Inhibition and disruption of bacterial biofilms by a bipyridine-ruthenium complex: a broad-spectrum in vitro study.

Biofilms, communities of microorganisms, are important in the medical and pharmaceutical sectors due to their potential to contaminate medical implants and other equipment. Because their thick matrix makes them resistant to antiseptics, disinfectants, and drugs, biofilms are difficult to eliminate. Therefore, this study investigated the antibiofilm potential of a ruthenium-based complex incorporating the bipyridine ligand CS27. Using the XTT reduction assay, the inhibitory and disruptive effects of CS27 on bacterial biofilms were assessed in vitro for a panel of clinically and industrially relevant bacterial species: Pseudomonas aeruginosa (PAO1), Escherichia coli (ATCC 8739), Listeria monocytogenes (NCTC 11994), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 19433), Listeria innocua (6a) (ATCC 32090), Streptococcus parasanguinis (ATCC 15909), Bacillus cereus (ATCC 10876), and Enterococcus hirae (ATCC 10541). Treatment with 40 µM CS27 substantially inhibited biofilm formation by P. aeruginosa (63.27%), E. coli (92.59%), S. aureus (82.68%), and E. faecalis (95.44%). A higher concentration (65 µM) inhibited biofilm concentration L. innocua (6a) (43.71%) and B. cereus (43.15%). However, CS27 did not significantly inhibit biofilm formation by E. hirae and S. parasanguinis. Disruption assays revealed that the efficacy was determined more by the duration of CS27 exposure than by biofilm maturity. Fluorescence microscopy of cells stained with propidium iodide, and DAPI-CTC confirmed a noticeable reduction in biofilm density in CS27-treated samples compared to untreated controls. Collectively, these findings highlight CS27 as a promising candidate for preventing and disrupting bacterial biofilms.