 h and 120 h biofilms of L. monocytogenes in both pure and mixed conditions at 12 °C and 37 °C, we were able to find expression of prfA, agrB, agrC and agrD genes. Concerning S. Typhimurium biofilms, we found expression of agfA, adrA and csgD genes in all situations evaluated, except for mixed S. Typhimurium biofilm at 12 °C for 24 h. This article documents the ability of L. monocytogenes and S. Typhimurium to form mixed biofilms and suggests that these two microorganisms may act synergistically.