Comparison study between gallic acid and curcumin extracts on the efflux pump inhibition of clinically isolated staphylococcus aureus

Abstract

Background. The increasing incidence of multidrug-resistant bacteria has forced the development of novel techniques to improve antibiotic potency. Bacterial efflux pumps are essential in this resistance as they actively expel detrimental antimicrobial substances from the cell. Aim. This study aimed to examine the inhibitory effects of two plant extracts, gallic acid and curcumin, on the efflux pump activity of clinically isolated Staphylococcus aureus. Methods. The efficacy of different concentrations (100, 200, 400, 800, and 1600 mg/ml) of gallic acid and curcumin extracts was assessed. Cartwheel assays were conducted to evaluate efflux activity before and after treatment, and real-time PCR (qRT-PCR) was utilized to confirm the genetic impact of these extracts on the norA gene encoding the efflux pumps. Results. The findings indicated substantial decreases in resistance levels and significant inhibition of efflux pump activity, with 400 mg/ml identified as the lowest effective concentration. While curcumin demonstrated a more potent zone of inhibition in growth assays, real-time PCR results revealed that gallic acid was significantly more effective than curcumin in downregulating and inhibiting the expression of the norA gene across the tested concentrations (fold change of 0.60 vs 0.66, respectively). Conclusion. Both gallic acid and curcumin possess significant potential as plant-derived efflux pump inhibitors (EPIs). However, gallic acid demonstrates superior efficacy in downregulating norA gene expression, underscoring its potential as a more effective agent in modifying gene-mediated resistance in multidrug-resistant Staphylococcus aureus strains.