Mono- and Mixed-Species Biofilm Formation by Salmonella Infantis, Salmonella Kentucky, Enterococcus faecium, and Enterococcus faecalis

It is crucial to understand the interactions between food-borne pathogens, as they are commonly encountered as multi-species biofilms in the food industry. Since Salmonella and Enterococcus are both found in poultry intestinal micro-biota, the multi-species biofilms of these strains gain more significance. This study aimed to reveal the synergistic and antagonistic effects of mono- and mixed-species biofilms of Salmonella Infantis, Salmonella Kentucky, Enterococcus faecium, and Enterococcus faecalis on each other. Biofilm formation of mono- and mixed-species at different concentrations (10(9), 10(7), 10(5), and 10(3) cfu/mL) were determined in Tryptic Soy Broth using polystyrene microplates at room temperature (21 +/- 1 degrees C) for 48 hours. According to the optical density measured at 590 nm, S. Infantis was determined as a strong biofilm producer, and S. Kentucky and E. faecium were defined as weak biofilm producers under the conditions applied in the study. No biofilm formation was observed in E. faecalis. In addition, while S. Infantis and S. Kentucky exhibited an antagonistic effect on each other when co-incubated, a synergistic effect was seen between the S. Infantis and Enterococcus spp. This study highlights the impact of microbial interactions in mixed-species biofilm formed by foodborne pathogens, and could help in future studies on combating biofilms, especially in poultry-based food processing environments.