Antibacterial and antibiofilm effects of α-humulene against .

The rapid increase in antibiotic resistance has prompted the discovery of drugs that reduce antibiotic resistance or new drugs that are an alternative to antibiotics. Plant extracts have health benefits and may also exhibit antibacterial and antibiofilm activities against pathogens. This study determined the antibacterial and antibiofilm effects of α-humulene extracted from plants against enterotoxigenic , which causes inflammatory bowel disease. The minimum inhibitory concentration and biofilm inhibitory concentration of α-humulene for were 2 μg/mL, and the biofilm eradication concentration was in the range of 8-32 μg/mL. The XTT reduction assay confirmed that the cellular metabolic activity in biofilm rarely occurred at the concentration of 8-16 μg/mL. In addition, biofilm inhibition by α-humulene was also detected via confocal laser scanning microcopy. Quantitative real-time polymerase chain reaction (qPCR) was also used to investigate the effect of α-humulene on the expression of resistance-nodulation-cell division type multidrug efflux pump genes ( and ). According to the results of qPCR, α-humulene significantly reduced the expression of and genes. This study demonstrates the potential therapeutic application of α-humulene for inhibiting the growth of cells and biofilms, and it expands the knowledge about biofilm medicine.