Harnessing silica-coated silver nanoparticles for combating multidrug-resistant Pseudomonas aeruginosa

Multidrug-resistant (MDR) Pseudomonas aeruginosa poses a critical challenge in clinical settings because of its resistance to conventional antibiotics. This study investigated the antibacterial potential of silica-coated silver nanoparticles (SiO₂@AgNPs) against MDR P. aeruginosa and explored their synergistic interactions with selected antibiotics. A total of 450 pus samples were processed for bacterial isolation, and P. aeruginosa was identified using standard microbiological methods. MDR strains were confirmed using MIC-based VITEK antimicrobial susceptibility testing and RT-PCR for resistance genes. The antibacterial activity of the SiO₂@AgNPs was assessed using the microbroth dilution method. A checkerboard assay was conducted against MDR isolates to determine the synergy between SiO₂@AgNPs and ciprofloxacin, meropenem, and ceftazidime-avibactam. The synthesized nanoparticles were characterized using transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analysis. Of the 450 pus samples, 100 P. aeruginosa isolates were identified, of which 13 were classified as MDR P. aeruginosa. SiO₂@AgNPs exhibited effective antibacterial activity, with an MIC of 500 µg/mL against MDR P. aeruginosa. Checkerboard assays demonstrated strong synergy with meropenem and ceftazidime-avibactam (FICI = 0.375) and partial synergy with ciprofloxacin (FICI = 0.625-1.0625). TEM revealed spherical particles with an average size of 10 nm, FTIR confirmed SiO₂ functional groups, and XRD revealed crystalline silver nanoparticles within an amorphous silica matrix. These findings indicate that SiO₂@AgNPs possess potent antibacterial activity against MDR P. aeruginosa and can enhance the efficacy of certain antibiotics, highlighting their potential in combination therapy against resistant strains. KEY POINTS: ● Silica-coated silver nanoparticles effectively inhibited MDR P. aeruginosa. ● SiO₂@AgNPs enhance the efficacy of meropenem and ceftazidime-avibactam. ● Nanoparticle-antibiotic combinations may offer new strategies for treating resistant infections.