Menthol and thymol reduce the expression level of the OprJ gene in Pseudomonas aeruginosa

BACKGROUND AND OBJECTIVESAntibiotic efflux is one of the most important mechanisms of bacterial resistance to antibiotics. Studies have shown that various plant-derived compounds are able to deactivate efflux activity. Here, the effect of menthol and thymol as bioactive compounds on the expression of the MexCD-OprJ efflux pump encoding gene in different isolates of Pseudomonas aeruginosa was assessed through molecular methods.MATERIALS AND METHODSThe genomic DNAs of bacterial isolates were extracted using a DNA Extraction Kit (SinaClon, Iran) to screen them for the presence of the OprJ gene. To analyze the expression of the pump gene, real-time PCR (for the ones exposed to bioactive compounds, and controls without bioactive compounds) was carried out. Bacterial isolates of P. aeruginosa were cultured in broth media under sub-MIC values of menthol and thymol. The controls were prepared without exposure to bioactive compounds. The total RNAs of the overnight cultures were extracted using an RNA Extraction Kit (SinaClon, Iran). The cDNAs were synthesized from mRNAs using a cDNA Synthesis Kit (SinaClon, Iran), and then real-time PCR was conducted according to the manufacturer’s protocol. Data were analyzed by student’s t-test using GraphPad Prism ۸.RESULTS AND DISCUSSIONThe results of the real-time PCR revealed that both bioactive compounds managed to significantly decrease (p < ۰.۰۵) the expression of the OprJ gene.CONCLUSIONGiven the molecular evidence provided in the current research, menthol and thymol can serve as inhibitory candidates of P. aeruginosa’s MexCD-OprJ efflux pump to pave the path for antibiotic treatment.

کلیدواژه ها:

Efflux pump ، Menthol ، MexCD-OprJ ، OprJ gene ، Pseudomonas aeruginosa ، Thymol