Synthesis of Biogenic Silver Nanoparticles with Aqueous Extract of Azadirachta indica Seed and Its Antimicrobial Activity on MDR and ESBL-Producing Escherichia coli.

The emergence of multidrug-resistant (MDR) and extended-spectrum {beta}-lactamase (ESBL)-producing Escherichia coli poses a significant threat to global public health, necessitating the development of alternative antimicrobial strategies. In this study, biogenic silver nanoparticles (AgNPs) were synthesized using aqueous seed extract of Azadirachta indica as a green, eco-friendly reducing and stabilizing agent. Successful synthesis of nanoparticles was confirmed by a visible color change and characterized using UV-Visible spectroscopy, FTIR, XRD, DLS, SEM, EDAX, and TEM analyses. The synthesized AgNPs exhibited a strong surface plasmon resonance peak at 420 nm and were predominantly spherical with an average size of [~]38 nm and a zeta potential of -24.26 mV, indicating moderate stability. The antimicrobial efficacy of the synthesized AgNPs was evaluated against 88 clinical isolates of MDR and ESBL-producing E. coli. The nanoparticles demonstrated potent antibacterial activity with a minimum inhibitory concentration (MIC) ranging from 1.5625 to 3.125 {micro}g/mL and bactericidal effects at low concentrations, significantly outperforming the neem seed extract alone. Cytotoxicity assessment using HEK-293 cell lines revealed a relatively high IC50 value (297.01 {+/-} 10.04 {micro}g/mL), suggesting low toxicity at effective antimicrobial doses. Overall, the study highlights the potential of A. indica seed-mediated AgNPs as an effective and biocompatible antimicrobial agent against resistant bacterial strains, warranting further in vivo investigations for clinical applications.