Comparative Evaluation of Pine Seed Oil and Green-Synthesized Silver Nanoparticles on Quorum-Sensing Genes (LuxS and lsrR) in Escherichia coli

Abstract

     Autoinducer-2 (AI-2)–mediated quorum sensing (QS) is a key regulatory mechanism controlling biofilm formation and virulence in Escherichia coli. This study aimed to compare the effects of pine seed oil and green-synthesised silver nanoparticles (AgNPs) on the expression of LuxS and lsrR genes involved in QS regulation. A total of 155 clinical samples were collected from patients in Babylon hospitals, from which 75 E. coli isolates were obtained; 25 were selected for molecular analyses. AgNPs were synthesised using pine seed oil extract and characterised by UV-Vis spectroscopy, FTIR, SEM, AFM, EDX, and XRD. Sub-minimum inhibitory concentrations (sub-MICs) of pine oil (1 mg/ml) and AgNPs (32 µg/ml) were used for gene expression studies by qRT-PCR, using 16S rRNA as a housekeeping gene. The results revealed significant down-regulation of LuxS and lsrR genes in isolates treated with AgNPs compared to pine oil (mean fold-change for LuxS: 0.84 ± 0.05 vs 0.98 ± 0.07; for lsrR: 0.57±0.03 vs 0.89 ± 0.04; p≤0.05). The findings indicate that green-synthesised AgNPs more effectively suppress QS gene expression in E. coli than pine seed oil, suggesting their potential as alternative anti-virulence agents, pending further in vivo and toxicity studies.