Anti-biofilm properties of Portuguese honeys against multi-drug resistant microorganisms: A promising strategy for chronic wounds healing

Honey is considered a promising strategy for chronic wound management, being a possible solution for bacterial resistance problem mostly due to its physical-chemical features. However, these properties might vary significantly depending on the honey floral source. Dark-colored honey, such as chestnut honey, is related to increased antioxidant and bactericidal properties. This study aims to assess biofilms of multidrug-resistant microorganisms in honey samples from the Natural Park of Montesinho, in Portugal, which is considered a region with predominant chestnut floral source. The minimum inhibition concentration (MIC) of honey was tested for Staphylococcus aureus , Escherichia coli, Klebsiella pneumoniae , Pseudomonas aeruginosa , and Candida albicans . The biofilm removal as well as the metabolic inactivation of the biofilms were evaluated using three honey concentrations: 1xMIC, 5xMIC, and 10xMIC. The biofilm viability was analyzed with fluorescent microscopy. Honey samples were characterized according to the pollen profile, phenolic composition, H 2 O 2 levels, tyrosinase inhibition, and pH. The antioxidant capacity was determined through FRAP and ABTS assays. Most of the honey samples exhibited a MIC of 6.75%. Biofilm removal efficacy differs among samples. Regression analysis evidenced a positive correlation between the biofilm removal and concentrations of H 2 O 2 , vanillic acid , pinocembrin , Cytisus striatus and Corrigiola telephiifolia, and pH. The honey concentration of 10xMIC was the most effective to inhibit the biofilm metabolism and viability. The concentrations of C. sativa , H 2 O 2 , and the anti-tyrosinase and FRAP activities were also positively correlated. The honey samples had a dominant presence of Castanea sativa pollen and were effective against biofilms formed by multidrug-resistant microorganisms.