Effects of iron oxide (Fe₃ O₄ ) nanoparticles on Escherichia coli antibiotic-resistant strains

Antibiotic resistance of different bacteria requires the development of alternative approaches for overcoming this phenomenon. The antibacterial effects of iron oxide (Fe₃ O₄ ) nanoparticles (NPs) (from 50 to 250 μg ml^-1 ) on Escherichia coli antibiotic-resistant strains have been aimed.

The study was performed with ampicillin-resistant E. coli DH5α-pUC18 and kanamycin-resistant E. coli pARG-25 stains. Specific growth rate of bacteria (μ), lag phase duration and colony-forming units (CFU) were determined to evaluate growth properties. Fe₃ O₄ NPs (average size of 10·64 ± 4·73 nm) coated with oleic acid and synthesized by modified co-precipitation method were used. The medium pH, H⁺ efflux, membrane H⁺ conductance, redox potential determinations and H₂ yield assay were done using potentiometer methods. Growth properties were changed by NPs in concentration-dependent manner. NPs decreased (up to twofold) H⁺ -fluxes through bacterial membrane more in E. coli in the presence of the N,N'-dicyclohexylcarbodiimide, inhibitor of ATPase, indicating that antibacterial activity of these NPs was connected with ATP-associated metabolism. Membrane-associated H₂ production was lowered up to twofold. Moreover, the synergetic interactions of NPs and antibiotics were found: combination of NPs and antibiotics provided the higher H⁺ conductance, lower H⁺ -fluxes and H₂ yield.

Fe₃ O₄ NPs can be suggested as alternative antibacterial agents, which can substitute antibiotics in different applications.

The antibacterial effects of Fe₃ O₄ NPs on the growth properties and membrane activity of E. coli antibiotic-resistant strains have been demonstrated. These NPs have potential as antibacterial agents, which can substitute for antibiotics in bacterial disease treatment in biomedicine, pharmaceutical and environmental applications.