aureus. The results show that

farrerol significantly decreased, in a dose-dependent manner, the production of α-toxin by both methicillin-sensitive S. aureus and methicillin-resistant S. aureus. Staphylococcus aureus is a significant opportunistic pathogen that leads to a variety of infections. Treating such infections has been complicated by the widespread prevalence of methicillin-resistant S. aureus (MRSA) isolates. Therefore, there is an urgent need to develop novel and potent antimicrobial agents to treat life-threatening infections caused by MRSA strains. Farrerol (Fig. 1) is a traditional Chinese check details medicine that has been commonly used as an antibechic. Additionally, farrerol exerts multiple biological activities, including anti-inflammatory, antibacterial and antioxidant activity for scavenging radicals and inhibiting a variety of enzymes (Zhu et al., 2007). However, to our knowledge, no studies have focused on its effects on S. aureus. In the present study, the anti-S. aureus activity of farrerol was evaluated, and the influence of subinhibitory concentrations of farrerol on α-toxin production by both methicillin-sensitive S. aureus (MSSA) and MRSA was determined. MSSA strain ATCC 29213 was obtained from the American Type Angiogenesis inhibitor Culture Collection

(ATCC). Thirty-four S. aureus isolates, 14 MSSA and 20 MRSA (17 vancomycin-sensitive S. aureus and three vancomycin-intermediate S. aureus), were acquired from clinical samples at the First Hospital of Jilin University. These strains belong to four distinct pulsed field gel electrophoresis types. The clinical MRSA strains 2985 and 3701, which have the property to produce α-toxin, were subjected to further experimentation. Mueller–Hinton broth

(MHB) was purchased from BD Biosciences Inc. (Sparks, MD). Farrerol (purity≥98%), oxacillin, vancomycin, gentamicin, erythromycin, clindamycin, tetracycline and ciprofloxacin were obtained from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China), and stock solutions selleck chemicals llc of different concentrations were prepared in dimethyl sulphoxide (DMSO) (Sigma-Aldrich, St. Louis, MO). Lipopolysaccharide (Escherichia coli 055:B5) and 3-(4,5-dimethylthiazol-2-y1)-2,5-diphenyl-tetrazolium bromide (MTT) were purchased from Sigma-Aldrich. Dulbecco’s modified Eagle’s medium (DMEM) and fetal bovine serum (FBS) were obtained from Invitrogen-Gibco (Grand Island, NY). The RAW264.7 mouse macrophage cell line was purchased from the China Cell Line Bank (Beijing, China). Cells were cultured in DMEM supplemented with 3 mM glutamine, antibiotics (100 U mL−1 penicillin and 100 U mL−1 streptomycin) and 10% heat-inactivated FBS. Cells were mechanically scraped, seeded in 96-well plates at 4 × 105 cells mL−1; following the addition of different concentrations of farrerol (4–32 μg mL−1), the macrophages were incubated in a 37 °C, 5% CO2 incubator for 48 h.