Green Synthesis of Silver Nanoparticles Using Moringa oleifera and Its Synergistic Antibacterial Activity against mecA Gene‐Carrying Bacteria

The rising incidence of methicillin-resistant Staphylococcus aureus (MRSA), especially mecA-positive strains, demands alternative antibacterial strategies. Although Moringa oleifera-mediated silver nanoparticles (AgNPs) have been reported previously, their activity against genetically confirmed mecA-positive MRSA and their interaction with vancomycin remain insufficiently documented. M. oleifera leaf aqueous extract was used as a reducing and capping agent for green synthesis of AgNPs from 1 mM AgNO₃. Nanoparticle formation was monitored by visual color change and Ultraviolet-visible (UV-vis) Spectroscopy (300-700 nm; lambda max 430 nm), while Fourier Transform Infrared (FTIR), transmission electron microscopy (TEM), and x-ray diffraction (XRD) were used for structural characterization. Antibacterial activity was assessed by agar well diffusion and broth microdilution against mecA-positive MRSA isolates, and cytotoxicity was evaluated on human dermal fibroblast (HDF) and epithelial cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Brown colloids formed within 30 min and showed a distinct surface plasmon resonance (SPR) band at 430 nm. TEM revealed predominantly spherical particles with sizes of 10-28 nm (mean 15.8 +/- 3.0 nm), while XRD confirmed crystalline face-centered cubic silver. The biosynthesized AgNPs produced inhibition zones of 19.1 +/- 0.7 to 23.0 +/- 0.9 mm, compared with 8.3 +/- 0.5 to 12.0 +/- 0.6 mm for the crude extract, and reduced the MIC from 96 +/- 5.4 ug/mL for the extract to 12 +/- 2.1 ug/mL. The AgNP-vancomycin combination further reduced the mean MIC to 4 +/- 0.9 ug/mL and increased the inhibition zone to 26.4 +/- 1.1 mm. HDF cell viability remained >79% at 100 ug/mL for AgNPs and >72% at 100 ug/mL for Epithelial cells. M. oleifera-mediated AgNPs showed stronger anti-MRSA activity than the parent extract and enhanced vancomycin activity in vitro.