Green Synthesis of Silver Nanoparticles: Antimicrobial Efficacy against MDR Clinical Isolates and In Vitro Cytotoxicity Assessment

Abstract

The environmental crises and rising multidrug -resistant (MDR) infections demand sustainable antimicrobial solutions. This study biosynthesized silver nanoparticles using Lactobacillus plantarum cell -free supernatant, characterized their   physicochemical properties, and evaluated antimicrobial, antibiofilm, synergistic, and  cytotoxic  activityes  against  MDR  clinical  isolates  from  Iraq    . AgNPs were synthesized    via AgNO3   reduction and characterized using  UV-Vis, FTIR,XRD, TEM, SEM, and    zeta  potential. Fifty isolates— including   Escherichia coli ,  Klebsiella  pneumoniae , Staphylococcus aureus,  Pseudomonas  aeruginosa,  shigella spp., and NDM-1- positive strains— were  obtained  from   Thi Qar,  Iraq. UV-Vis confirmed bio reduction   at 420 nm; XRD revealed 18 nm crystallite   size; TEM/SEM showed   uniform spherical morphology and zeta  potential  indicated  colloidal  stability. AgNPs exhibited potent bactericidal / bacteriostatic activity and 62-89% biofilm inhibition at sub- MIC concentrations.  Synergistic effects with ampicillin and   ciprofloxacin were confirmed  via  checkerboard  assay.  MTT assay demonstrated selective toxicity against  human  dermal  fibroblasts. Biogenic AgNPs represent promising biocompatible alternatives for combating MDR infection, combining potent antimicrobial efficacy, antibiofilm activity, antibiotic synergy, and favorable safety profiles for clinical translation.