Abstract

Antibiotic-resistant bacteria have become one of the major issues and concerns worldwide. For the past years, scientists have investigated the use of treatments in the nano-scale. Nanomaterials, such as metal oxide nanoparticles, have shown promising results due to their antibacterial properties. The aim of this study was to investigate the efficiency of in vitro antibacterial activity of zinc oxide nanoparticles (ZnO NPs) alone and in combination with different antibiotics against avian pathogenic Escherichia coli. In this study, ZnO NPs were synthesized using direct precipitation method. Physical characteristics of ZnO NPs were confirmed using X-ray diffraction and transmission electron microscopy. Antibacterial resistance pattern of 10 antibiotics including amoxicillin, ciprofloxacin, enrofloxacin, gentamicin, doxycycline, levofloxacin, trimethoprim/sulfamethoxazole, tetracycline, spiramycin, and streptomycin, in addition to different concentrations of ZnO NPs, was determined by disc diffusion method on 10 avian pathogenic E. coli (APEC). The results showed that 50% of the strains were resistant to all antibiotics, while the rest were found to be sensitive to one or two antibiotics. The best concentration of ZnO NPs was 50 mg/disk, which showed greater zones than that of other used concentrations (25, 12.5, 6.25, 3.125, and 1.56 mg/disk). The combination of spiramycin and gentamycin with ZnO NPs showed a synergistic effect while the combination of ZnO NPs with ciprofloxacin, enrofloxacin, and streptomycin showed an antagonistic effect. No antibacterial effect was observed in combination of ZnO NPs with other used antibiotics. This study recommends in vivo evaluations to confirm the results.