Plant Monoterpenes Geraniol, Eugenol and Carvacrol Against Multidrug-Resistant ESKAPE Isolates from Surgical Wounds

Objectives: The study determined antibiotic resistance profiles of surgical wound’ multidrug-resistant (MDR) isolates belonging to the ESKAPE group and evaluated antibacterial and antibiofilm activities of geraniol (G), carvacrol (C), and eugenol (E), individually and in the selected binary mixtures against them. The cytotoxicity of monoterpenes and their combinations was also assessed. Methods: The antibacterial activity against E. faecium, S. aureus MRSA, K. pneumoniae, A. baumannii, P. aeruginosa and Enterobacter spp. was assessed in microdilution assay. Antibiofilm activity was tested in crystal violet assay. Cytotoxicity of the tested monoterpenes was estimated in XTT assay. Results: C proved the strongest antimicrobial activity (MIC 0.32±0.24 mg mL-1). Antibacterial checkerboard assay, used to study interactions, showed synergism between all monoterpenes. Significant biofilm inhibition (in crystal violet assay) was found for sole monoterpenes, with the most pronounced inhibition for G (38.78–84.72%, p< 0.05). The most significant biofilm eradication was demonstrated for C (25.21-61.34%, p< 0.05), while the G (28.83-55.26%) and E (21.74-52.83%) exhibited a weaker effect. G-C mixtures were further studied for the antibiofilm effect, showing notable inhibition of biofilm formation on all isolates except P. aeruginosa. However, the G-C mixtures exhibited biofilm eradication activity solely against P. aeruginosa. Cytotoxicity tested on normal human MRC-5 fibroblasts showed no cytotoxicity at tested doses of G, E and C, while G-C mixtures were less cytotoxic than povidone-iodine (p< 0.05), used as control. Conclusions: All monoterpenes and G-C mixture proved significant antibacterial and antibiofilm potential against ESKAPE isolates, and acceptable impact on cell viability.