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

Objective: To evaluate the antibacterial activity of Emblica officinalis Gamin (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). Methods: Antibacterial activity of ethanolic extracts of amla, E. officinalis, seed (AMS; 500 mu g) and sapla, A odorata, stamen (SAP; 500 mu g) for 12 methicillin-resistant S. aureus (MRSA) isolates was determined following agar diffusion; in order to assess the combined antibacterial activity, AMS (250 mu g) plus SAP (250 mu g) were considered. The Ax (10 mu g) activity alone and in combination with AMS (250 mu g), and SAP (250 mu g) was determined by disk diffusion. The zone diameters of inhibition (ZDIs) for the agents were recorded, and growth inhibitory indices (GIIs) were calculated. Results: The MRSA isolates (n=12) had AMS (500 mu g) and SAP (500 mu g) ZDIs of 12-19 mm and 21-24 mm, respectively. The ZDIs (range 24-27 mm) increased by 3-4 mm due to combined action of AMS (250 mu g) and SAP (250 mu g) 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). Conclusions: 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.