Evaluation of Gold Nanoparticles on the Expression of NorA and NorB Efflux Pumps in Ciprofloxacin-resistant Staphylococcus aureus Isolated from Burn Patients

Abstract

Background: In the development of multidrug resistance, efflux pumps effectively pump drug compounds out of cells, which results in reduced membrane permeability to drug compounds. This study evaluated the effect of gold nanoparticles on the inhibition of norA and norB efflux pumps in ciprofloxacin-resistant Staphylococcus aureus isolated from burn patients in Qom province, Iran. Methods: In this cross-sectional study, S. aureus strains were isolated from burn patients in Qom hospital, Iran. After gold nanoparticles were synthesized using chemical reduction and characterized by spectrophotometry, transmission electron microscopy (TEM), and dynamic light scattering (DLS), ciprofloxacin resistance of S. aureus was screened by the disc diffusion method. The Minimum Inhibitory Concentration (MIC) of ciprofloxacin (CCCP), ciprofloxacin + gold nanoparticles (CCCP + gold nanoparticles), and ciprofloxacin + CCCP was determined. Moreover, norA and norB genes were evaluated by PCR using special primers. Real-time PCR was then performed for norA and norB genes. Results: Of 88 S. aureus strains tested, 50 (56.81%) were resistant to ciprofloxacin. From the 50 ciprofloxacin-resistant S. aureus strains, 12 isolates had active pumps. Real-time PCR of 12 ciprofloxacin- resistant S. aureus and S. aureus ATCC 25923 before and after exposure to ciprofloxacin, gold nanoparticles, and gold nanoparticles with sub-MIC ciprofloxacin revealed significant differences in expression of norA and norB genes before exposure to the treatments compared to after exposure (p <0.05). Conclusion: Gold nanoparticles with ciprofloxacin could be used to prevent the expression of pump genes involved in resistance to fluoroquinolone compounds.