Synergistic Antibiofilm Effects of Exopolymers Produced by the Marine, Thermotolerant Bacillus licheniformis B3-15 and Their Potential Medical Applications

The exopolysaccharide (EPS B3-15) and biosurfactant (BS B3-15), produced by the marine Bacillus licheniformis B3-15, were recently reported to possess different antibiofilm activities, with the EPS being more active in preventing the adhesion of Pseudomonas aeruginosa and Staphylococcus aureus and the BS in destroying their preformed biofilms on different surfaces. In this study, the synergistic effects of the two exopolymers on the bacterial adhesion and biofilm disruption of P. aeruginosa and S. aureus were evaluated on polystyrene, a medical polyvinyl chloride (PVC) device, and contact lenses (CLs) in order to address their potential use in biomedical applications. To this purpose, EPS B3-15 and BS B3-15 were equally combined (1:1 w/w), and the mixture (BPS B3-15) was added at different concentrations (from 50 to 300 µg mL−1) and at different times of bacterial development. Compared to each polymer, the BPS B3-15 (300 µg mL−1) more efficiently reduced the adhesion of P. aeruginosa and S. aureus on polystyrene (65 and 58%, respectively), PVC devices (62 and 42%, respectively), and CLs (39 and 35%, respectively), also in combination with a CLs care solution (88 and 39%, respectively). Furthermore, BPS B3-15 was able to disrupt mature biofilms, acting more effectively against S. aureus (72%) than P. aeruginosa (6%). The combination of exopolymers at low concentrations exhibited synergistic effects to prevent and eradicate biofilms.