Antibacterial and antibiofilm synergy of silver-selenium core-shell nanoparticles with meropenem against multidrug-resistant Klebsiella pneumoniae isolated from catheter-related urinary tract infections

Abstract

Objective: To evaluate the antibacterial and antibiofilm efficacy of cold plasma‑synthesised silver‑selenium (Ag@Se) core–shell nanoparticles, alone and in combination with meropenem, against multidrug‑resistant Klebsiella pneumoniae isolates from catheter‑associated urinary tract infections.

Methods: Ag@Se nanoparticles were synthesised using an atmospheric cold plasma jet system. Characterisation was performed by UV‑Vis spectroscopy, X‑ray diffraction (XRD) and transmission electron microscopy (TEM). Cytotoxicity was assessed on rat embryo fibroblast (REF) cells. Among 200 urine samples, 67 K. pneumoniae isolates were identified; 30 were multidrug‑resistant, and five highly resistant isolates with strong biofilm formation were selected for synergy testing using checkerboard assays. Biofilm formation was quantified by crystal violet microtiter plate method.

Results: XRD confirmed a face‑centred cubic silver core; TEM showed core–shell structures of ~100 nm. Ag@Se nanoparticles exhibited low cytotoxicity (maximum growth inhibition 23.3 % at 48 h, 100 µg/mL). Against the five selected isolates, Ag@Se alone achieved 50–65 % growth inhibition. Combination with meropenem increased inhibition to 60–70 %. Synergy was confirmed by isobologram and combination index analyses.

Conclusion: Plasma‑synthesised Ag@Se nanoparticles enhance meropenem activity against MDR K. pneumoniae and show acceptable biocompatibility, offering a promising nano‑antibiotic strategy for biofilm‑associated urinary tract infections.