Patterns of Biofilm Formation by Members of Listeria, Salmonella, and Pseudomonas at Various Temperatures and the Role of Their Synergistic Interactions in the Formation of Biofilm Communities

Biofilm formation on abiotic surfaces in the food industry is a major public health problem. Indeed, biofilms represent a constant source of pathogens, such as Listeria monocytogenes and bacteria of the genus Salmonella. Formation of multispecies biofilms by pathogens and spoilage microorganisms significantly contributes to the persistence of microorganisms in meat processing plant environments and thus poses a serious risk for product safety. In this study, 46 strains of microorganisms isolated from food products and various elements of food industry environment were tested for their ability to form biofilms at different temperatures. The analyzed pathogenic strains (Listeria monocytogenes and Salmonella sp.) and spoilage microorganisms (Pseudomonas sp.) exhibited adhesion to abiotic surfaces with subsequent formation of persistent biofilms. Low positive temperature was not a limiting factor in their ability to form biofilms. After 24 h of incubation at 4°C, Listeria and Salmonella sp. developed stable biofilms. It was found that these bacteria were capable of forming biofilms on various abiotic surfaces present in the meat industry (ceramic tiles, glass, and plastic). Analysis of synergistic interactions among members of the genera Listeria, Salmonella, and Pseudomonas in the formation of mixed biofilms at 4°C showed that combinations of a pathogenic microorganism and a Pseudomonas member formed biofilms significantly more efficiently than combinations of two pathogens. This indicates the importance of Pseudomonas species in synergistic interaction among microorganisms.