Inhibitory effect of the brown seaweed Sargassum angustifolium extract on growth and virulence factors of Staphylococcus aureus

Regarding the growing trend of multi-drug resistant strains of Staphylococcus aureus, the search for alternative and novel antimicrobial agent has been intensified. For this purpose, the present study was carried out to investigate the antagonistic effect of the brown seaweed Sargassum angustifolium on growth and virulence factors of S. aureus. A typical microdilution assay was performed to monitor inhibitory effect of the seaweed extract on growth of the bacteria within a 6-h period. Furthermore, Real-Time PCR assay with specific primers was conducted to evaluate the impact of seaweed extract on expression of the genes encoding staphylococcal enterotoxins (sea) and capsule formation (cap8). The results obtained in this research revealed that S. angustifolium extract inhibited bacterial growth in a dose-dependent way; so that bacterial growth was fully stopped at the end of the assay. Antibacterial effect was enhanced by increase in seaweed extract concentration. The results of Real-Time PCR assay indicated that the seaweed extract was able to decrease virulence genes expression significantly. Again, by increase in seaweed extract concentration, stronger inhibitory effect was observed. As a whole, the findings of this study suggest that S. angustifolium extract has potent antimicrobial effect that can be used for development of new generation of anti-staphylococcal medicines.