Deregulation of Mexb Gene in Ciprofloxacin Resistant Isolates of Pseudomonas Aeruginosa Treated with Silibinin-Encapsulated in Nanoparticles

Silibinin (silybin) is an active component of silymarin with anti-bacterial activities. In drug resistant isolates of Pseudomonas aeruginosa has been reported overexpression of mexB gene. The aim of this study was evaluation of mexB gene expression in silibinin treated and untreated isolates of Pseudomonas aeruginosa.
In this descriptive analytical study, Pseudomonas aeruginosa isolates were obtained from hospitals and laboratories of Guilan province. After determining several antibiotics susceptibility (disc diffusion and MIC), 5 ciprofloxacin resistant isolates of Pseudomonas aeruginosa were treated by ciprofloxacin (1/2MIC) only (group1) and in the combination with silibinin-encapsulated micelles (nanoparticles) (group2). After 24h, RNA extraction and cDNA synthesis was performed in group1 and group2 and mexB gene expression was evaluated by quantitative-realtime PCR (Q-RT-PCR) and 2-ΔΔCT equation.
FINDINGS: In this study from 69 isolates, 33.33% by disc diffusion test and 37.86% by MIC test were determined ciprofloxacin resistant. Our analysis showed that silibinin -encapsulated nanoparticles (400µg/ml) induced death up t0 50% in ciprofloxacin (1/2MIC) treated resistant isolates during 24h. In treated cells with silibinin and ciprofloxacin revealed downregulation of mexB gene compared to treated cells with ciprofloxacin alone.
It seems that silibinin is cause of increasing ciprofloxacin effect on inhibition of growth of Pseudomonas aeruginosa through decreasing expression of genes implicated in efflux pomp systems such as mexB.