Purpose: The objective of this study was the characterization of the biofilm formation of S. macedonicus under monospecies and dual-species (with foodborne pathogens) conditions. The foodborne pathogens studied were Staphylococcus aureus and Salmonella enterica serotype Typhimurium.
Methods: Biofilm formation was studied on stainless steel coupons, which were initially incubated (15°C, 3 h) in mono- or dual-species bacterial suspensions (in Ringer’s solution) to allow for bacterial attachment. Then, coupons carrying strongly attached bacteria were transferred in brain heart infusion broth, and were further incubated at 37°C for 72 h or at 15°C for 144 h. Biofilm bacterial populations were determined at 3 h (attachment), and at 24-h and 48-h intervals during incubation at 37°C and 15°C, respectively.
Results: Co-culture with S. aureus (15°C) and S. Typhimurium (15, 37°C) significantly increased the biofilm-forming ability of S. macedonicus compared to its monoculture counterparts, while its biofilm populations in the mixed cultures at the end of the incubation periods were also considerably higher (p<0.05) than those of the pathogens. However, the presence of S. macedonicus in dual-species cultures did not appear to affect (p≥0.05) the biofilm formation behavior of either of the studied foodborne pathogens (relative to that observed under monospecies conditions).
Significance: Research data on the behavior of lactic acid bacteria within multispecies biofilm communities, along with corresponding data on the in situ production of antimicrobial and/or signaling compounds, are expected to be of great value from a microbial food ecology perspective.