Introduction Biofilms formed by pathogenic bacteria such as Staphylococcus aureus and Escherichia coli pose a significant threat to public health. Combination therapy has emerged as a promising strategy to combat bacterial infections and biofilm formation. In this study, the natural product perillaldehyde and the surfactant domiphen were evaluated for their ability to inhibit biofilm formation by these pathogenic strains. Methods The antimicrobial activity of perillaldehyde and domiphen, alone and in combination, was assessed against S. aureus and E. coli strains. Synergism was determined by calculating the fractional inhibitory concentration index. Biofilm mass was evaluated using the crystal violet staining assay, and the viability of biofilm cells on stainless steel and polyethylene surfaces was examined via viable cell counting. Additionally, the therapeutic potential of the combination was further assessed using a Galleria mellonella larval infection model. Results The combination of perillaldehyde and domiphen showed synergistic effects against both pathogenic strains, with a fractional inhibitory concentration index of less than 0.36. The combination of 1 μL/mL perillaldehyde and 1 μg/mL domiphen dispersed more than 53% of the biofilm mass in both S. aureus and E. coli strains. In addition, the combination reduced the total viable bacterial counts in biofilms on stainless steel and polyethylene surfaces by approximately 103 CFU/mL. The treatment also significantly improved the survival rate of G. mellonella larvae infected with the bacteria. Discussion These results indicate that the novel combination of perillaldehyde and domiphen has the potential to decrease biofilm formation on various industrial material surfaces.
Qiao et al. (Tue,) studied this question.