Antimicrobial properties of rosin acids-loaded nanoparticles against antibiotic-sensitive and antibiotic-resistant foodborne pathogens

Rosin acids (RA) from coniferous trees are used in folk medicine for healing various skin infections. Despite the antimicrobial potential of RA, their poor solubility in aqueous media may limit their use. In this work RA-loaded polyethylene glycol-poly(lactic-co-glycolic acid) nanoparticles (RA-NPs) with enhanced antimicrobial properties against foodborne bacterial pathogens were produced. RA-NPs were prepared by solvent displacement technique and characterized for relevant colloidal features by dynamic light scattering, laser Doppler anemometry and transmission electron microscopy. Association of RA to NPs occurred with high yields (86% w/w). RA and RA-NPs (~130 nm) were strongly active against antibiotic-sensitive Gram+pathogens, i.e. Clostridium perfringens, Listeria monocytogenes and antibiotic-resistant Staphylococcus aureus. However, both failed in inhibiting the growth of Gram - pathogens (Campylobacter jejuni, Campylobacter coli, Escherichia coli and Salmonella enterica). Association to NPs enhanced the antimicrobial activity of RA. MIC, IC50, IC90, and MBC values of RA-NPs were ten-times lower than RA. RA-NPs did not change the intrinsic toxicity potential of RA. This is the first study on the enhancement of the antimicrobial activity of RA when associated to nanocarriers. This approach may be an effective strategy to produce aqueous-based RA solutions with enhanced antimicrobial activity against antibiotic-sensitive and antibiotic-resistant Gram+pathogens.