Comparison of antivirulence activities of black ginseng against methicillin-resistant staphylococcus aureus according to the number of repeated steaming and drying cycles

Korean ginseng has been widely used in Eastern medicine for thousands of years. The contents of the compounds in ginseng roots change depending on the amount of steaming and dry-ing, and the drying method used. Black ginseng (BG) is the Korean ginseng processed by repeated steaming and drying. In this study, 5-year-old fresh Korean ginseng roots were steamed and dried 3 or 5 times, and we investigated how many cycles of steaming and drying are preferable for anti-virulence activities against methicillin-resistant Staphylococcus aureus (MRSA). As a result, the anti-virulence activities was increased by the treatment of BG that was steamed and dried three times, and the effect was further increased by five-time processed BG. Moreover, an ELISA showed that the TNF-α production of RAW264.7 cells stimulated by MRSA supernatants was inhibited by sub-inhibitory concentrations of BG extract. The expression of Hla, staphylococcal enterotoxin A (SEA), and staphylococcal enterotoxin B (SEB), an important virulence factor in the pathogenicity of MRSA, was found to decrease when bacterial cells were treated with BG extract. The antivirulence activities of BG were not simply due to pathogen growth inhibition; the BG extract was shown to decrease agrA, hla, sea, and seb expression in MRSA. Therefore, BG strongly reduces the secretion of the virulence factors produced by Staphylococcus aureus, suggesting that a BG-based structure may be used for the development of drugs aimed at staphylococcal virulence-related exoproteins. This study suggests that BG could be used as a promising natural compound in the food and pharmaceutical industry.