Zinc oxide nanoparticles are promising antibacterial agents, owing to their unique physicochemical properties and broad-spectrum antibacterial activity. A study was conducted to evaluate the antibacterial efficacy of ZnO NPs against clinical isolates of P. aeruginosa. In addition, the impact of ZnO NPs on the expression of genes pelA and lasI, the effect of ZnO NPs and ciprofloxacin on the expression of pelA and lasI genes using quantitative real-time PCR. A total 207 clinical and environmental specimens, including burn swabs, urine, wound swabs, sputum, ear swabs, endotracheal tube aspirates, bronchial washings, and operation room samples, were screened for P. aeruginosa. The isolates were identified and confirmed using the VITEK 2 System. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method. Gene pelA and gene lasI were detected by PCR.The antibacterial activities of ZnO-NPs, and ciprofloxacin was measured, RNA was extracted from treated bacterial, followed by cDNA synthesis to determine the effects of ZnO-NPs and ciprofloxacin on gene expression. The cytotoxicity of ZnO-NPs was assessed using the MTT assay. From all specimens, 47 P. aeruginosa isolates were identified, and 20 of these isolates exhibited multidrug resistant. Molecular analysis revealed that all MDR isolates possessed both the pelA, and lasI genes. Isolates P10 and P16 were selected for further analysis because they exhibited strong biofilm formation and possessed both genes. MIC of the ZnO-NPs against P. aeruginosa was 1300 µg/ml. Treatment with sub-MIC of ZnO and sub-MIC of ciprofloxacin significantly reduced the expression of pelA and lasI genes, with relative expression levels of 0.163 - 0.534, respectively (P< 0.05). Furthermore, the combination of ZnO-NPs and ciprofloxacin demonstrated a synergistic effect, resulting in greater suppression of biofilm-related gene expression. These findings suggest for that ZnO-NPs, combination with ciprofloxacin, may represent a promising strategy for controlling MDR P. aeruginosa and inhibiting biofilm formation.
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