Synergistic Effect of Silver Nanoparticles and Streptomycin Antibiotic on the MexX Gene Expression of Pump Efflux System in Drug-Resistant Pseudomonas aeruginosa Strains

Introduction: Pseudomonas aeruginosa is one of the most important infectious agents in humans, which is difficult to control in hospitals due to its resistance to various antibiotics. Efflux pump systems play an important role in the drug resistance of this bacterium to a variety of antibiotics. This study aimed to determine the antimicrobial synergistic effect of silver nanoparticles and the antibiotic streptomycin on the MexX gene expression. Material & Methods: In this cross-sectional descriptive study, 49 samples were collected from 11 medical diagnostic laboratories in Mashhad from 1398 to 1399. After the treatment of multidrug-resistant bacteria with inhibitors, the microdilution method and Real Time-PCR technique were used to determine the effective dilution of silver nanoparticles and probiotics on the expression of the MexX gene of the bacterium. (Ethic code: IR.IAU.MSHD.REC.1400.018) Findings: All 49 collected samples of Pseudomonas aeruginosa were identified. All strains had the MexX gene, and all were resistant to more than two antibiotics. The minimum inhibitory concentration (MIC) results and expression of the MexX gene showed that the MIC in the agar dilution method for silver nanoparticles was up to 500 μg/ml. Evaluation of the synergistic effect of silver nanoparticles with streptomycin antibiotic showed that plates containing streptomycin antibiotic disk with silver nanoparticles with the dilution of 250 μg/ml caused a growth inhibition zone according to the CLSI standard. Silver nanoparticles with streptomycin synergy had a greater effect in inhibiting bacterial growth, and this effect was greater than that of silver nanoparticles (P>0.05). Discussion & Conclusion: Silver and streptomycin have inhibitory and antibacterial activity to reduce the function of the MexXY-OprM efflux pump in Pseudomonas aeruginosa (P>0.05).