Antibacterial Activity and Toxicity of Cu(II), Ni(II) and Co(II) Sulfadiazine Complexes

Abstract

Introduction: Sulfadiazine (SDZ) was used primarily to treat urinary tract infections. Although this is fairly well tolerated, its use is associated with adverse effects. The interaction of SDZ with metallic ions, could improve its bioactive profile, which would allow to reduce the therapeutic dose and in this way the unwanted effects. Objetives: To evaluate the antibacterial activity of SDZ/Cu(II), Ni(II) and Co(II) complexes against Escherichia coli, to determine its toxicity, and to compare them with SDZ. Methodology: The E.coli ATCC 25922 was used at 2,5?105 UFC.mL-1. Minimal Inhibitory Concentration (MIC) were determined by microdilution in MH broth supplemented with Ca2+ and Mg2+.The SDZ and complexes were assayed between 2.0-0.001 μg?mL-1, and ciprofloxacin as a control. These were incubated at 37°C for 24 h. The minimal bactericidal concentration (MBC) was determined by sub-culturing aliquots of the microdilution assay on MH agar plates. These were incubated at 37°C for 24 h. Brine shrimp lethality bioassay was used to determine Lethal Concentration 50% (LC50). Results: The three complexes inhibited the growth of E. coli up to 90%, at 8 μg?mL-1, while SDZ showed MIC/MBC: 1 μg?mL-1. LC50 of Cu(II), Ni(II) and Co(II) complexes (1,000 μg?mL-1) were greater than SDZ (10 μg?mL-1). Conclusions: Significant differences among antibacterial activities of Co(II), Ni(II) and Cu(II) complexes were not observed, but yes respect to SDZ. However, the noteworthy low toxicity of complexes with respect to SDZ indicates that complexation decreases its toxicity. These results turn around to the complexes as viable alternatives, that should be tested against other microorganisms.