Effect of the chitosan-zinc oxide nanocomposite with gentamicin on expression of genes associated with quorum sensing in Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is an opportunistic, nosocomial pathogen for which antibiotic resistance and biofilm development is common. Quorum sensing (QS) communication is known to be a major controlling factor in virulence gene expression, biofilm development and antibiotic resistance in P. aeruginosa. Therefore, we are interesting for exploring new medications for their antiquorum sensing activity. Methods: In the present study, chitosan-zinc oxide (CS-ZnO) nanocomposite with/without gentamicin was synthesized and was characterized with the DLS (Dynamic Light Scattering), FTIR (Fourier Transform Infrared), XRD (X-ray Diffraction) and SEM (Scanning Electron Microscope). The minimum inhibitory concentrations (MICs) against P. aeruginosa PAO1 determined using broth microdilution methods. The influence of sub-MIC (1/4 MIC) and MIC concentrations of CS-ZnO nanocomposite and gentamicin alone and in combination on sensitivity to H2O2, biofilm formation, pyocyanin production, swarming and twitching motilities was evaluated and was confirmed by RT-PCR to test the expression of the QS regulatory genes lasI and rhlI . Results: A four-fold MIC reduction in P. aeruginosa PAO1 treated by the gentamicin loaded CS-ZnO nanocomposite was observed. At MIC concentrations, the gentamicin-loaded CS-ZnO nanocomposite was significantly inhibited QS-regulated phenotypes and genes such as pyocyanin secretion (82.4%), biofilm formation (84%), swarming (76%) and twitching (73.6%) motilities and expression of lasI (74%) and rhlI (79%) genes, as well as, incereased inhibition growth zone (134%) in comparison with untreated P. aeruginosa PAO1 (P < 0.05).