Allium cepa mediated green synthesis of ZnO nanoparticles with antibacterial antibiofilm and synergistic activity against uropathogenic multidrug resistant Escherichia coli

This study evaluates Allium cepa-mediated zinc oxide (ZnO) nanoparticles (NPs) as a novel therapeutic approach. The Green-synthesized ZnO NPs, characterized by UV-Vis spectroscopy, FTIR, XRD, and SEM, revealed a crystalline hexagonal structure with an average particle size of 32.20 nm. Among 10 uropathogenic E.coli isolates, confirmed by PCR targeting uspA gene, showed biofilm formation in the crystal violet assay. ZnO NPs proved to be potent antibacterial agent with mean ZOI ranged from 20.00 ± 0.40–22.00 ± 1.00 mm in disc diffusion assay and minimum inhibitory concentrations (MICs) were from 11.45 ± 11.8 to 18. 74 ± 10.82 µg/mL in microbroth dilution method. ZnO NPs showed better antibiofilm activity as indicated by minimum biofilm inhibitory concentrations (MBICs) (625.00 ± 0.00–1041.67 ± 360.84 µg/mL) in microbroth dilution coupled with crystal violet assay. Synergism was observed through disc diffusion assay and the crystal violet assay. In the disc diffusion method, synergy was observed for ZnO NPs combination with ceftriaxone (CRO) and gentamicin (CN) against E. coli 5 and CN and meropenem (MEM) against E. coli 7. In crystal violet assay, synergism was observes by sulphamethoxazol trimethprim SXT (FICI; 0.07) against E.coli 4, by gentamicin (CN) against E.coli 5 (FICI; 0.49) and E.coli 7 (FICI; 0.41). The synergistic effects of antibiotics suggest that Allium cepa-mediated ZnO NPs are promising alternatives for combating MDR E.coli in UTIs, potentially revolutionizing therapeutic strategies.