Red wines and flavonoids diminish <i>Staphylococcus aureus</i> virulence with anti-biofilm and anti-hemolytic activities

<div><p>The emergence of antibiotic resistant <i>Staphylococcus aureus</i> presents a worldwide problem that requires non-antibiotic strategies. This study investigated the anti-biofilm and anti-hemolytic activities of four red wines and two white wines against three <i>S. aureus</i> strains. All red wines at 0.5–2% significantly inhibited <i>S. aureus</i> biofilm formation and hemolysis by <i>S. aureus</i>, whereas the two white wines had no effect. Furthermore, at these concentrations, red wines did not affect bacterial growth. Analyses of hemolysis and active component identification in red wines revealed that the anti-biofilm compounds and anti-hemolytic compounds largely responsible were tannic acid, <i>trans</i>-resveratrol, and several flavonoids. In addition, red wines attenuated <i>S. aureus</i> virulence <i>in vivo</i> in the nematode <i>Caenorhabditis elegans</i>, which is killed by <i>S. aureus</i>. These findings show that red wines and their compounds warrant further attention in antivirulence strategies against persistent <i>S. aureus</i> infection.</p></div

Inhibition of Pseudomonas aeruginosa and Escherichia coli O157:H7 Biofilm Formation by Plant Metabolite ε‑Viniferin

Pathogenic biofilms are associated with persistent infection due to their high resistances to diverse antibiotics. Pseudomonas aeruginosa infects plants, animals, and humans and is a major cause of nosocomial diseases in patients with cystic fibrosis. In the present study, the antibiofilm abilities of 522 plant extracts against <i>P. aeruginosa</i> PA14 were examined. Three <i>Carex</i> plant extracts at a concentration of 200 μg/mL inhibited <i>P. aeruginosa</i> biofilm formation by >80% without affecting planktonic cell growth. In the most active extract of Carex pumila, resveratrol dimer ε-viniferin was one of the main antibiofilm compounds against <i>P. aeruginosa</i>. Interestingly, ε-viniferin at 10 μg/mL inhibited biofilm formation of enterohemorrhagic Escherichia coli O157:H7 by 98%. Although <i>Carex</i> extracts and <i>trans</i>-resveratrol are known to possess antimicrobial activity, this study is the first to report that <i>C. pumila</i> extract and ε-viniferin have antibiofilm activity against <i>P. aeruginosa</i> and <i>E. coli</i> O157:H7

Anti-biofilm activities of quercetin and tannic acid against <i>Staphylococcus aureus</i>

<div><p> <i>Staphylococcus aureus</i> is a leading cause of nosocomial infections because of its resistance to diverse antibiotics. The formation of a biofilm is one of the mechanisms of drug resistance in <i>S. aureus</i>. The anti-biofilm abilities of 498 plant extracts against <i>S. aureus</i> were examined. Seventy-two plant extracts belonging to 59 genera and 38 families were found to significantly inhibit the formation of biofilms of <i>S. aureus</i> without affecting the growth of planktonic cells. The most active extract, from <i>Alnus japonica</i>, inhibited the formation of biofilms by three <i>S. aureus</i> strains by >70% at 20 μg ml⁻¹. Transcriptional analyses showed that extract of <i>A. japonica</i> repressed the intercellular adhesion genes <i>icaA</i> and <i>icaD</i> most markedly. Quercetin and tannic acid are major anti-biofilm compounds in the extract of <i>A. japonica</i>. Additionally, the extract of <i>A. japonica</i> and its component compound quercetin, reduced hemolysis by <i>S. aureus</i>. This phenomenon was not observed in the treatment with tannic acid. This study suggests that various plant extracts, such as quercetin and tannic acid, could be used to inhibit the formation of recalcitrant biofilms of <i>S. aureus</i>.</p> </div

Diverse plant extracts and <i>trans</i>-resveratrol inhibit biofilm formation and swarming of <i>Escherichia coli</i> O157:H7

<div><p>Infection with enterohemorrhagic <i>Escherichia coli</i> O157:H7 (EHEC) is a worldwide problem. Of the 498 plant extracts screened against EHEC, 16 inhibited the formation of biofilm of EHEC by >85% without inhibiting the growth of planktonic cells, and 14 plant extracts reduced the swarming motility of EHEC. The most active extract, <i>Carex dimorpholepis,</i> decreased swimming and swarming motilities and curli formation. Transcriptional analyses showed that the extract of <i>C. dimorpholepis</i> repressed curli genes, various motility genes, and AI-2 quorum sensing genes, which was corroborated by reduction in the production of fimbria, motility, and biofilm by EHEC. <i>Trans</i>-resveratrol at 10 μg ml⁻¹ in the extract of <i>C. dimorpholepis</i> was found to be a new anti-biofilm compound against EHEC, but importantly, the extract of <i>C. dimorpholepis</i> and <i>trans</i>-resveratrol did not inhibit the fomation of biofilm in four commensal <i>E. coli</i> strains. Furthermore, the extract of <i>C. dimorpholepis</i> decreased the adhesion of EHEC cells to human epithelial cells without affecting the viability of these cells.</p></div