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 Pseudomonas aeruginosa and Staphylococcus aureus, the strains most commonly found in infected wounds. G presented biofilm eradicating activity on P. aeruginosa, whereas K had biofilm eradicating activity on S. aureus and P. aeruginosa. Q had no potent biofilm eradicating activity. The combination of G and K increased the effects previously observed on P. aeruginosa biofilm and led to complete eradication of S. aureus biofilm. This combination was also efficient in eradicating a dual-species biofilm of S. aureus and P. aeruginosa. 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 S. aureus and P. aeruginosa and may therefore represent an efficient alternative for the treatment of biofilms in wounds.

Macrophages participate in cutaneous wound healing by adopting M1 pro-inflammatory and M2 immunoregulatory/pro-repair phenotypes. Chronic wounds associated with a deficient macrophage response could benefit from treatments that restore an acute inflammatory response and promote healing. Calcium-alginate dressings release calcium ions, which are potent bioactivators of macrophage function in wounds. Here, the effects of two calcium-alginate dressings, Algosteril^® (ALG, pure Ca²⁺ alginate) and Biatain^® Alginate (BIA, Ca²⁺ alginate with carboxymethyl cellulose), and a 3 mM CaCl₂ solution were compared in human macrophages polarized to M1 or M2. ALG and CaCl₂ preserved monocyte viability, and BIA reduced it. Both alginates and CaCl₂ reinforced the M1 pro-inflammatory transcriptional profile and phenotype, with significant increases in IL-6 and TNF-α secretion by ALG only. In M2 macrophages, all conditions increased the M1-specific gene expression and reduced M2 markers, suggesting an orientation toward an inflammatory profile. Only ALG significantly increased the secretion of CCL18 and VEGF, suggesting pro-repair activity. All conditions increased M2 phagocytic activity. This work demonstrates the interest in calcium alginates for stimulating macrophage subtypes, which could help restore wound healing, especially in patients with compromised innate immunity. It highlights the differences among the calcium-alginate dressings. The pure alginate shows higher stimulation of macrophage pro-inflammatory and pro-repair functions.

Early after skin wounds, innate immune cells, including natural killer (NK) cells, infiltrate the wound bed within the first 24 hours. The applic | POSTER