The effect of silybin-encapsulated micelle nanoparticles on mexY expression in ciprofloxacin-resistant isolates of Pseudomonas aeruginosa

  Pseudomonas aeruginosa is a major nosocomial infection in immunocompromised patients. Silybin as an herbal drug has anti-inflammatory and anti-cancer effects and recently further studies have been focused on its antibacterial functions. The aim of this study was to investigate the antibacterial effect of silybin on mexY gene expression in ciprofloxacin (CP)-resistant isolates of P. aeruginosa. In this study, six ciprofloxacin- resistant isolates of P. aeruginosa were both treated by ciprofloxacin (1/2 MIC) only as a control sample and in combination with silybin-encapsulated micelles (nanoparticles) as the test sample. MBC test was performed 24 h after culturein Mueller-Hinton agar. After RNA extraction and cDNA synthesis, mexY expression was quantitatively investigated in silybin- treated and untreated cells. Our findings showed that a combined silybin-encapsulated micelles and ciprofloxacin (1/2 MIC) treatment reduces the bacterial growth up to 50% after 24h. Also Q-RT-PCR analysis revealed that silybin-encapsulated micelles decrease mexY expression. Our results suggest that silybin could inhibit bacterial growth by decreasing mexXY-oprM efflux pump count on the cell surface.