Introduction. The increasing resistance and the pathogen’s complex multi-drug resistance mechanisms made the selection of effective antimicrobial treatments more challenging for Pseudomonas aeruginosa ( P. aeruginosa ). The study aimed to explore the effect of Scutellaria baicalensis , Prunella vulgaris and antimicrobial peptide LL-37 on the virulence factors of P. aeruginosa . Hypothesis. Previous studies have shown that extracts from traditional Chinese medicines, Scutellaria baicalensis and Prunella vulgaris , can also enhance the effects of antibiotics and reduce antibiotic resistance in P. aeruginosa . Antimicrobial peptide LL-37 shows the potential as a new-generation candidate for treating multi-drug-resistant bacteria, which has advantages over traditional antibiotics, whilst the combination role between Scutellaria baicalensis , Prunella vulgaris and LL-37 in P. aeruginosa remains unknown. Aim. We explored whether the combined use of Scutellaria baicalensis , Prunella vulgaris and LL-37 can exert antibacterial effects through the quorum sensing (QS) system. Methodology. The minimal inhibitory concentrations of Scutellaria baicalensis , Prunella vulgaris and LL-37 were determined for PAO1 and PA-ΔlasI/rhlI using micro broth dilution. The antibacterial activity of Scutellaria baicalensis combined with LL-37 and Prunella vulgaris combined with LL-37 was also assessed. The growth abilities of PAO1 were analysed after being treated with Scutellaria baicalensis , Prunella vulgaris and LL-37, respectively. Elastase secretion was measured using Congo red-elastic proteinase assays. And the expressions of QS genes ( lasI , rhlR ) were analysed by real-time PCR. Results. Single or combined treatments of Scutellaria baicalensis and LL-37 and Prunella vulgaris and LL-37 would significantly reduce elastase secretion. There were no significant differences in proliferation between the groups at any timepoint. All treatments downregulated lasI and rhlR gene expressions. Conclusion. Scutellaria baicalensis , Prunella vulgaris and antimicrobial peptide LL-37 all down-regulate the QS system-related genes of P. aeruginosa , inhibiting the secretion of virulence factors and reducing bacterial toxicity.
Su et al. (Wed,) studied this question.