Management of Enterococcus faecalis biofilms: a combinatorial approach with phytochemical

The rapid emergence of antimicrobial resistance in Enterococcus faecalis infections was primarily due to their robust biofilm formation, highlighting the urgent need for meaningful strategies. Since combinatorial application of natural phytochemical often offer promising outcomes in dealing with microbial infections, present study indicated the pharmacological, antimicrobial and antibiofilm potential of combinatorial strategies of natural phytochemical involving cuminaldehyde and thymoquinone against E. faecalis. Towards this direction, in silico analysis suggested that both compounds could show favourable oral bioavailability and high GI absorption, with a considerable solubility and drug-likeness profiles. Furthermore, in vitro antimicrobial assay indicated that the minimum inhibitory concentrations (MIC) of cuminaldehyde and thymoquinone were found to be 500 µg/mL and 30 µg/mL, respectively against E. faecalis. Thereafter, the fractional inhibitory concentration (FIC) index score of 0.73 indicated an additive effect prevailed between cuminaldehyde and thymoquinone, enhancing their antimicrobial potential. Thereafter, sub-MIC doses of cuminaldehyde (40 µg/mL) and thymoquinone (8 µg/mL) were selected to assess their antibiofilm potential. Though the compounds were able to show antibiofilm activity separately, their combination was significantly more effective, reduced biofilm formation by approximately 80%, and decreased production of extracellular polymeric substance (EPS) and protein content by ~ 76% and ~ 70%, respectively. Further studies revealed that the antibiofilm activity of the test compounds could likely to be attributed to the accumulation of reactive oxygen species (ROS) and enhancement of membrane permeability. Taken together, all this experimental observation revealed that combination of these natural compounds could potentially improve the treatment outcomes of biofilm-borne infections of E. faecalis.