Potentiating Gentamicin Efficacy Against Biofilms of Clinically Relevant Gram-Negative Bacteria Using Biosynthesized ZnO Nanoparticles

Background: Gram-negative bacteria resistant to multiple drugs are a major cause of illness and death worldwide. Their remarkable capacity to develop resistance to antibiotics makes them a serious concern in medical practice. Methods: A simple, green, novel method is used to synthesize ZnO nanoparticles (ZnO NPs) using ethanolic extracts of Diplazium esculentum via precipitation. Results: ZnO NPs exhibit a hexagonal structure with a particle size of ~30 nm and a band gap of 3.24 eV. The defect sites formed in ZnO NPs were estimated using prominent peaks in the photoluminescence spectra. ZnO NPs displayed a more than 4-log reduction in multi-drug-resistant E. coli and K. pneumoniae clinical isolates at a 500 μg/mL concentration. Moreover, ZnO NPs significantly reduced the biofilm bacterial cell viability of clinical isolates of Gram-negative bacteria. Complete eradication of biofilms was achieved for drug-resistant E. coli clinical isolates using a combination of sub-MIC of gentamicin and 500 μg/mL ZnO NPs. Green-synthesized ZnO NPs did not induce oxidative stress in mice, as indicated by unchanged GST, GSH, and thiol levels across all the tested organs. ZnO NPs showed both antibacterial and antibiofilm efficacy against drug-resistant strains of E. coli, K. pneumoniae, and S. aureus and completely eradicated E. coli biofilm in combination with gentamicin. Conclusions: Our study focuses on the sustainable synthesis of biocompatible ZnO NPs for the treatment of infections caused by pathogens belonging to the high-priority ESKAPE group.