Chitosan and chitosan-zinc oxide nanocomposite inhibit expression of LasI and RhlI genes and quorum sensing dependent virulence factors of Pseudomonas aeruginosa.

The great ability of Pseudomonas aeruginosa to cause chronic infection is attributed to several virulence factors, biofilm formation, intrinsic and acquired resistance to many antibiotics. Anti-quorum sensing (QS) and anti-virulence therapy are promising alternatives to the existing antibiotic therapy. In this study, the effect of chitosan and the prepared chitosan-zinc oxide (CH/ZnO) nanocomposite on QS-dependent virulence factors and acyl homoserine lactone "AHL" production was studied. The chemical structure of the prepared CH/ZnO nanocomposite was characterized by FT-IR spectrum and XRD. The thermal stability and particle size were determined. Chitosan causes a significant decrease in AHL, biofilm, pyocyanin production and motility of P. aeruginosa. CH/ZnO nanocomposite augments the inhibitory activity of chitosan in both phenotypic and genotypic levels. Both chitosan and CH/ZnO nanocomposite downregulate the expression of LasI and RhlI genes using quantitative real-time PCR. The expression of RhlI gene in PAO1 is reduced by 1240 folds after treatment with CH/ZnO nanocomposite. The expression of LasI and RhlI genes in clinical isolates is reduced by 1778.07 and 627.29 folds upon treatment with CH/ZnO. These promising results may find a rescue in the battle of fighting P. aeruginosa by repressing its QS-dependent virulence factors.