A Combination of the Natural Molecules Gallic Acid and Carvacrol Eradicates P. aeruginosa and S. aureus Mature Biofilms

Wound infection, especially the development of bacterial biofilms, delays wound healing and is a major public health concern. Bacteria in biofilms are more tolerant to antimicrobial agents, and new treatments to eradicate mature biofilms are needed. Combining antimicrobial molecules with different mechanisms of action is an attractive strategy to tackle the heterogeneous nature of microbial communities in biofilms. This study focused on three molecules of natural origin: gallic acid (G), carvacrol (K) and curcumin (Q). Their abilities, individually or in combination, to eradicate biofilms were quantified on mono- and dual-species mature biofilms of <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus,</i> the strains most commonly found in infected wounds. G presented biofilm eradicating activity on <i>P. aeruginosa</i>, whereas K had biofilm eradicating activity on <i>S. aureus</i> and <i>P. aeruginosa</i>. Q had no potent biofilm eradicating activity. The combination of G and K increased the effects previously observed on <i>P. aeruginosa</i> biofilm and led to complete eradication of <i>S. aureus</i> biofilm. This combination was also efficient in eradicating a dual-species biofilm of <i>S. aureus</i> and <i>P. aeruginosa</i>. This work demonstrates that K and G used in combination have a strong and synergistic eradicating activity on both mono- and dual-species mature biofilms of <i>S. aureus</i> and <i>P. aeruginosa</i> and may therefore represent an efficient alternative for the treatment of biofilms in wounds.