Antibacterial efficacy of Nonea lutea-mediated silver and gold nanoparticles against multidrug-resistant clinical pathogens harboring virulence and resistance genes.

Abstract

Introduction: The emergence of high-level antibiotic-resistant bacteria, such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus, represents a critical global health threat that requires novel therapeutic strategies. The use of Green-synthesized gold and silver nanoparticles is a suitable solution, and Nonea lutea plant, due to its promising phytochemical properties and traditional medicinal uses, can be used for this purpose. This study aimed to investigate the antimicrobial effect of these nanoparticles on multidrug-resistant (MDR) isolates carrying multiple virulence and resistance genes.

Materials and methods: One-hundred clinical isolates of each organism were collected and identified. Antibiotic resistance pattern of them was investigated by disk agar diffusion method. Bacterial DNA was extracted by alkaline lysis method and the presence of virulence and antibiotic resistance genes was assessed using PCR. Then, 15 MDR isolates of each organism containing multiple virulence genes were selected. Green-synthesized silver and gold nanoparticles from methanolic extract of N. lutea were prepared and their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated against the isolates.

Results: All 15 MDR P. aeruginosa isolates harbored the exoU, exoA, bla_CTX-M, bla_TEM and bla_OXA-2 genes, while the bap and csuE genes in A. baumannii and the icaA gene in S. aureus had a 100% frequency. The MICs of N. lutea Green-synthesized silver nanoparticles against P. aeruginosa, A. baumannii, and S. aureus isolates were 0.19-1.56 µg/mL, 0.19-0.78 µg/mL, and 0.19-0.39 µg/mL, respectively. Meanwhile, the MBCs of Green-synthesized silver nanoparticles against these isolates were 0.19-1.56 µg/mL, 0.39-0.78 µg/mL, and 0.39-12.5 µg/mL, respectively. While the MICs of Green-synthesized gold nanoparticles was weaker and the chemically synthesized nanoparticles showed limited antimicrobial activity (MIC > 500 µg/mL) under the tested conditions.

Conclusion: Green-synthesized silver nanoparticles demonstrated promising in vitro antibacterial activity against MDR isolates. However, further mechanistic and in vivo studies are required to fully assess their therapeutic potential.