New synthesized silver ultra nanoclusters (SUNc) activity against Helicobacter pylori

Introduction: Helicobacter pylori (H. pylori) infections is widely spread and still difficult to treat due to the significant increase of antibiotic resistance. Therefore, many efforts are required in order to find a new therapeutic approaches. It has been widely demonstrated that silver nanoparticles have a strong antimicrobial activity against Gram-positive and Gram-negative bacteria, as well as viruses and fungi. The aim of this study was to evaluate the antimicrobial activity of a new synthesized (EP-18181873) silver ultra-nanoclusters (SUNc) formulation against H. pylori, alone or in combination with metronidazole (MNZ). Materials and Methods: Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of SUNc were evaluated versus eight clinical H. pylori isolates with a different antibiotic susceptibility pattern, and one reference strain H. pylori ATCC 43504, using the broth microdilution methodology. The effects of combination of SUNc and MNZ were determined by checkerboard assay, and evaluated using fractional inhibitory concentration index (FICI), against 2 strains with different susceptibility to MNZ. Furthermore, the toxicity of SUNc was determined on AGS cells by using the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazoliumbromide) assay. Results: The MICs and MBCs of SUNc ranged between 0.16 to 0.33 μg/ml. The checkerboard titration assay revealed that the combination SUNc-MNZ showed a synergistic effect confirmed by a increased susceptibility to MNZ. The citotoxicity test on AGS cells demonstrated that SUNc is not toxic until 1.30 µg/ml. Conclusion: The preliminary data obtained show that SUNc are active against Helicobacter pylori and could represent, particularly in combination with MNZ, a novel strategy for the treatment of the infection associated with multidrug resistance strains.