Regulation of virulence factors ofby,and antimicrobial peptide LL-37.

The increasing resistance and the pathogen's complex multi-drug resistance mechanisms made the selection of effective antimicrobial treatments more challenging for(). The study aimed to explore the effect of,and antimicrobial peptide LL-37 on the virulence factors of.Previous studies have shown that extracts from traditional Chinese medicines,and, can also enhance the effects of antibiotics and reduce antibiotic resistance in. 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,and LL-37 inremains unknown.We explored whether the combined use of,and LL-37 can exert antibacterial effects through the quorum sensing (QS) system.The minimal inhibitory concentrations of,and LL-37 were determined forandusing micro broth dilution. The antibacterial activity ofcombined with LL-37 andcombined with LL-37 was also assessed. The growth abilities ofwere analysed after being treated with,and LL-37, respectively. Elastase secretion was measured using Congo red-elastic proteinase assays. And the expressions of QS genes (,) were analysed by real-time PCR.Single or combined treatments ofand LL-37 andand LL-37 would significantly reduce elastase secretion. There were no significant differences in proliferation between the groups at any timepoint. All treatments downregulatedandgene expressions.,and antimicrobial peptide LL-37 all down-regulate the QS system-related genes of, inhibiting the secretion of virulence factors and reducing bacterial toxicity.