SYNERGISTIC EFFECT OF (S)-CIS-VERBENOL WITH THE ANTIBIOTICS AMOXICILLIN AND GENTAMICIN AGAINST SENSITIVE AND RESISTANT STAPHYLOCOCCUS AUREUS STRAINS

The synergistic activity among the monoterpene (S)-cis-Verbenol and the antibiotics Amoxicillin and Gentamicin were evaluated against a sensitive and a resistant strain of Staphylococcus aureus, is the last one also resistant to methicillin (MRSA). The combinations were evaluated by the checkerboard method. The combinations of both antibiotics with the terpene showed synergic effects for the MRSA strain, whereas for the sensitive strain one combination showed synergy with amoxicillin and additionally one combination showed the additive effect with Gentamicin. To confirm the observed results, the combination that had the lowest concentration of Amoxicillin and the monoterpene were assayed by the time-kill curve method. An even lower concentration of the terpene that did not show cytotoxicity against human cells was also assayed. The results obtained confirmed those of the checkerboard method and synergy was also observed for the non-cytotoxic concentration of (S)-cis-Verbenol analyzed. This opens interesting possibilities about the use of purely natural products in combination with antibiotics to treat infections produced by sensitive and resistant bacteria.