Eleutheroside K Isolated from Acanthopanax henryi (Oliv.) Harms Inhibits the Expression of Virulence-Related Exoproteins in Methicillin-Resistant Staphylococcus aureus

Inhibiting Staphylococcus aureus Virulence Factors: Advances in Traditional Chinese Medicines and Active Compounds

Staphylococcus aureus is one of the most prevalent antibiotic-resistant bacteria, characterized by high morbidity and mortality. The pathogenicity of S. aureus relies on the production of multiple virulence factors. In recent years, antivirulence strategies have shown promise in developing antiinfective drugs by targeting the inhibition of bacterial virulence factors rather than directly killing pathogens. In Asia, some traditional Chinese medicines have a long history of antiinfective application and have demonstrated therapeutic efficacy. However, their antiinfective mechanism has not been fully elucidated. Recent studies have revealed that numerous extracts of TCM, as well as pure compounds from TCM, significantly inhibited the expression of virulence factors of S. aureus, which might be one of their antiinfective mechanisms with potential for the development of novel antiinfective agents. In this review, we summarized the major virulence factors of S. aureus and recent advances in TCM-derived antivirulence agents, including TCM formulae, single herbs, and isolated bioactive compounds, which showed antivirulence capability against S. aureus. Investigating the antivirulence mechanism of TCM not only enhances our understanding of TCM's antiinfective mechanisms but also facilitates the isolation of active compounds with therapeutic potential against S. aureus infection.

Characteristic Analysis of Soil-Isolated Bacillus velezensis HY-3479 and Its Antifungal Activity Against Phytopathogens

During the investigation of beneficial agricultural microorganisms, a novel Bacillus strain was isolated. To isolate an effective microorganism that has antifungal activity, soil samples were collected from an agricultural field in the southern area of Pohang, Korea. One strain that had specificity on plant pathogens was analyzed. According to 16S rRNA sequencing, the isolated bacterium was identified as Bacillus velezensis and was designated as HY-3479. Few assays were taken to analyze the characteristics of the HY-3479 strain. In agar plate assay, HY-3479 showed antifungal effects on Colletotrichum acutatum, Cylindrocarpon destructans, Rhizoctonia solani, and Sclerotinia sclerotiorum. The strain also had various enzymatic activities including protease, amylase, and β-1,3-glucanase, which were relatively higher than control strains. Metabolites study of strain HY-3479 was conducted by GC-MS analysis and the bacterium contained many plant growth promoters like 3-methyl-1-butanol, (R, R)-2,3-butanediol, acetoin, and benzoic acid which were not found in untreated TSB medium. In gene expression analysis, antifungal lipopeptide genes like srfc (surfactin) and ituD (iturin A) were highly produced in the HY-3479 strain compared to the control strain KCTC 13417. B. velezensis strain HY-3479 may be the candidate to be an effective microorganism in agriculture and become a beneficial biocontrol agent with plant growth-promoting activities.

Synergistic Antibacterial Activity with Conventional Antibiotics and Mechanism of Action of Shikonin against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a troublesome pathogen that poses a global threat to public health. Shikonin (SKN) isolated from Lithospermum erythrorhizon (L. erythrorhizon) possesses a variety of biological activities. This study aims to explore the effect of the combined application of SKN and traditional antibiotics on the vitality of MRSA and the inherent antibacterial mechanism of SKN. The synergies between SKN and antibiotics against MRSA and its clinical strain have been demonstrated by the checkerboard assay and the time-kill assay. The effect of SKN on disrupting the integrity and permeability of bacterial cell membranes was verified by a nucleotide and protein leakage assay and a bacteriolysis assay. As determined by crystal violet staining, SKN inhibited the biofilm formation of clinical MRSA strains. The results of Western blot and qRT-PCR showed that SKN could inhibit the expression of proteins and genes related to drug resistance and S. aureus exotoxins. SKN inhibited the ability of RAW264.7 cells to release the pro-inflammatory cytokines TNF-α and IL-6, as measured by ELISA. Our findings suggest that SKN has the potential to be developed as a promising alternative for the treatment of MRSA infections.