Behnaz Shokrollahi - Department of Biology, East Tehran Branch, Islamic Azad University, Tehran, Iran
akram Sadat Tabatabaee Bafroee - Department of Biology, East Tehran Branch, Islamic Azad University, Tehran, Iran
Tayebeh Saleh - Department of Biology, East Tehran Branch, Islamic Azad University, Tehran, Iran

Background: Metal oxide nanoparticles (NPs) have shown promising efficacy for combating bacterial resistancedue to their antibacterial properties. This research investigated the effect of zinc oxide NPs (ZnO-NPs) on theantibacterial activity of conventional antibiotics including ciprofloxacin (CIP), cefotaxime (CTX), and colistin(CST) against multidrug-resistant Acinetobacter isolates.Methods: The disc diffusion method was performed to detect the pattern of antibiotic resistance in isolates. Thesynthesized ZnO-NPs via the solvothermal method were characterized by field emission scanning electronmicroscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). Finally, thebroth microdilution technique was conducted to demonstrate the antibacterial activity of CIP, CTX, and CSTantibiotics with and without a sub-inhibitory concentration of ZnO-NPs.Results: XRD, EDS, and FESEM results confirmed the crystalline structure of ZnO-NPs, and the average sizewas ۱۰۰±۵۸.۶۸ nm. All isolates were discovered to be of multidrug-resistant (MDR) type and fully susceptibleto CST. The antibacterial activity of CTX and CIP was restored when combined with a sub-inhibitory level ofZnO-NPs (۰.۲۵ mg/L), and the highest activity was obtained at the concentrations of ۳۲ μg/mL CTX and ۸ μg/mL CIP. Eventually, ZnO-NPs showed a synergistic effect on the antibacterial properties of CST against MDRAcinetobacter.Conclusions: This research indicated that the combination of ZnO-NPs with some common antibiotics can beconsidered as a novel strategy for reducing the spread of antibiotic-resistant bacteria.

Resistant Acinetobacter, Zinc oxide nanomaterials, Ciprofloxacin, Cefotaxime, Colistin, Synergisticeffect