Molecular insights into the inhibition of MexCD-OprJ efflux pumps by menthol and thymol in Pseudomonas aeruginosa
摘要
MexCD-OprJ is one of the major efflux systems which confers significant drug resistance to Pseudomonas aeruginosa. This study aimed to investigate the effects of two herbal compounds, menthol and thymol, on the MexCD-OprJ efflux pump in P. aeruginosa isolates. Ethidium bromide (EtBr) agar cartwheel, disk diffusion, and antibiogram tests were carried out for the isolates, with and without exposure to sub-MIC values of menthol and thymol. The expression level of the oprJ gene was evaluated through reverse transcription quantitative PCR (RT-qPCR). In order to check the interactions between the OprJ protein and the herbal agents, molecular docking was conducted using Autodock v4.2.6. Cartwheel method demonstrated inhibition of pump activity in all isolates grown under sub-MIC of the bioactive compounds. The untreated bacteria (control group) were resistant to antibiotics; however, the antibiotic sensitivity of the isolates shifted toward sensitive or intermediate patterns in several cases after exposure to menthol and thymol, depending on the specific antibiotics employed. Additionally, thymol and menthol downregulated the expression of the oprJ (P < 0.05). According to the in silico analysis, the herbal compounds may potentially interact with the α-barrel and β-barrel channels considering the amino acids involved in the interactions, with menthol showing greater binding energy (ΔG = -5.81 kcal.mol−1) with the OprJ protein compared to thymol (ΔG = -5.63 kcal.mol−1). Our findings indicate that menthol and thymol may serve as potential inhibitors of the MexCD-OprJ efflux system of P. aeruginosa, offering a promising avenue for antibiotic treatment.