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<p>Vancomycin-resistant enterococci (VRE), including <i>Enterococcus faecalis</i> and <i>Enterococcus faecium</i>, are multidrug-resistant pathogens with limited treatment options. This study evaluated honey-biosynthesized silver nanoparticles (AgNPs) against VRE using integrated antibacterial, antibiofilm, mechanistic, and preliminary safety assessments. Methods: AgNPs were synthesized using natural honey as a reducing and capping agent and characterized by UV-visible spectroscopy, dynamic light scattering, zeta potential analysis, SEM-EDS, FTIR, and stability assays. Antibacterial activity was assessed using MIC, MBC, agar well diffusion, and time-kill assays. Antibiofilm activity was evaluated by crystal violet assay. Mechanistic responses were examined by molecular docking, RT-qPCR analysis of <i>pbp5</i> and <i>srtA</i>, PBP5 Bocillin-FL binding, and Sortase A activity assays. Preliminary safety was assessed using HEK293 and HepG2 cell viability, LDH release, and erythrocyte hemolysis assays. Results: AgNPs showed MICs of 16&#xa0;µg/mL against <i>E. faecalis</i> and 32&#xa0;µg/mL against <i>E. faecium</i>, with MBCs of 32–64&#xa0;µg/mL and inhibition zones of 14–18&#xa0;mm. Time-kill assays showed &gt; 5 log10 CFU/mL reduction for <i>E. faecalis</i> and approximately 4 log10 CFU/mL reduction for <i>E. faecium</i> after 24&#xa0;h. AgNPs had a hydrodynamic diameter of 18 ± 3&#xa0;nm, PDI of 0.24 ± 0.03, and zeta potential of -32.5 ± 2.1 mV. Biofilm inhibition ranged from 61.4 to 86.5%. AgNP exposure downregulated <i>pbp5</i> and <i>srtA</i>, reduced PBP5 labelling, and decreased Sortase A activity. Cell viability remained ≥ 81%, and hemolysis was &lt; 3%. Conclusion: Honey-biosynthesized AgNPs demonstrated bactericidal and antibiofilm activity against VRE with mechanism-linked effects and acceptable preliminary in vitro tolerance at antibacterial concentration ranges.</p>

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Honey-biosynthesized silver nanoparticles against vancomycin-resistant enterococci: integrated antibacterial, antibiofilm, mechanistic and preliminary safety evaluation

  • 期刊论文

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  • 发表日期：

    2026年7月12日

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  • Ghadah S. Abusalim,
  • Mohammed Alissa

摘要

Vancomycin-resistant enterococci (VRE), including Enterococcus faecalis and Enterococcus faecium, are multidrug-resistant pathogens with limited treatment options. This study evaluated honey-biosynthesized silver nanoparticles (AgNPs) against VRE using integrated antibacterial, antibiofilm, mechanistic, and preliminary safety assessments. Methods: AgNPs were synthesized using natural honey as a reducing and capping agent and characterized by UV-visible spectroscopy, dynamic light scattering, zeta potential analysis, SEM-EDS, FTIR, and stability assays. Antibacterial activity was assessed using MIC, MBC, agar well diffusion, and time-kill assays. Antibiofilm activity was evaluated by crystal violet assay. Mechanistic responses were examined by molecular docking, RT-qPCR analysis of pbp5 and srtA, PBP5 Bocillin-FL binding, and Sortase A activity assays. Preliminary safety was assessed using HEK293 and HepG2 cell viability, LDH release, and erythrocyte hemolysis assays. Results: AgNPs showed MICs of 16 µg/mL against E. faecalis and 32 µg/mL against E. faecium, with MBCs of 32–64 µg/mL and inhibition zones of 14–18 mm. Time-kill assays showed > 5 log10 CFU/mL reduction for E. faecalis and approximately 4 log10 CFU/mL reduction for E. faecium after 24 h. AgNPs had a hydrodynamic diameter of 18 ± 3 nm, PDI of 0.24 ± 0.03, and zeta potential of -32.5 ± 2.1 mV. Biofilm inhibition ranged from 61.4 to 86.5%. AgNP exposure downregulated pbp5 and srtA, reduced PBP5 labelling, and decreased Sortase A activity. Cell viability remained ≥ 81%, and hemolysis was < 3%. Conclusion: Honey-biosynthesized AgNPs demonstrated bactericidal and antibiofilm activity against VRE with mechanism-linked effects and acceptable preliminary in vitro tolerance at antibacterial concentration ranges.