Modulation of antibiotic effect by Fe 2 (MoO 4 ) 3 microstrutures.

In this study, we report the antibacterial activity and modulation of antibiotic activity by Fe2 (MoO4 )3 microstructures obtained by the hydrothermal route without use of surfactants or organic additives. This material was characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) images. The XRD pattern showed that the Fe2 (MoO4 )3 crystallize in a monoclinic structure without secondary phases. Raman spectroscopy confirms the formation of Fe2 (MoO4 )3 . SEM images show that the Fe2 (MoO4 )3 obtained have ball-of-yarn shaped morphology. In the antibacterial assays, strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were assayed by microdilution method to evaluate the antibacterial and modulatory-antibiotic activity with antibiotics as gentamicin, norfloxacin and imipenem. Against all bacteria, the Minimum Inhibitory Concentration (MIC) was Fe2 (MoO4 )3  ≥ 1024 μg/mL. This high MIC result must be associated with the fact of the iron be an essential microelement to the bacterial growth. However, when the Fe2 (MoO4 )3 was assayed in association with the antibiotics was observed an antagonistic effect demonstrated by an enhance of the MIC. This fact is associated directly with the pro-oxidative properties of metallic oxides. These compounds enhance the production of free radicals, as H2 O2 and superoxide ions that can affect the cell structures as cell membrane and cell wall. Other effect is associated with the possible coordination of the metal, performing bonds with the chemical structure of the antibiotics, reducing their activity. Our results indicated that nanocompounds as Fe2 (MoO4 )3 can not be used as antimicrobial products for clinical usage, neither directly and neither in association with antibiotics.