Antimicrobial Activity of Metal-Based Danofloxacin Complexes Against Pathogenic Microorganisms

Fluoroquinolone antibiotics, like danofloxacin, are considered as crucial veterinary drugs due to their high antibacterial potential, a broad spectrum of activity and good pharmacological properties. However, owing to the widespread use of this group of pharmaceuticals, microbial resistance to them is becoming a serious worldwide concern. In the present study, novel silver and copper complexes of danofloxacin were prepared and characterized using ¹H NMR, ¹⁹F NMR and IR spectroscopy, ESI-MS spectrometry, and elemental analysis. The antimicrobial properties of the obtained complexes were determined against selected bacterial and fungal strains, including yeast and conidia-forming fungi. Additionally, toxicities of danofloxacin metal-based complex solutions were assessed toward eukaryotic cells. The obtained results indicate that silver(I) and copper(II) complexes of danofloxacin exhibit good antimicrobial activity against bacteria that are important from the veterinary point of view, like Listeria monocytogenes or Campylobacter jejuni, in concentrations which are not cytotoxic. The MBC values of metal-based danofloxacin complexes for the mentioned strains were 1.5 times lower than those obtained for danofloxacin. Additionally, the solution of the novel silver-danofloxacin complex was found to have a fungicidal effect against the studied Candida and Aspergillus strains.