Antibacterial and antibiofilm evaluation of biogenic ternary CuO–AgO–MgO nanocomposite against clinical isolates of carbapenem-resistant <i>Klebsiella pneumoniae</i>

Escalation of antimicrobial resistance amongst Klebsiella pneumoniae (K. pneumoniae) represents a remarkable worldwide health concern. This study reports the green biosynthesis of copper, silver and magnesium oxide trimetallic nanocomposites (CuO–AgO–MgO TNCs) using banana peel extract as a safe and sustainable reducing and stabilizing agent and emphasizes its inhibitory activity against carbapenem-resistant K. pneumoniae (CRKP) strains. The TNCs were characterized by ultraviolet–visible (UV–vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis, confirming their crystalline structure (average size 125 nm) and elemental composition (Cu, Ag, Mg, O). Cytotoxicity assessment using WI-38 normal cells showed minimal toxic effect with an IC50 of 193.49 ± 2.85 µg/mL. Antibacterial activity was evaluated against genotypically diverse CRKP strains. Well diffusion assay (WDA) showed inhibition zones of 18–38 mm, while the broth microdilution assay provided minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranging from 8 to 1024 µg/mL and 128 to 2048 µg/mL, respectively. Time-kill assays indicated rapid bacterial growth reduction within 2 h, and antibiofilm assays showed 25–91% inhibition of biofilm formation. The image provided by SEM revealed pronounced morphological alterations in treated bacterial cells. Our findings exhibited biogenic CuO–AgO–MgO TNCs with potent antibacterial and antibiofilm activities against CRKP while showing negligible toxicity towards normal cells, highlighting their potential as a safe and effective alternative antimicrobial strategy.