Oleoresin from copaifera martii hayne: in vitro antibacterial activity against planktonic and biofilm cells of vancomycin-resistant enterococcus faecium

Enterococcus faecium is one of the major causative agents of healthcare-associated infections worldwide. This bacterium exhibits a remarkable capacity of acquiring new determinants of resistance, including to the last resort antimicrobials. The present study reports the in vitro antibacterial effect of Copaifera martii Hayne oleoresin against vancomycin-resistant E. faecium strains and E. faecium ATCC6965, a vancomycin-susceptible strain. Oleoresin inhibited the growth of planktonic cells, displaying a minimal inhibitory concentration (MIC) of 0.060 mg/mL for most strains. Time-kill kinetics revealed that this oleoresin exhibited a bactericidal activity against planktonic cells. MIC of kaurenoic acid, a diterpene present in C. martii oleoresin, ranged from 0.025 to 0.050 mg/mL, indicating that this substance seems to be one of the active components of C. martii oleoresin related to the antibacterial activity against E. faecium. A significant reduction in metabolic activity and biomass of established biofilms of E. faecium strains was observed after treatment with MIC and 2xMIC of oleoresin. The oleoresin did not display in vitro toxicity to mammalian cells at concentrations that were effective in killing planktonic and biofilm cells of E. faecium. These results indicate the potential of C. martii oleoresin for the development of new control strategies for E. faecium infections.