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Background and Aim <p>The increasing prevalence of multidrug-resistant (MDR) <i>Escherichia coli</i>, including strains with reduced susceptibility to last-resort antibiotics such as colistin, represents a major global health concern. Nanoparticle-based delivery systems have been proposed to enhance antimicrobial efficacy. This study aimed to evaluate the antibacterial, antibiofilm, and virulence-modulating effects of colistin-loaded nanoparticles (CS-NPs) in comparison with free colistin () against clinical <i>E. coli</i> isolates.</p> Methods <p>CS-NPs were synthesized using the nanoprecipitation technique and characterized for particle size and polydispersity index and morphology. Antibacterial activity was assessed by determining minimum inhibitory concentrations (MICs) using broth microdilution. Biofilm formation and inhibition were quantified using crystal violet staining. The relative expression of key virulence-associated genes (<i>luxR</i>,<i> luxS</i>,<i> mqsR</i>,<i> fliA</i>,<i> motA</i>,<i> fimH</i>,<i> gapA</i>,<i> and flhD</i>) was analyzed by quantitative real-time PCR. Statistical comparisons were performed using appropriate parametric tests between treatment groups.</p> Results <p>CS-NPs exhibited significantly lower MIC values (0.0625–0.25&#xa0;µg/mL) compared to free CS (0.5–2.0&#xa0;µg/mL, <i>p</i> = 0.012). Biofilm formation was substantially inhibited by CS-NPs at both tested concentrations, with reductions of 63.8% and 56.7%, whereas free CS showed minimal inhibition (12.8% and 3.7%). Furthermore, CS-NPs treatments significantly downregulated all tested virulence-related genes, with higher suppression compared to equivalent doses of free CS. In contrast, low-dose free CS (0.25&#xa0;µg/mL) showed minimal effect on gene expression.</p> Conclusion <p>CS-NPs showed significantly improved in vitro antibacterial and antibiofilm activities, and modulated the virulence-associated gene expression in clinical <i>E. coli</i> isolates. These findings support the further development of nano-formulated colistin as a potential strategy to combat MDR <i>E. coli</i>, highlighting its promise for future in vivo studies and clinical applications.</p>

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Colistin-Loaded PLGA Nanoparticles Enhance the Antibacterial and Antibiofilm Activity and Modulate Virulence Gene Expression in Escherichia Coli

  • 期刊论文

  • 发表日期：

    2026年6月15日

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  • Mahitab S. Abdelaleem,
  • Helal F. Hetta,
  • Noura H. Abd Ellah,
  • Doaa S. Mohamed,
  • Mohamed A. El-Mokhtar

摘要

Background and Aim

The increasing prevalence of multidrug-resistant (MDR) Escherichia coli, including strains with reduced susceptibility to last-resort antibiotics such as colistin, represents a major global health concern. Nanoparticle-based delivery systems have been proposed to enhance antimicrobial efficacy. This study aimed to evaluate the antibacterial, antibiofilm, and virulence-modulating effects of colistin-loaded nanoparticles (CS-NPs) in comparison with free colistin () against clinical E. coli isolates.

Methods

CS-NPs were synthesized using the nanoprecipitation technique and characterized for particle size and polydispersity index and morphology. Antibacterial activity was assessed by determining minimum inhibitory concentrations (MICs) using broth microdilution. Biofilm formation and inhibition were quantified using crystal violet staining. The relative expression of key virulence-associated genes (luxR, luxS, mqsR, fliA, motA, fimH, gapA, and flhD) was analyzed by quantitative real-time PCR. Statistical comparisons were performed using appropriate parametric tests between treatment groups.

Results

CS-NPs exhibited significantly lower MIC values (0.0625–0.25 µg/mL) compared to free CS (0.5–2.0 µg/mL, p = 0.012). Biofilm formation was substantially inhibited by CS-NPs at both tested concentrations, with reductions of 63.8% and 56.7%, whereas free CS showed minimal inhibition (12.8% and 3.7%). Furthermore, CS-NPs treatments significantly downregulated all tested virulence-related genes, with higher suppression compared to equivalent doses of free CS. In contrast, low-dose free CS (0.25 µg/mL) showed minimal effect on gene expression.

Conclusion

CS-NPs showed significantly improved in vitro antibacterial and antibiofilm activities, and modulated the virulence-associated gene expression in clinical E. coli isolates. These findings support the further development of nano-formulated colistin as a potential strategy to combat MDR E. coli, highlighting its promise for future in vivo studies and clinical applications.