Synergistic anti–Staphylococcus aureus activity of amoxicillin in combination with Emblica officinalis and Nymphae odorata extracts

To evaluate the antibacterial activity of Emblica officinalis Gaertn (E. officinalis; Family: Euphorbiaceae) seed and Nymphae odorata Aiton (N. odorata; Family: Nymphaeaceae) stamen extracts, alone and in combination, and in combination with amoxicillin (Ax) against Staphylococcus aureus (S. aureus). Antibacterial activity of ethanolic extracts of amla, E. officinalis, seed (AMS; 500 μg) and sapla, N. odorata, stamen (SAP; 500 μg) for 12 methicillin-resistant S. aureus (MRSA) isolates was determined following agar diffusion; in order to assess the combined antibacterial activity, AMS (250 μg) plus SAP (250 μg) were considered. The Ax (10 μg) activity alone and in combination with AMS (250 μg), and SAP (250 μg) was determined by disk diffusion. The zone diameters of inhibition (ZDI s) for the agents were recorded, and growth inhibitory indices (GII s) were calculated. The MRSA isolates (n = 12) had AMS (500 μg) and SAP (500 μg) ZDI s of 12-19 mm and 21-24 mm, respectively. The ZDI s (range 24-27 mm) increased by 3-4 mm due to combined action of AMS (250 μg) and SAP (250 μg) indicating synergy between extracts for MRSA (GII 0.634-0.742). The MRSA isolates were resistant to Ax (ZDI: 8-11 mm), which in combination with AMS and SAP had synergistic effect, both due to increased ZDI mean± SD = (3.5 ± 0.577) mm and GII (0.631-0.894). The data suggest that the plants, E. officinalis and N. odorata alone or in combination, are promising in the development of phytomedicines, which may be used, alone or in combination with the antibiotic, Ax, against MRSA infection.