Evaluation of Chitosan and Zinc Oxide Nanoparticles Inhibitory Effects on Expression Levels of Virulence Genes at Pseudomonas aeruginosa Clinical Isolates and ATCC27853

 Quorum sensing (QS) and virulence genes in Pseudomonas aeruginosa causing severe infections in humans. In the present study, the effect of chitosan (CS) and zinc oxide nanoparticles (ZnO-NPs) on the expression level of lasI, exoS and toxA genes during lag, exponential-and stationary growth phases of P. aeruginosa were studied.

 CS and ZnO-NPs were synthesized by ionic gelation and ultrasonic methods, respectively. The clinical samples were collected from patients suffering from wound infections from 2018-2019, and preliminary identification of P. aeruginosa has done with the standard biochemical tests and 16S rDNA gene. The virulence genes (lasI, exoS and toxA) were detected by polymerase chain reaction (PCR). Finally, real-time reverse transcription-PCR (qRT-PCR) was performed to detect the expression level of QS and virulence-related genes in samples grown at a medium contain minimum inhibitory concentrations (MICs) of CS and ZnO-NPs.

 CS and ZnO-NPs were successfully prepared with average particle sizes of 20 and 40 nm. The prevalence rate of virulence-related genes among all clinical isolates originated from burn patients was as follows; toxA (100%), exoS (88%), and lasI (56%). The MIC value of CS was equal to 0.5 mg/mL, which is 8-fold lower than that for ZnO-NPs (4 mg/mL). qRT-PCR analysis revealed CS and ZnO-NPs decrease the expression of lasI, exoS, and toxA in clinical P. aeruginosa isolates during the exponential phase compared to other growth phases. toxA+/exoS+/lasI+ isolates exhibited similar patterns of gene expression changes in response to both NPs at all growth phases. Expression of toxA gene downregulated at exponential-and stationary growth phases of ATCC27853 treated with CS and ZnO-NPs.

 The results obtained from this study may provide a better understanding of the expression changes of virulence-related genes throughout different growth phases of P. aeruginosa.